ELECTROMAGNETIC EFFECT MATERIAL AND CERAMIC ELECTRONIC COMPONENT

Abstract

An electromagnetic effect material includes as a primary component, a polycrystalline oxide ceramic containing at least Sr, Co, and Fe. In the polycrystalline oxide ceramic, the crystal c-axis is oriented in a predetermined direction, and the degree of orientation of the c-axis is 0.2 or more by a Lotgering method. A component substrate is formed of this electromagnetic effect material.

Claims

1.-12. (canceled)

13. An electromagnetic effect material comprising as a primary component, a polycrystalline oxide ceramic containing at least Sr, Co, and Fe, wherein in the polycrystalline oxide ceramic, a crystal c-axis is oriented in a predetermined direction.

14. The electromagnetic effect material according to claim 13, wherein the polycrystalline oxide ceramic contains at least one of Ba and at least one type of element selected from Ni, Zn, Mn, Mg, and Cu.

15. The electromagnetic effect material according to claim 13, wherein the polycrystalline oxide ceramic is (Sr.sub.1Ba.sub.).sub.3(Co.sub.1X.sub.).sub.2Fe.sub.24O.sub.41+, where X represents at least one type of element selected from Ni, Zn, Mn, Mg, and Cu, 00.4, 00.3, and 11.

16. The electromagnetic effect material according to claim 15, wherein a degree of orientation of the c-axis is 0.2 or more by a Lotgering method.

17. The electromagnetic effect material according to claim 16, wherein a degree of orientation of the c-axis is 0.6 or more by the Lotgering method.

18. The electromagnetic effect material according to claim 13, wherein a degree of orientation of the c-axis is 0.2 or more by a Lotgering method.

19. The electromagnetic effect material according to claim 18, wherein a degree of orientation of the c-axis is 0.6 or more by the Lotgering method.

20. The electromagnetic effect material according to claim 13, wherein the crystal particles of the oxide ceramic have an anisotropic shape.

21. The electromagnetic effect material according to claim 20, wherein the crystal particles have a ratio of particle lengths in longitudinal directions to particle lengths in lateral directions of 2 or more, and the longitudinal directions are crystallographically aligned in one direction.

22. The electromagnetic effect material according to claim 21, wherein the ratio is 5 or more.

23. The electromagnetic effect material according to claim 22, wherein the ratio is 10 or more.

24. The electromagnetic effect material according to claim 13, wherein electric polarization is generated by application of a magnetic field to the electromagnetic effect material and magnetization is generated by application of an electric field to the electromagnetic effect material, a polarity of the magnetization is changed in accordance with a polarity of the applied electric field, and when the electric field is changed from an application state to a non-application state, the polarity of the magnetization that is changed is retained.

25. The electromagnetic effect material according to claim 24, wherein an intensity of the magnetization is controllable in accordance with an intensity of the applied electric field.

26. The electromagnetic effect material according to claim 13, wherein electric polarization is generated by application of a magnetic field to the electromagnetic effect material and magnetization is generated by application of an electric field to the electromagnetic effect material, and an intensity of the magnetization is controllable in accordance with an intensity of the applied electric field.

27. The electromagnetic effect material according to claim 26, wherein the polarity of the magnetization is changed in accordance with the polarity of the applied electric field, and when the electric field is changed from an application state to a non-application state, the polarity of the magnetization that is changed is retained.

28. The electromagnetic effect material according to claim 13, wherein the electromagnetic effect material is used in an allowable temperature range of an electronic device.

29. The electromagnetic effect material according to claim 28, wherein the allowable temperature range is 300K50K.

30. A ceramic electronic component comprising: a component substrate; and an external electrode on a surface of the component substrate, wherein the component substrate comprises the electromagnetic effect material according to claim 13.

31. The ceramic electronic component according to claim 30, wherein the ceramic electronic component is one of a variable inductor, a nonvolatile memory, a voltage sensor, a magnetic sensor, and a magnetic switch.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1 is a front view showing one embodiment of a ceramic electronic component formed using an electromagnetic effect material of the present invention.

[0038] FIG. 2 is a perspective view schematically showing a polarization treatment device used in examples.

[0039] FIG. 3 is a perspective view showing the case in which an electromagnetic current is measured by the above polarization treatment device.

[0040] FIG. 4 is a view showing x-ray diffraction spectra of samples of Sample Nos. 5, 19, and 20.

[0041] FIG. 5 is a view showing a magnetization curve of the sample of Sample No. 5.

[0042] FIG. 6 is a view showing a magnetization curve of the sample of Sample No. 20.

[0043] FIG. 7 is a view showing one example of electric polarization characteristics of the sample of Sample No. 5.

[0044] FIG. 8 is a view showing one example of electromagnetic coupling factor characteristics of the sample of Sample No. 5.

[0045] FIG. 9 is a view showing the change in magnetization of the sample of Sample No. 5 obtained when application and non-application of an electric field are repeatedly performed.

[0046] FIG. 10 is a view showing the change in magnetization of the sample of Sample No. 5 obtained when the intensity of an applied electric field is changed.

[0047] FIG. 11 is a hysteresis curve of the sample of Sample No. 5 showing the change in magnetization with an applied electric field.

[0048] FIG. 12 is a cross-sectional image of an xy plane of the sample of Sample No. 5.

[0049] FIG. 13 is a cross-sectional image of a yz plane of the sample of Sample No. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] An electromagnetic effect material according to one embodiment of the present invention includes as a primary component, a polycrystalline oxide ceramic containing at least Sr, Co, and Fe. In addition, in the oxide ceramic described above, the crystal c-axis is oriented in a predetermined direction.

[0051] The primary component has a hexagonal Z-type crystal structure represented by the following general formula (A).

(Sr.sub.1Ba.sub.).sub.3(Co.sub.1X.sub.).sub.2Fe.sub.24O.sub.41+(A)

[0052] In the above formula, X represents at least one type of element selected from the group consisting of Ni, Zn, Mn, Mg, and Cu.

[0053] In addition, , , and satisfy equations (1) to (3), respectively.

00.4(1)

00.3(2)

1+1(3)

[0054] That is, this oxide ceramic includes a Sr.sub.3Co.sub.2Fe.sub.24O.sub.41((SrO).sub.3(CoO).sub.2(Fe.sub.2O.sub.3).sub.12)-based compound as a primary component, and if needed, also includes Ba which partially replaces Sr and an element X which partially replaces Co.

[0055] The reason is set so as to satisfy the equation (1) is that when is more than 0.4, since the content of Ba in the oxide ceramic becomes excessive, and the content of Sr is decreased, a desired large electromagnetic effect may not be obtained in some cases even if the crystal c-axis is oriented in a predetermined direction.

[0056] As is the case described above, the reason is set so as to satisfy the equation (2) is that when is more than 0.3, since the content of the element X in the oxide ceramic becomes excessive, and the content of Co is decreased, a desired large electromagnetic effect may not be obtained in some cases even if the crystal c-axis is oriented in a predetermined direction.

[0057] In addition, the reason is set so as to satisfy the equation (3) is that although represents 0 according to the stoichiometric composition, it is intended to allow the change thereof as long as the characteristics of the oxide ceramic are not adversely influenced, and is more preferably in a range of 0 to +1.

[0058] As disclosed in detail in Non-Patent Document 1, the hexagonal Z-type crystal structure described above has a complicated crystal structure in which three different types of blocks, an R block, an S block, and a T block, are laminated to each other in the order of R-S-T-S-R*-S*-T*-S*. In this structure, * indicates a block rotated by 180 with respect to the c-axis. For example, in the case of Sr.sub.3Co.sub.2Fe.sub.24O.sub.41, if the blocks are each defined by a chemical formula, the R block is formed of [SrFe.sub.6O.sub.11].sup.2, the S block is formed of Co.sub.2.sup.2+Fe.sub.4O.sub.8, and the T block is formed of Sr.sub.2Fe.sub.8O.sub.14. In addition, Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 has a multilayer structure in which the blocks described above are laminated to have a laminate cycle in the order of R-S-T-S- - - - . [0059] Non-Patent Document 1: authored by Robert C. Pullar, Hexagonal Ferrites: A review of the synthesis, properties and applications of hexaferrite ceramics, Progress in Materials Science 57, 2012, pp. 1191-1334

[0060] As a promising ferromagnetic dielectric material which can simultaneously exhibit ferromagnetism and ferroelectricity, this Sr.sub.3Co.sub.2Fe.sub.24O.sub.41-based compound having a hexagonal Z-type crystal structure has drawn attention, and by the electromagnetic effect, the electric polarization can be generated by application of a magnetic field, and the change in magnetization can also be generated by application of an electric field.

[0061] However, as disclosed in the above Technical Problem, the Sr.sub.3Co.sub.2Fe.sub.24O.sub.41-based compound described above can exhibit a practically sufficient electromagnetic effect only in a temperature region (such as 26K or less) far lower than an allowable temperature range (such as 300K50K) in which in general, electronic devices are allowed to be used.

[0062] Accordingly, through intensive research carried out by the present inventors, it was found that in the oxide ceramic described above, when the crystal c-axis is oriented in a predetermined direction, even in the allowable temperature range described above, an electromagnetic effect material capable of exhibiting preferable ferromagnetic dielectric characteristics can be obtained.

[0063] Although a method to orient the crystal c-axis is not particularly limited, for example, when a ceramic slurry formed in a manufacturing process is supplied to a mold having a predetermined shape, and the mold is then rotated while a predetermined static magnetic field (such as 0.4 to 0.5 T) is applied in one direction, the crystal orientation characteristic can be imparted to crystal particles.

[0064] The degree of this crystal orientation may be evaluated by a Lotgering method.

[0065] That is, the Lotgering method has been widely known as an index to evaluate the crystal orientation, and according to this Lotgering method, a crystal c-axis orientation degree Fc can be represented by the following equation (4).

[00001]$\begin{array}{cc}\left[\mathrm{Eq}..Math.4\right]& \\ \mathrm{Fc}=\frac{\frac{.Math..Math.I\left(00.Math.L\right)}{.Math..Math.I\left(\mathrm{hkl}\right)}-\frac{.Math..Math.\mathrm{Io}\left(00.Math.L\right)}{.Math..Math.\mathrm{Io}\left(\mathrm{hkl}\right)}}{I-\frac{.Math..Math.\mathrm{Io}\left(00.Math.L\right)}{.Math..Math.I\left(\mathrm{hkl}\right)}}& \left(4\right)\end{array}$

[0066] In the above equation, I(00L) represents the sum of x-ray peak intensity of the crystal face (00L) orthogonal to the c-axis of an oriented sample, and I(hkl) represents the sum of x-ray peak intensities of all crystal faces (hkl) of the oriented sample. In addition, I.sub.0(00L) represents the sum of x-ray peak intensity of the crystal face (00L) of a non-oriented sample, such as a standard sample, and I.sub.0(hkl) represents the sum of x-ray peak intensities of all crystal faces (hkl) of the standard sample.

[0067] In this embodiment, although the c-axis orientation degree Fc is not particularly limited as long as the crystal c-axis is oriented in a predetermined direction, in order to obtain a larger electromagnetic effect, the c-axis orientation degree Fc is preferably 0.2 or more and more preferably 0.6 or more.

[0068] In addition, although the shape of the crystal particle is not particularly limited, the crystal particles preferably have an anisotropic shape. In particular, an aspect ratio a/b of a longitudinal particle length a to a lateral particle length b is preferably 2 or more, more preferably 5 or more, and further preferably 10 or more.

[0069] In addition, the longitudinal directions of the crystal particles are preferably crystallographically aligned in one direction. In this case, the longitudinal directions are crystallographically aligned in one direction indicates the state in which 80% or more of the crystal particles form an acute angle in a range of 30 to +30 therebetween in the longitudinal directions thereof, and when the longitudinal directions of the crystal particles are crystallographically aligned in one direction as described above, a desired electromagnetic effect can be easily exhibited.

[0070] The shape of the crystal particles and the degree of alignment thereof in the longitudinal directions can be confirmed by observing a cross-sectional surface of the oxide ceramic in a predetermined direction using a laser microscope or the like. For example, when a cross-section surface orthogonal to the orientation direction of the c-axis is observed by a laser microscope, the shape anisotropy of the crystal particles can be confirmed. In addition, when a cross-sectional surface along the orientation direction of the c-axis is observed, the degree of alignment of the crystal particles in the longitudinal directions can be confirmed.

[0071] As described above, in this embodiment, since the crystal c-axis of the oxide ceramic described above is oriented in a predetermined direction, even in an allowable temperature range in which in general, electronic devices are allowed to be used, an electromagnetic effect material capable of exhibiting preferable ferromagnetic dielectric characteristics can be obtained by applying a low magnetic field.

[0072] In particular, a gigantic electromagnetic effect having an electric polarization P of 15 C/m.sup.2 or more induced by application of a magnetic field and/or an electromagnetic coupling factor of 4.010.sup.10 s/m or more can be exhibited.

[0073] That is, in a ferromagnetic dielectric material exhibiting an electromagnetic effect, since the electric polarization P is induced when spiral magnetic ordering is generated, the electric polarization P and the magnetic ordering have a close correlation therebetween, and as shown in an equation (5), when the change in electric polarization P with the change in magnetic field B is defined as an electromagnetic coupling factor , the ferromagnetic dielectric characteristics can be evaluated by the electromagnetic coupling factor .

=.sub.0(dP/dB)(5)

[0074] In the above equation, .sub.0 represent a vacuum permeability (=410.sup.7 H/m).

[0075] In addition, a current density J of an electromagnetic current I is represented by an equation (6).

J=dP/dt(6)

[0076] Accordingly, when the current density J of the electromagnetic current I is integrated with a time t, the electric polarization P can be obtained.

[0077] In addition, the change in electric polarization P with the change in magnetic field B can be represented by an equation (7).

dP/dB=(dP/dt)/(dB/dt)=J/(dB/dt)(7)

[0078] In this equation, dB/dt represents a sweeping rate of the magnetic field B.

[0079] When the above equation (5) is substituted into the equation (7), the electromagnetic coupling factor can be represented by an equation (8).

=(.sub.0.Math.J)/(dB/dt)(8)

[0080] Accordingly, the electromagnetic coupling factor can be obtained by dividing the product of the vacuum permeability .sub.0 and the current density J by the sweeping rate (dB/dt) of the magnetic field.

[0081] As apparent from the equation (8), the electromagnetic coupling factor is increased as the current density J of the electromagnetic current I is increased, and hence, the electromagnetic coupling factor is increased as the rate of change in electric polarization P is increased. As a result, a gigantic electromagnetic effect can be obtained, and a ferromagnetic dielectric can be realized.

[0082] In addition, in this electromagnetic effect material, when the crystal c-axis of the oxide ceramic is oriented in a predetermined direction as described above, an electromagnetic effect material having preferable ferromagnetic dielectric characteristics can be obtained in an allowable temperature range for electronic devices by application of a low magnetic field. The electromagnetic effect material thus obtained has an electric polarization P of 15 C/m.sup.2 or more, preferably 20 C/m.sup.2 or more, more preferably 23 C/m.sup.2 or more, and further preferably 26 C/m.sup.2 or more, and/or has an electromagnetic coupling factor of 4.010.sup.10 s/m or more, preferably 1.010.sup.9 s/m or more, and more preferably 1.510.sup.9 s/m or more.

[0083] In addition, in this electromagnetic effect material, although the primary component contains at least Sr, Co, and Fe as described above, the content of the primary component in the electromagnetic effect material described above may be at least 70 percent by weight or more, preferably 80 percent by weight or more, and more preferably 90 percent by weight or more.

[0084] In the electromagnetic effect material of the present invention, the polarity of the magnetization M is changed in accordance with the polarity of an electric field E to be applied, and in addition, when the electric field is changed from an application state to a non-application state, the polarity of the magnetization changed as described above can be retained.

[0085] For example, in the case of the hexagonal Z-type oxide ceramic described above, negative magnetization ( magnetization) is generated when a positive electric field (+electric field) is applied, and in this state, when the electric field is set to zero (non-application state), although the magnetization M closes 0, the polarity thereof is not reversed, and the negative magnetization is retained. In contrast, positive magnetization (+ magnetization) is generated when a negative electric field ( electric field) is applied, and in this state, when the electric field is set to zero (non-application state), although the magnetization M closes 0, the polarity thereof is not reversed, and the positive magnetization is retained.

[0086] In addition, in the electromagnetic effect material of the present invention, in accordance with the intensity of an electric field E to be applied, the intensity of the magnetization M can be controlled. In addition, in this case, the polarity of the magnetization M is also changed in accordance with the polarity of an electric field E to be applied, and when the electric field is changed from an application state to a non-application state, the polarity of the magnetization changed as described above can be retained.

[0087] For example, in the case of the hexagonal Z-type oxide ceramic described above, a first positive magnetization is generated by application of a first negative electric field, and in this state, even if the electric field is set to zero (non-application state), the polarity of the magnetization is not reversed, and the positive magnetization is retained as described above. In addition, the polarity of the magnetization is reversed to a negative side by application of a positive electric field, and even if the electric field is set to zero, the polarity of the magnetization is not reversed, and the negative magnetization is retained. Subsequently, when a second negative electric field having an intensity different from that of the above first negative electric field is applied, and in this state, when the electric field is set to zero (non-application state), the polarity of the magnetization is not reversed, and a second positive magnetization different from the first positive magnetization is retained.

[0088] That is, the intensity of the magnetization can be controlled in a stepwise manner in accordance with the intensity of an electric field to be applied, and even if the electric field is set to zero, the same polarity as that of the magnetization generated by application of the electric field is retained.

[0089] The reason the polarity of the magnetization is not changed even if the electric field is changed from an application state to a non-application state, and the polarity obtained in the application state can be retained is inferred that since a strong correlation between the ferroelectricity and the ferromagnetism is present, the magnetization of the oxide ceramic is changed in accordance with the intensity of an electric field to be applied, and the change in magnetization has a hysteresis with respect to a sweeping direction of the electric field. That is, it is believed that although different magnetization is generated in accordance with the intensity of an electric field to be applied, since having a hysteresis, the magnetization is not completely erased even at a zero electric field, and a remnant magnetization is generated, so that a hysteresis phenomenon occurs in which the change in magnetization as described above has a hysteresis with respect to the sweeping direction of the electric field.

[0090] In addition, although the electric resistivity of this electromagnetic effect material is not particularly limited, in order to ensure preferable insulating characteristics, in an allowable temperature range for electronic devices, the electric resistivity is preferably 1.010.sup.8 .Math.cm or more, more preferably 1.010.sup.9 .Math.cm or more, and further preferably 2.010.sup.9 .Math.cm or more.

[0091] As described above, in this embodiment, the primary component is formed of an oxide ceramic containing at least Sr, Co, and Fe, and in this oxide ceramic, the crystal c-axis is oriented in a predetermined direction. Hence, even if used in an allowable temperature range in which in general, electronic devices are allowed to be used, an electromagnetic effect material having preferable ferromagnetic dielectric characteristics can be obtained. In this electromagnetic effect material, a large electric polarization and/or electromagnetic coupling factor can be obtained by a low magnetic field, and hence, a large current can be output in response to the magnetic field, and the magnetization or the permeability can be remarkably changed by the electric field. In particular, an electromagnetic effect material can be obtained having preferable ferromagnetic dielectric characteristics in which the electric polarization P is 15 C/m.sup.2 or more and/or the electromagnetic coupling factor is 4.010.sup.10 s/m or more.

[0092] In the embodiment described above, although the oxide ceramic having a hexagonal Z-type structure with a lamination cycle in which the R block, the S block, and the T block are laminated to each other has been described in detail, a crystal system having a low crystal symmetry, such as a crystal system in which the lamination cyclic structure is partially destroyed, as compared to that the hexagonal crystal system may also be used.

[0093] In addition, there may also be used a crystal system in which an ion coordinated at a predetermined atomic position of a crystal lattice is slightly shifted therefrom and which has a low crystal symmetry as compared to that of a hexagonal crystal system. For example, in a hexagonal Z-type crystal structure, ions, such as O.sup.2 and Co.sup.2+, forming a crystal are coordinated at predetermined atomic positions defined by a space group of P6.sub.3/mmc, the space group describing the crystal symmetry. Hence, the present invention may also be applied to a crystal structure in which the ions described above are shifted from the above predetermined atomic positions and are coordinated at atomic positions defined by a different space group, and in which the crystal symmetry is lower than that of a hexagonal crystal system.

[0094] That is, in this oxide ceramic, it is important that the crystal c-axis of an oxide ceramic containing at least Sr, Co, and Fe is oriented in a predetermined direction, and hence, even by a crystal system having a crystal symmetry lower than that of a hexagonal crystal system, the desired object of the present invention can also be achieved.

[0095] Next, a method for manufacturing this electromagnetic effect material will be described in detail.

[0096] First, as ceramic raw materials, an Fe compound such as Fe.sub.2O.sub.3, an Sr compound such as SrCO.sub.3, and a Co compound such as Co.sub.3O.sub.4 are prepared together with, if needed, a Ba compound such as BaCO.sub.3 and an X compound containing an element X.

[0097] Next, those ceramic raw materials were weighed so that the above general formula (A) satisfies the equations (1) to (3).

[0098] Subsequently, the ceramic raw materials thus weighed were charged into a pulverizer, such as a pot mill, together with pulverizing media, such as partially stabilized zirconium (hereinafter referred to as PSZ) balls, a dispersant, and a solvent, such as water, and were sufficiently pulverized and mixed together, so that a mixture is obtained.

[0099] Next, after being dried and granulated, the above mixture is calcined in an air atmosphere at a temperature of 1,000 C. to 1,100 C. for a predetermined time and is then cooled to room temperature. Subsequently, pulverization is performed, so that a calcined powder is obtained.

[0100] Next, after this calcined powder is fired in an air atmosphere at a temperature of 1,150 C. to 1,250 C. for a predetermined time and are then cooled to room temperature to form a ceramic sintered body. Subsequently, this ceramic sintered body is pulverized, so that a ceramic powder is obtained.

[0101] In this step, although the powder particle diameter of this ceramic powder is not particularly limited, in order to obtain preferable orientation, the particle diameter is preferably decreased as small as possible, and the median diameter D.sub.50 is preferably 8 m or less, more preferably 4 m or less, and further preferably 2 m or less.

[0102] Next, this ceramic powder is again charged into a pulverizer together with an organic binder, such as a poly(vinyl alcohol) (hereinafter referred to as PVA), and an organic solvent, such as purified water, and is then sufficiently pulverized and mixed together, so that a ceramic slurry is obtained.

[0103] Next, after this ceramic slurry is supplied in a mold having a predetermined shape, the mold is rotated while the crystal orientation is imparted by applying a static magnetic field of 0.4 to 0.5 T in one direction, and the pressure is further applied to an axial core direction of a rotation shaft of the mold for dehydration. Subsequently, the pressure is applied in a non-magnetic field to obtain a ceramic molded body.

[0104] Next, this ceramic molded body is again fired in an air atmosphere or an oxygen atmosphere at a temperature of 1,100 C. to 1,300 C. for approximately 10 to 20 hours and is then left in an oxygen atmosphere at a temperature of 800 C. to 1,100 C. for approximately 1 to 50 hours. Subsequently, cooling is performed to room temperature for approximately 2 to 100 hours, so that an electromagnetic effect material can be formed.

[0105] As described above, since the firing is performed again, and the molded body is maintained for a predetermined time and then cooled, the electric resistivity can be increased.

[0106] Next, a ceramic electronic component using this electromagnetic effect material will be described.

[0107] FIG. 1 is a front view showing one embodiment of a variable inductor as the ceramic electronic component of the present invention.

[0108] This variable inductor includes a component substrate 1 formed of the above oxide ceramic and external electrodes 2a and 2b formed at two end portions of the component substrate 1.

[0109] In addition, this variable inductor also includes a coil so as to enable a magnetic flux to pass through the component substrate 1 when a high frequency signal flows. In particular, in this embodiment, a coil 4 formed of an electrically conductive material, such as Cu, is wound around so as to hold the external electrodes 2a and 2b.

[0110] In addition, as an electrode material forming the external electrodes 2a and 2b, any material may be used as long as having a good electrical conductivity, and for example, various types of metal materials, such as Pd, Pt, Ag, Ni, and Cu, may be used.

[0111] In this variable inductor formed as described above, since the component substrate 1 is formed of the electromagnetic effect material described above, and the coil 4 is wound around so as to hold the external electrodes 2a and 2b, when a high frequency signal is input to the coil 4, a magnetic flux generated in an arrow A direction is allowed to pass through the component substrate 1, and the inductance is obtained in accordance with the number of turns of the coil, the element shape, and the permeability of the component substrate 1. In addition, when an electric field (voltage) is applied to the external electrodes 2a and 2b, the change in magnetization (change in permeability) is generated by the electromagnetic effect, and an inductance L of the coil can be changed. In addition, when the electric field (voltage) is changed, the rate of change L in inductance L can be controlled.

[0112] The variable inductor described above may also be manufactured as described below.

[0113] That is, in the step of forming an electromagnetic effect material described above, although the crystal orientation is imparted to the ceramic slurry supplied in the mold in a rotational magnetic field, for example, when a ceramic slurry prepared by adding a ceramic powder and an organic binder to an organic solvent is formed into a sheet in a rotational magnetic field, a ceramic green sheet to which the crystal orientation is imparted may also be formed. In addition, when an internal electrode is formed if needed, a structure in which the voltage is more efficiently applied to a variable inductor can be formed.

[0114] As described above, in this embodiment, when the electric field is applied, the magnetization (permeability) can be changed, and hence, the inductance L of the coil can be changed. Furthermore, when an electric field to be applied is adjusted, the rate of change in inductance L can be controlled, so that a highly reliable variable inductance can be obtained.

[0115] Furthermore, since having preferable ferromagnetic dielectric characteristics in an allowable temperature range in which in general, electronic devices can be used, the above electromagnetic effect material may be applied to, besides the variable inductor described above, various types of ceramic electronic components, such as a nonvolatile memory, a voltage sensor, a magnetic sensor, and a magnetic switch.

[0116] For example, when the direction of the magnetization of the above electromagnetic effect material is controlled by the voltage, two types of information, that is, 0 and 1, are stored, so that this ceramic electronic component can be used as a nonvolatile memory. That is, the thickness of the electromagnetic effect material is reduced to form a thin-film substrate, electrodes are formed on two main surfaces thereof, and a tunnel magnetoresistive element is disposed on surfaces of the electrodes. In addition, when the voltage is applied to the electrodes, the polarity of the magnetization of the thin-film substrate can be reversed, and hence, in accordance with this polarity reversal of the magnetization, the resistance of the tunnel magnetoresistive element is also changed. In addition, even if the voltage application is blocked to form a non-application state, since the polarity of the magnetization of the electromagnetic effect material is not changed and is retained, the resistance of the tunnel magnetoresistive element can also be retained, so that the information can be stored.

[0117] In addition, when the voltage is applied, by the change in magnetization, the voltage can be sensed, and hence, this electromagnetic effect material can also be used as a voltage sensor.

[0118] Furthermore, this electromagnetic effect material may also be used as a low power consumption and highly sensitive magnetic sensor. That is, after this electromagnetic effect material is formed into a thin-film substrate, two electrodes are formed on two facing main surfaces of the thin-film substrate, and a current output from the electrodes or a voltage of a resistor connected to the thin-film substrate in series is measured. When the magnetic field is applied, since the current is output by the electromagnetic effect, if the current thus output is directly measured, or the voltage is measured through the resistor connected in series, the presence or absence of application of the magnetic field and the intensity thereof can be measured. In addition, since the magnetic sensor thus formed is a low power consumption type, this magnetic sensor can be expected for applications, such as a magnetic sensor of a reading head of a hard disc drive and an opening/closing sensor of a notebook personal computer or a folding type mobile phone in combination with a permanent magnet.

[0119] In addition, by the use of the polarity reversal of the magnetization, the electromagnetic effect material may also be used as a magnetic switch. For example, after the electromagnetic effect material is formed into a thin-film substrate, electrodes are formed on two main surfaces of the thin-film substrate, and a polarization treatment is then performed, so that the polarity of the magnetization in a direction orthogonal to an application direction of the electric field can be changed. That is, by the polarity reversal of the electric field, the magnetic pole of one end surface of the thin-film substrate can be changed to an S or an N polar, and by the use of this change, information can be written on a magnetic memory medium, so that the electromagnetic effect material can be used for a magnetic switch functioning as a switching element.

[0120] In addition, the present invention is not limited to the above embodiments, and it is to be naturally understood that the present invention may be variously changed and modified without departing from the scope of the present invention.

[0121] Next, examples of the present invention will be described in detail. However, the present invention is not limited to the following examples.

EXAMPLES

[0122] [Formation of Sample]

[0123] (Sample Nos. 1 to 16)

[0124] First, after a SrCO.sub.3 powder, a Co.sub.3O.sub.4 powder, and a Fe.sub.2O.sub.3 powder were prepared as ceramic raw materials and were weighed so that a composition of Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 was obtained after firing, mixing thereof was performed in an agate mortar, so that a mixed powder was obtained. Next, after this mixed powder was calcined in an air atmosphere at a temperature of 1,000 C. for 10 hours, cooling was then performed to room temperature, and mixing was performed by stirring in an agate mortar, so that a powdered sample was obtained. Subsequently, after this powdered sample was fired in an air atmosphere at a temperature of 1,160 C. to 1,190 C. for 10 to 15 hours, cooling was performed to room temperature over 19 hours, so that a ceramic sintered body was obtained.

[0125] Subsequently, this ceramic sintered body was pulverized by a ball mill, so that a ceramic powder was obtained.

[0126] The particle size distribution of the ceramic powder thus obtained was measured using a laser diffraction/scattering particle size distribution measurement apparatus (manufactured by Horiba, Ltd., La-0920), and a median diameter D.sub.50 of 4 m or less was confirmed.

[0127] Next, 2 to 3 g of the ceramic powder was added to and mixed with 1 to 2 mL of purified water prepared to contain 3 to 10 percent by weight of a PVA, so that a ceramic slurry of each of Sample Nos. 1 to 16 was formed.

[0128] Subsequently, after this ceramic slurry was supplied in a superalloy-made mold, the mold was rotated for 5 minutes while a static magnetic field of approximately 0.4 to 0.5 T was applied in one direction, and the pressure was simultaneously applied to an axial core direction of a rotation shaft for a dehydration treatment, so that the crystal orientation was imparted. Next, a pressure of 10 MPa was applied in a non-magnetic field, so that a ceramic molded body of each of Sample Nos. 1 to 16 was formed.

[0129] Subsequently, this ceramic molded body was again fired in an air atmosphere at a temperature of 1,185C for 15 hours and was then held in an oxygen atmosphere at a holding temperature of 1,000 C. for 24 hours. Next, cooling was performed to room temperature over 48 hours, so that a sample of each of Sample Nos. 1 to 16 was obtained. The exterior dimensions of the sample thus obtained were 10 mm in length, 10 mm in width, and 10 mm in thickness.

[0130] (Sample No. 17)

[0131] First, after a BaCO.sub.3 powder was prepared as a ceramic raw material besides a SrCO.sub.3 powder, a Co.sub.3O.sub.4 powder, and a Fe.sub.2O.sub.3 powder, those powders were weighed so that a composition of Sr.sub.2.6Ba.sub.0.4Co.sub.2Fe.sub.24O.sub.41 was obtained after firing. Subsequently, a ceramic powder of Sample No. 17 was formed by a method and a procedure similar to those of Sample Nos. 1 to 16 except that the firing temperature was set to 1,220 C.

[0132] Subsequently, 3 g of this ceramic powder was added to and mixed with 2 mL of purified water prepared to contain 1 percent by weight of a PVA, so that a ceramic slurry of Sample No. 17 was formed.

[0133] Subsequently, except that the holding temperature after re-firing was set to 1, 130 C., a sample of Sample No. 17 was formed by a method and a procedure similar to those of Sample Nos. 1 to 16.

[0134] (Sample No. 18)

[0135] After a mixed powder obtained by a method similar to that of Sample Nos. 1 to 16 was calcined in an air atmosphere at a temperature of 1,000 C. for 16 hours, cooling was performed to room temperature, and the mixture thus obtained was stirred and mixed together in an agate mortar. Subsequently, this powder sample was enclosed in a rubber balloon and was pressed at a hydrostatic pressure of 40 MPa, so that a cylindrical ceramic molded body having a diameter of approximately 5 mm and a length of approximately 30 mm was formed.

[0136] Next, after this ceramic molded body was fired in an oxygen atmosphere at a temperature of 1,180 C. for 16 hours, cooling was performed to room temperature over 19 hours, so that a non-oriented sample (ceramic powder) of Sample No. 18 was obtained.

[0137] (Sample No. 19)

[0138] Except that the firing temperature was set to 1,170 C., a non-oriented sample (ceramic powder) of Sample No. 19 was obtained by a method and a procedure similar to those of Sample Nos. 1 to 18.

[0139] In addition, the median diameter D.sub.50 of the sample of Sample No. 19 measured by a method and a procedure similar to those of Sample Nos. 1 to 16 was approximately 5 m.

[0140] (Sample No. 20)

[0141] First, after a BaCO.sub.3 powder, a Co.sub.3O.sub.4 powder, and a Fe.sub.2O.sub.3 powder were prepared as ceramic raw materials and were weighed so that a composition of Ba.sub.3Co.sub.2Fe.sub.24O.sub.41 was obtained after firing, mixing thereof was performed in an agate mortar, so that a mixed powder was obtained. Next, after this mixed powder was calcined in an air atmosphere at a temperature of 1,000 C. for 10 hours, cooling was performed to room temperature. Subsequently, this powder sample was enclosed in a rubber balloon and was pressed at a hydrostatic pressure of 40 MPa, so that a cylindrical ceramic molded body having a diameter of approximately 5 mm and a length of approximately 30 mm was formed.

[0142] Subsequently, firing was performed in an air atmosphere at a temperature of 1,300 C. for 15 hours, and cooling was then performed to room temperature over 10 hours, so that a ceramic sintered body was obtained. Next, this ceramic sintered body was pulverized by a ball mill, so that a ceramic powder was obtained.

[0143] Next, it was confirmed that the median diameter D.sub.50 obtained by measurement of the particle size distribution by a method and a procedure similar to those of Sample Nos. 1 to 16 was 4 m or less.

[0144] Next, 2 g of the ceramic powder was added to and mixed with 2 mL of purified water prepared to contain 5 percent by weight of a PVA, so that a ceramic slurry of Sample No. 20 was formed.

[0145] Subsequently, a ceramic molded body of Sample No. 20 was formed by a method and a procedure similar to those of Sample Nos. 1 to 16.

[0146] Subsequently, this ceramic molded body was again fired in an air atmosphere at a temperature of 1,300 C. for 15 hours and was then held in an oxygen atmosphere at a holding temperature of 1,100 C. for 24 hours. Next, cooling was performed to room temperature over 48 hours, so that a sample of Sample No. 20 was obtained. The exterior dimensions of the sample thus obtained were 10 mm in length, 10 mm in width, and 10 mm in thickness.

[0147] [Measurement of Sample Characteristics]

[0148] The primary component composition and the crystal structure of the sample of each of Sample Nos. 1 to 20 were identified, the c-axis orientation degree Fc, the electric resistivity p, the electric polarization P, and the electromagnetic coupling factor thereof were measured, and furthermore, the presence or absence of induction of the electric polarization P, and the presence or absence of the polarity reversal of the magnetization M were measured, so that the characteristics of each sample were evaluated.

[0149] For the identification of the primary component, a composition analysis was performed using an inductively coupled plasma emission spectroscopic method (ICP) and a fluorescent x-ray analytical method (XRF). In addition, the crystal structure was identified using a fluorescent x-ray analytical method.

[0150] In addition, according to the Lotgering method, since represented by the equation (4), the c-axis orientation degree Fc was obtained from an x-ray diffraction spectrum. In this case, as the standard sample, the non-oriented sample of Sample No. 18 was used.

[00002]$\begin{array}{cc}\left[\mathrm{Eq}..Math.4\right]& \\ \mathrm{Fc}=\frac{\frac{.Math..Math.I\left(00.Math.L\right)}{.Math..Math.I\left(\mathrm{hkl}\right)}-\frac{.Math..Math.\mathrm{Io}\left(00.Math.L\right)}{.Math..Math.\mathrm{Io}\left(\mathrm{hkl}\right)}}{I-\frac{.Math..Math.\mathrm{Io}\left(00.Math.L\right)}{.Math..Math.I\left(\mathrm{hkl}\right)}}& \left(4\right)\end{array}$

[0151] Since the ceramic raw materials used in this case each had a low vapor pressure, if preparation thereof was performed, for example, after the water absorption of each raw material was investigated in advance, a ceramic sintered body having a desired composition could be reproducibly obtained.

[0152] The electric resistivity p was obtained by a two-terminal method using an electrometer (manufactured by Keithley Instruments Inc., Unites States, 6517A).

[0153] Next, the sample of each of Sample Nos. 1 to 18 and 20 was cut into a thin film to form a thin-film substrate, and Ag was deposited on two main surfaces of the thin-film substrate to form surface electrodes, so that a measurement sample for characteristic evaluation was formed.

[0154] In addition, by the use of this measurement sample, the presence or absence of induction of the electric polarization P, the electric polarization P, the electric polarization P, and the electromagnetic coupling factor were measured.

[0155] FIG. 2 is a perspective view of a polarization treatment device schematically showing the direction of the electric field and that of the magnetic field in a polarization treatment, and in this FIG. 2, the case in which the application direction of the electric field is orthogonal to that of the magnetic field is shown.

[0156] That is, in this polarization treatment device, signal lines 24a and 24b are connected to a measurement sample 23 which is formed of a thin-film substrate 21 and surface electrodes 22a and 22b formed from Ag thin films and provided on two main surfaces of the substrate 21, and a direct current power source 25 is provided between the signal line 24a and the signal line 24b.

[0157] In addition, the measurement sample 23 is arranged so that when the axial core direction of the rotation shaft of the mold in orientation impartment, the thickness direction of the measurement sample 23, and the longitudinal direction thereof are each represented by a z axis, an x axis, and a y axis, respectively, an electric field E is applied in parallel with the x axis, and a magnetic field B is applied in parallel with the y axis.

[0158] In addition, a polarization treatment was performed in such a way that after a magnetic field B of 5 T was applied to the measurement sample 23 in a y axis direction, in this state, an electric field E of 1 MV/m was applied in an x axis direction, and while this electric field E was applied, the applied magnetic field was decreased to 0.5 T, and the electric field E and the magnetic field B were each then placed in a non-application state.

[0159] Next, as shown in FIG. 3, instead of using the direct current power source 25, an electrometer 26 (manufactured by Keithley Instruments Inc., United States, 6517A) was provided between the signal line 24a and the signal line 24b.

[0160] In addition, while the temperature was controlled at 300K using a low temperature cryostat (manufactured by Toyo Corp., LN-Z type), the magnetic field was swept at a rate of 1 T/min in a magnetic field range of 3 T to +3 T using the above superconducting magnet, so that a charge ejected from the measurement sample 23, that is, the electromagnetic current I, was measured by the electrometer 26.

[0161] Since the current density J of the electromagnetic current I is represented by the equation (6), the current density J was integrated with the time, so that the electric polarization P was obtained.

J=dP/dt(6)

[0162] In addition, since the electromagnetic coupling factor is represented by the equation (8), the electromagnetic coupling factor was obtained from the current density J and the sweeping rate.

=(.sub.0.Math.J/(dB/dt)(8)

[0163] In the above equation, .sub.0 represents 410.sup.7.

[0164] Subsequently, by appropriately rotating the measurement sample 23, the electric polarization P and the electromagnetic coupling factor were also obtained in the cases in each of which the application direction of the magnetic field B was in parallel with the x axis or the z axis.

[0165] As is the case described above, after the measurement sample 23 was cut so that the surface thereof orthogonal to the z axis was large and was disposed so that the application direction of the electric field E was in parallel with the z axis of the measurement sample 23, the electric polarization P and the electromagnetic coupling factor were also obtained in the cases in each of which the application direction of the magnetic field B was in parallel with the x axis direction, the y axis direction, or z axis direction of the measurement sample 23.

[0166] In addition, a sample in which the electric polarization P was induced in a magnetic field range of 2 T to +2 T was evaluated as Yes, and a sample in which the electric polarization P was not induced was evaluated as No.

[0167] Next, the presence or absence of the polarity reversal of the magnetization M of the sample of each of Sample Nos. 1 to 5, 13, 14, 17, 18, and 20 was investigated using a commercially available magnetization measurement apparatus.

[0168] That is, after a cycle in which the magnetization M was measured by application of an electric field E of +2 MV/m, was then measured at a zero electric field (non-application state), was next measured after 30 seconds passed, by application of an electric field of 2 MV/m, and was further measured again at a zero electric field was repeatedly performed several times, the polarity of the magnetization M with respect to the application of the electric field E was confirmed.

[0169] In addition, in the case in which after an electric field of +2 MV/m was applied, the electric field was set to zero and the case in which after an electric field of 2 MV/m was applied, the electric field was set to zero, if the polarity of the magnetization M was reversed from a positive side to a negative side or from a negative side to a positive side, the polarity reversal of the magnetization M was evaluated as Yes, and when the polarity of the magnetization M was not reversed, the polarity reversal was evaluated as No.

[0170] In addition, electric fields having different intensities were successively applied, and the change in magnetization M was investigated. That is, after an electric field E of 2.0 MV/m was applied, the electric field was set to zero and was held for approximately 10 seconds, and subsequently, after an electric field E of +2.0 MV/m was applied, the electric field was set to zero and was held for approximately 10 seconds. Next, as in the case described above, different electric fields E of 1.67 MV/m, 1.17 MV/m, 0.67 MV/m, and 0.33 mV/m were successively applied, and the relationship between the electric field E and the magnetization M was investigated.

[0171] Table 1 shows manufacturing conditions of the sample of each of Sample Nos. 1 to 20.

[0172] In addition, Table 2 shows the measurement results of the sample of each of Sample Nos. 1 to 20 in the state shown in FIG. 2, that is, in the state in which the application direction of the magnetic field B is orthogonal to the direction of the electric polarization P (BP), the application direction of the magnetic field B is in parallel with the y axis (B//y), and the electric polarization P is in parallel with the x axis (P//x)). In Table 2, the electric polarization P and the electromagnetic coupling factor represent the peak values of the electric polarization characteristics and the electromagnetic coupling factor characteristics, respectively, which will be described later.

TABLE-US-00001 TABLE 1 Ceramic Powder Ceramic Slurry Firing Powder Water PVA Content Intensity of Static Holding Sample Primary Component Temperature Weight Volume in Water Magnetic Field Temperature No. Composition ( C.) (g) (mL) (wt %) (T) ( C.) 1 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1170 3 2 3 0.4 1000 2 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1170 3 2 3 0.4 1000 3 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1170 3 2 3 0.4 1000 4 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1170 3 2 3 0.4 1000 5 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1180 2 2 5 0.4 1000 6 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1165 3 2 3 0.4 1000 7 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1165 3 2 3 0.4 1000 8 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1160 3 2 3 0.4 1000 9 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1165 3 2 3 0.4 1000 10 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1160 3 2 3 0.4 1000 11 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1160 3 2 3 0.4 1000 12 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1160 3 2 3 0.4 1000 13 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1190 2 1 7 0.4 1000 14 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1190 2 1 10 0.4 1000 15 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1180 3 2 3 0.4 1000 16 Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1180 3 2 3 0.4 1000 17 Ba.sub.0.4Sr.sub.2.6Co.sub.2Fe.sub.24O.sub.41 1220 3 2 1 0.5 1130 18* Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1180 19* Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 1170 20* Ba.sub.3Co.sub.2Fe.sub.24O.sub.41 1300 2 2 5 0.4 1100 *is outside of the present invention.

TABLE-US-00002 TABLE 2 Presence or Presence or Absence of Absence of c-Axis Electric Induction of Electric Electromagnetic Polarity Sample Orientation Resistiity Electric Polarization Coupling Factor Reversal of No. Degree Fc ( .Math. cm) Polarization P P (C/m.sup.2) (s/m) Magnetization M 1 0.947 2.23 10.sup.9 Yes 26.1 1.05 10.sup.9 Yes 2 0.930 1.45 10.sup.9 Yes 24.3 1.19 10.sup.9 Yes 3 0.910 1.93 10.sup.9 Yes 28.0 1.25 10.sup.9 Yes 4 0.898 2.87 10.sup.9 Yes 27.0 1.07 10.sup.9 Yes 5 0.872 6.19 10.sup.8 Yes 27.6 1.48 10.sup.9 Yes 6 0.859 1.46 10.sup.9 Yes 20.1 .sup.8.32 10.sup.10 Not Measured 7 0.842 3.92 10.sup.9 Yes 26.3 1.29 10.sup.9 Not Measured 8 0.832 3.04 10.sup.9 Yes 27.2 1.25 10.sup.9 Not Measured 9 0.792 5.28 10.sup.9 Yes 24.6 1.48 10.sup.9 Not Measured 10 0.729 5.13 10.sup.8 Yes 26.7 .sup.9.20 10.sup.10 Not Measured 11 0.722 4.68 10.sup.8 Yes 25.0 .sup.8.16 10.sup.10 Not Measured 12 0.707 7.38 10.sup.8 Yes 22.8 1.00 10.sup.9 Not Measured 13 0.654 1.53 10.sup.9 Yes 22.8 1.02 10.sup.9 Yes 14 0.509 1.07 10.sup.9 Yes 16.0 .sup.5.94 10.sup.10 Yes 15 0.278 7.83 10.sup.9 Yes 15.6 .sup.7.87 10.sup.10 Not Measured 16 0.272 4.08 10.sup.9 Yes 17.3 .sup.4.66 10.sup.10 Not Measured 17 0.931 5.54 10.sup.7 Yes 23.3 .sup.9.05 10.sup.10 Yes 18* 0 1.24 10.sup.9 Yes 10.4 .sup.2.59 10.sup.10 No 19* 0 20* 0.812 2.98 10.sup.9 No 0 0 No *is outside of the present invention.

[0173] [Evaluation of Sample]

[0174] (Identification of Primary Component Composition and Crystal Structure)

[0175] According to the results of the composition analysis by an ICP-XRF method, it was confirmed that the component composition of the primary component was as shown in Table 2. In addition, it was also confirmed that from the x-ray diffraction spectra, the crystal structures were each a hexagonal Z-type structure.

[0176] (c-Axis Orientation Degree)

[0177] It was found that the samples of Sample Nos. 1 to 17 and 20 to each of which the crystal orientation was imparted were oriented in a range of 0.272 to 0.947 in terms of the c-axis orientation degree Fc.

[0178] Although the relationship between the c-axis orientation degree Fc and the manufacturing conditions has not been clearly understood, it was found that the sample of each of Sample Nos. 1 to 4 in which the firing was performed at a temperature of 1,170 C. had a high c-axis orientation degree Fc, and that when the firing temperature was higher or lower than 1,170 C., the c-axis orientation degree Fc tended to decrease.

[0179] Since the sample of Sample No. 18 was a non-oriented sample, and the sample of Sample No. 19 was a powder sample, the c-axis orientation degree Fc was 0.

[0180] FIG. 4 shows x-ray diffraction spectra of the samples of Sample Nos. 5, 19, and 20.

[0181] In the figure, Sample No. 5-1a and 20-1a were each disposed for measurement so that x-rays to be radiated were reflected on an xy plane of the measurement sample, and Sample No. 5-1b and 20-2b were each disposed for measurement so that x-rays to be radiated were reflected on an xz plane of the measurement sample.

[0182] In the cases described above, the x axis, the y axis, and the z axis are the same as those shown in FIGS. 2 and 3, the z axis represents the axial core direction of the rotation shaft of the mold in crystal orientation impartment, the xy plane represents a plane that includes no z axis and is orthogonal thereto, the xz plane represents a plane formed by the x axis and the z axis, and the yz plane represents a plane formed by the y axis and the z axis.

[0183] In addition, in the figure, the marks shown under Sample Nos. 5-1a and 20-1a each indicate a reflection position of the crystal face (00L) expected from a hexagonal Z-type crystal structure, and the marks x shown under Sample Nos. 5-2a and 20-2a each indicate a reflection position of the crystal face (HK0) expected from a hexagonal Z-type crystal structure. In addition, the values, such as (110) and (200), in the x-ray spectra each indicate the crystal face at which the peak intensity is detected in the x-ray spectrum.

[0184] In addition, Sample No. 19 indicates an x-ray spectrum of the sample in the form of a powder.

[0185] From this FIG. 4, the c-axis orientation degree Fc was obtained using the non-oriented sample of Sample No. 18 as a standard sample, and as shown in Table 2, the c-axis orientation degree Fc of the sample of Sample No. 5 was 0.872, and that of the sample of Sample No. 20 was 0.812.

[0186] FIG. 5 shows magnetization curves of the sample of Sample No. 5 at 300K. The horizontal axis represents the magnetic field B (T), and the vertical axis represents the magnetization M (B/f.u.) per formula unit of the sample. In the figure, Sample No. 5-2a shows the case in which the application direction of the magnetic field B is orthogonal to the z axis of the sample (Bz), and Sample No. 5-2b shows the case in which the application direction of the magnetic field B is in parallel with the z axis of the sample (B//z).

[0187] As apparent from this FIG. 5, it was found that the sample of Sample No. 5 had different magnetization curves depending on the application direction of the magnetization and had a magnetic anisotropy. That is, the sample of Sample No. 5 had a magnetic anisotropy, and from the magnetization curves described above, it was found that a high orientation degree (Fc: 0.872) as shown in Table 2 was obtained.

[0188] FIG. 6 shows magnetization curves of the sample of Sample No. 20 at 300K. The horizontal axis represents the magnetic field B (T), and the vertical axis represents the magnetization M (B/f.u.) per formula unit of the sample. In the figure, Sample No. 20-2a shows the case in which the application direction of the magnetic field B is orthogonal to the z axis of the sample (Bz), and Sample No. 20-2b shows the case in which the application direction of the magnetic field B is in parallel with the z axis of the sample (B//z).

[0189] As apparent from this FIG. 6, it was found that the sample of Sample No. 20 had different magnetization curves depending on the application direction of the magnetization and had a magnetic anisotropy. That is, the sample of Sample No. 20 also had a magnetic anisotropy, and from the magnetization curves described above, it was found that a high orientation degree (Fc: 0.812) as shown in Table 2 was obtained.

[0190] (Ferromagnetic Dielectric Characteristics)

[0191] As apparent from Table 2, since Sr was not contained in the sample of Sample No. 20, although the sample had a magnetic anisotropy, the electric polarization P was not induced, and as a result, the electric polarization P and the electromagnetic coupling factor could not be obtained.

[0192] In contrast, since at least Sr, Co, and Fe were contained in the samples of Sample Nos. 1 to 18, when the magnetic field B was applied in a magnetic field range of 2 T to +2 T, the electric polarization P was induced, and as a result, the electric polarization P and the electromagnetic coupling factor could be obtained.

[0193] However, since the sample of Sample No. 18 was a non-oriented sample in which the crystal axis of the crystal particles was not c-axis oriented, the electric polarization P and the electromagnetic coupling factor both were small, such as 10.4 C/m.sup.2 and 2.5910.sup.10 s/m, respectively.

[0194] In contrast, in the samples of Sample Nos. 1 to 17, since the crystal axis of the crystal particles was c-axis oriented, a preferable electric polarization P of 15 C/m.sup.2 or more, in particular, of 15.6 to 26.1 C/m.sup.2, could be obtained, and a preferable electromagnetic coupling factor of 4.010.sup.10 s/m or more, in particular, of 4.6610.sup.10 to 1.0010.sup.9 s/m, could be obtained. Specifically, it was found that when the c-axis orientation degree Fc was 0.6 or more, a large electric polarization P of 20 C/m.sup.2 or more and a large electromagnetic coupling factor of 8.010.sup.10 s/m or more could be obtained.

[0195] FIG. 7 shows the electric polarization characteristics of the sample of Sample No. 5 obtained when the magnetic field was applied in a magnetic field range of 0.5 T to +2 T and when the direction of the electric polarization P was in parallel with the x axis of the sample (P//x). The horizontal axis represents the magnetic field B (T), and the vertical axis represents the electric polarization P (C/m.sup.2).

[0196] In the figure, Sample No. 5-3a shows the case in which the application direction of the magnetic field B is in parallel with the x axis of the sample (B//x), Sample No. 5-3b shows the case in which the application direction of the magnetic field B is in parallel with the y axis of the sample (B//y), and Sample No. 5-3c shows the case in which the application direction of the magnetic field B is in parallel with the z axis of the sample (B//z).

[0197] In addition, the electric polarization P of the sample of Sample No. 5 in Table 2 corresponds to that of Sample No. 5-3b.

[0198] As apparent from this FIG. 7, it was found that Sample No. 5-3a (B//x) could obtain a larger electric polarization P than that of each of Sample No. 5-3b (B//y) and Sample No. 5-3c (B//z).

[0199] FIG. 8 shows the electromagnetic coupling factor characteristics of the sample of Sample No. 5 obtained when the magnetic field was applied in a magnetic field range of 3 T to +3 T and when the direction of the electric polarization P was in parallel with the x axis of the sample (P//x). The horizontal axis represents the magnetic field B (T), and the vertical axis represents the electromagnetic coupling factor 10.sup.9 (s/m).

[0200] As the case shown in FIG. 7, Sample No. 5-3a shows the case in which the application direction of the magnetic field B is in parallel with the x axis of the sample (B//x), Sample No. 5-3b shows the case in which the application direction of the magnetic field B is in parallel with the y axis of the sample (B//y), and Sample No. 5-3c shows the case in which the application direction of the magnetic field B is in parallel with the z axis of the sample (B//z).

[0201] In addition, the electromagnetic coupling factor of the sample of Sample No. 5 in Table 2 corresponds to that of the Sample No. 5-3b.

[0202] As apparent from this FIG. 8, it was found that Sample No. 5-3b (B//y) could obtain a larger electric polarization P than that of each of Sample No. 5-3a (B//x) and Sample No. 5-3c (B//z).

[0203] Table 3 shows the ferromagnetic dielectric characteristics of Sample Nos. 5-3a and 5-3b.

TABLE-US-00003 TABLE 3 Directional Relationship between Application Magnetic Field Direction of Direction of Magnetic Electric Electromagnetic Sample B and Electric Magnetic Electric Field B Polarization Coupling Factor No. Polarization P Field B Polarization P (T) P (C/m.sup.2) (s/m) 5-3a Parallel Parallel Parallel 0.41 30.0 3.49 10.sup.10 with x Axis with x Axis 5-3b Orthogonal Parallel Parallel 0.214 27.6 1.48 10.sup.9 with y Axis with x Axis

[0204] As apparent from this Table 3, in comparison between Sample No. 5-3a ((BP), (B//x)) and Sample No. 5-3b ((B//P), (B//y)), the electric polarization P of Sample No. 5-3a was 30.0 C/m.sup.2 which was larger than that of Sample No. 5-3b, and the electromagnetic coupling factor of Sample No. 5-3b was 1.4810.sup.9 s/m which was larger than that of Sample No. 5-3a. In both cases, the results are approximately equivalent to those of a single crystal of Sr.sub.3Co.sub.2Fe.sub.24O.sub.41 which has been already reported in Non-Patent Document 2. [0205] Non-Patent Document 2: Sae Hwan Chun, et al., Electric Field Control of Nonvolatile Four-State Magnetization at Room Temperature, Physical Review Letters, 108, 177201 (2012)

[0206] Although the formation of a single crystal takes time and cost, it was found in the present invention that by the electromagnetic effect in which the electric polarization is induced by a magnetic field, a polycrystalline oriented oxide ceramic exhibiting excellent performance almost equivalent to that of a single crystal can be easily realized.

[0207] [Magnetization Characteristics]

[0208] FIG. 9 shows the change in magnetization obtained in such a way that after a positive electric field of +2 MV/m and a negative electric field of 2 MV/m are applied to the sample of Sample No. 5, the electric field was set to zero (non-application state). The horizontal axis represents a time t (s), and the vertical axis represents the magnetization M (B/f.u.) per formula unit.

[0209] As apparent from this FIG. 9, when an electric field of +2 MV/m.sup.2 is applied, a negative polar magnetization M is generated, and even when the electric field E is not applied and set to zero, a magnetization M of 0.002 B/f.u. remains due to the influence of the remnant magnetization, and the negative polarity of the magnetization M is retained without polarity reversal.

[0210] Next, when an electric field of 2 MV/m.sup.2 is applied, a positive polar magnetization M is generated. In addition, even when the electric field E is not applied and set to zero, a magnetization M of approximately +0.002 B/f.u. remains due to the influence of the remnant magnetization, and the positive polarity of the magnetization is retained without polarity reversal.

[0211] It was confirmed that the polarity of the magnetization M is changed in accordance with the polarity of the electric field E to be applied as described above, and that when the electric field E is changed from an application state to a non-application state, the polarity of the magnetization that is changed as described above is retained.

[0212] In addition, FIG. 10 shows the change in magnetization of the sample of Sample No. 5 obtained when different electric fields are applied in a stepwise manner. The horizontal axis represents a time t (s), and the vertical axis represents the magnetization M (B/f.u.) per formula unit.

[0213] That is, when an electric field E of 2.0 MV/m.sup.2 is applied and then set to zero, a positive polar magnetization M of approximately +0.003 to 0.004 B/f.u. remains. In addition, when an electric field E of +2.0 MV/m is applied, the polarity is reversed, and a negative magnetization M is generated. Subsequently, even if the electric field E is set to zero, due to the influence of the remnant magnetization, a magnetization M of approximately 0.0015 B/f.u. remains, and hence the negative polarity is retained without polarity reversal. Subsequently, when an electric field of 1.67 MV/m is applied, the polarity of the magnetization is reversed, and when the electric field is set to zero, a positive polar magnetization M of approximately +0.003 to 0.004 B/f.u. remains. In addition, when an electric field of +2.0 MV/m is applied, the polarity of the magnetization is again reversed, and when the electric field is set to zero, a magnetization of approximately 0.0015 B/f.u. remains. Subsequently, when an electric field of 1.17 MV/m is applied, the polarity of the magnetization is reversed, and when the electric field is set to zero, the magnetization M is decreased in accordance with the intensity of the applied electric field E, and a positive polar magnetization M of approximately +0.0025 B/f.u. is obtained. Hereinafter, in a manner similar to that described above, when the positive applied electric field is set constant at +2.0 MV/m, and the negative applied electric field is changed to 0.67 MV/mm and 0.33 mV/m, the magnetization M at a zero electric field is changed in a stepwise manner in accordance with the intensity of the applied electric field, and even if the electric field is set to zero, the polarity of the magnetization obtained by the application of the electric field is still retained.

[0214] In the case in which the intensity of an applied electric field is successively changed as described above, it was found that when the electric field is set to zero, the magnetization is changed in accordance with the intensity of the applied electric field.

[0215] FIG. 11 shows the relationship between the electric field and the change in magnetization of the sample of Sample No. 5. The horizontal axis represents the electric field E (MV/m), and the vertical axis represents the change M (.sub.B/f.u.) of the magnetization.

[0216] A polarization treatment was performed by applying a voltage of 300 V at a temperature of 300K and an applied magnetic field of +3 T, and while a magnetic field of 1.5 mT was applied at a temperature of 300K, sweeping was performed in an electric field range of 1 to +1 MV/m.

[0217] As apparent from this FIG. 11, it was found that in accordance with the intensity of the applied electric field, the magnetization was changed, and the change in magnetization had a hysteresis in an electric field sweeping direction. In addition, it is believed that by the control of the intensity of the applied electric field using this hysteresis phenomenon, the polarity of the magnetization after the application of an electric field can be controlled.

[0218] [Observation of Crystal Particles]

[0219] FIGS. 12 and 13 each show a cross-sectional image of the sample of Sample No. 5 taken by a laser microscope, FIG. 12 shows a cross-sectional image of an xy plane of the sample, and FIG. 13 is a cross-sectional image of a yz plane thereof.

[0220] As apparent from FIGS. 12 and 13, it was found that the crystal particles had an anisotropic shape, and the longitudinal directions thereof were aligned in one direction. In addition, in the sample of Sample No. 5, the aspect ratio of the crystal particles was 4 to 25.

[0221] The electromagnetic effect material of the present invention can exhibit preferable ferromagnetic dielectric characteristics in an allowable temperature range in which in general, electronic devices are allowed to be used and can be applied to ceramic electronic components, such as a variable inductor, a nonvolatile memory, a magnetic sensor, a voltage sensor, and a magnetic switch.

REFERENCE SIGNS LIST

[0222] 1 component substrate [0223] 2a, 2b external electrode