MAGNETORESISTANCE EFFECT ELEMENT AND MAGNETIC MEMORY

Abstract

A magnetoresistance effect element includes first and second magnetic layers having a perpendicular magnetization direction, and a first non-magnetic layer disposed adjacent to the first magnetic layer and on a side opposite to a side on which the second magnetic layer is disposed. An interfacial perpendicular magnetic anisotropy exists at an interface between the first magnetic layer and the first non-magnetic layer, and the anisotropy causes the first magnetic layer to have a magnetization direction perpendicular to the surface of the layers. An atomic fraction of all magnetic elements to all magnetic and non-magnetic elements included in the second magnetic layer is smaller than that of the first magnetic layer.

Claims

1. A magnetoresistance effect element, comprising: a first magnetic layer having a magnetization direction perpendicular to a surface of the first magnetic layer, the first magnetic layer containing at least one 3d ferromagnetic transition metal element; a first non-magnetic layer adjacent to the first magnetic layer; and a second magnetic layer disposed adjacent to the first magnetic layer on a side opposite to the first non-magnetic layer, the second magnetic layer having a magnetization direction parallel to the magnetization direction of the first magnetic layer, the second magnetic layer containing at least one 3d ferromagnetic transition metal element, wherein an atomic fraction of all magnetic elements to all magnetic and non-magnetic elements included in the second magnetic layer is smaller than an atomic fraction of all magnetic elements to magnetic and non-magnetic elements included in the first magnetic layer.

2. The magnetoresistance effect element according to claim 1, wherein the first magnetic layer and the second magnetic layer respectively contain boron (B), and a boron composition of the first magnetic layer is smaller than a boron composition of the second magnetic layer.

3. The magnetoresistance effect element according to claim 1, wherein the first magnetic layer contains cobalt (Co) or iron (Fe), and the second magnetic layer contains boron (B), and contains cobalt (Co) or iron (Fe).

4. The magnetoresistance effect element according to claim 1, wherein the first magnetic layer contains iron (Fe), and the second magnetic layer contains iron (Fe) and vanadium (V).

5. The magnetoresistance effect element according to claim 2, wherein the first magnetic layer contains cobalt (Co) or iron (Fe), and the second magnetic layer contains boron (B), and contains cobalt (Co) or iron (Fe).

6. The magnetoresistance effect element according to claim 2, wherein the first magnetic layer contains iron (Fe), and the second magnetic layer contains iron (Fe) and vanadium (V).

7. The magnetoresistance effect element according to claim 1, wherein the second magnetic layer has a thickness greater than that of the first magnetic layer.

8. The magnetoresistance effect element according to claim 1, further comprising: a third magnetic layer disposed adjacent to the second magnetic layer on a side opposite to the first magnetic layer, the third magnetic layer having a magnetization direction parallel to the magnetization direction of the first magnetic layer, the third magnetic layer containing at least one 3d ferromagnetic transition metal element; and a second non-magnetic layer disposed adjacent to the third magnetic layer on a side opposite to the second magnetic layer.

9. The magnetoresistance effect element according to claim 8, wherein the second magnetic layer is thicker than each of the first and third magnetic layers.

10. The magnetoresistance effect element according to claim 8, wherein the atomic fraction of all magnetic elements to all magnetic and non-magnetic elements included in the second magnetic layer is smaller than each of the atomic fraction of all magnetic elements to all magnetic and non-magnetic elements included in the first magnetic layer and an atomic fraction of all magnetic elements to all magnetic and non-magnetic elements included in the third magnetic layer.

11. The magnetoresistance effect element according to claim 8, wherein the second magnetic layer has a boron composition greater than any boron compositions of the first and third magnetic layers.

12. The magnetoresistance effect element according to claim 8, wherein the first, second and third magnetic layers each contain at least one non-magnetic element, and the second magnetic layer has a non-magnetic element composition greater than any non-magnetic element compositions of the first and third magnetic layers.

13. The magnetoresistance effect element according to claim 8, wherein the second magnetic layer has a multi-layer structure including fourth and fifth magnetic layers, and a third non-magnetic layer disposed between the fourth and fifth magnetic layers, and the fourth and fifth magnetic layers each contain at least one 3d ferromagnetic transition metal element.

14. The magnetoresistance effect element according to claim 13, wherein a combined thickness of the fourth and fifth magnetic layers is equal to or greater than a combined thickness of the first and third magnetic layers.

15. The magnetoresistance effect element according to claim 13, wherein the fourth and fifth magnetic layers each have a boron composition greater than any boron composition of each of the first and third magnetic layers.

16. The magnetoresistance effect element according to claim 1, further comprising: a second non-magnetic layer disposed on one side of the second magnetic layer opposite to another side on which the first magnetic layer is disposed; and two reference layers, each of which is disposed on either one side of the first non-magnetic layer opposite to another side on which the first magnetic layer is disposed or one side of the second non-magnetic layer opposite to another side on which the second magnetic layer is disposed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0062] FIGS. 1A and 1B are perpendicular cross-sectional views showing a recording layer of a magnetoresistance effect element of an embodiment of the invention.

[0063] FIG. 2A is a graph showing the Ms-B ratio characteristics of the magnetoresistance effect element, and FIG. 2B is a graph showing the K.sub.i-B ratio characteristics of the magnetoresistance effect element.

[0064] FIG. 3 is a graph showing a relationship between the thermal stability index E/k.sub.BT and the saturation magnetization Ms.

[0065] FIG. 4 is a perpendicular cross-sectional view showing Embodiments 1 and 2 of the magnetoresistance effect element of the invention.

[0066] FIG. 5 is the first graph by simulation showing the relationship between the thermal stability and the interfacial magnetic anisotropy energy density K.sub.i characteristics of the magnetoresistance effect element of an embodiment of the invention.

[0067] FIGS. 6A and 6B are the second graphs by simulation showing the relationship between the thermal stability and the interfacial magnetic anisotropy energy density K.sub.i characteristics of the magnetoresistance effect element of an embodiment of the invention.

[0068] FIG. 7 is a perpendicular cross-sectional view showing Embodiment 3 of the magnetoresistance effect element of the invention.

[0069] FIG. 8 is a perpendicular cross-sectional view showing Embodiment 4 of the magnetoresistance effect element of the invention.

[0070] FIG. 9 is a perpendicular cross-sectional view showing Embodiment 5 of the magnetoresistance effect element of the invention.

[0071] FIG. 10 is a perpendicular cross-sectional view showing Embodiment 6 of the magnetoresistance effect element of the invention.

[0072] FIG. 11 is a perpendicular cross-sectional view showing Embodiment 7 of the magnetoresistance effect element of the invention.

[0073] FIG. 12 is a circuit block diagram showing the magnetic memory of an embodiment of the invention.

[0074] FIG. 13A is a graph showing the relationship between the Fe layer thickness and the interfacial magnetic anisotropy energy density K.sub.i characteristics, and FIG. 13B is a graph showing the relationship between the Fe layer thickness and the damping constant characteristics of the magnetoresistance effect element of Embodiment 2 of the invention.

[0075] FIG. 14 is a circuit diagram showing a magnetic memory cell of a magnetic memory having a conventional magnetoresistance effect element.

[0076] FIG. 15A is a perpendicular cross-sectional view of a conventional perpendicular magnetic anisotropy magnetoresistance effect element, FIG. 15B is a perpendicular cross-sectional view of another conventional perpendicular magnetic anisotropy magnetoresistance effect element, and FIG. 15C is a perpendicular cross-sectional view of yet another conventional perpendicular magnetic anisotropy magnetoresistance effect element.

DETAILED DESCRIPTION OF THE INVENTION

[0077] Below, embodiments of the invention will be explained with reference to the figures.

Embodiment 1

[0078] FIG. 4 shows a magnetoresistance effect element having a structure including two non-magnetic layers as an embodiment of the invention.

[0079] As shown in FIG. 4, the magnetoresistance effect element (10) has a multilayer structure made of a lower non-magnetic electrode (14), a first reference layer (24), a first non-magnetic layer (13), a first recording layer (19), a second non-magnetic layer (18), and an upper non-magnetic electrode (15). The first non-magnetic layer (13) is a barrier layer (tunnel junction layer) of the magnetoresistance effect element, and the second non-magnetic layer (18) is a protective layer.

[0080] The first reference layer (24) has a multilayer structure made of an eighth magnetic layer (22), a fifth non-magnetic layer (23), a seventh magnetic layer (20), a fourth non-magnetic layer (21), and a sixth magnetic layer (11). The first recording layer (19) has a multilayer structure made of a first magnetic layer (25), a second magnetic layer (12), and a third magnetic layer (17).

[0081] (Lower Non-Magnetic Electrode 14)

[0082] The lower non-magnetic electrode (14) is connected to an end surface of the eighth magnetic layer (22), which is opposite to the end surface in contact with the fifth non-magnetic layer (23). Specifically, the lower non-magnetic electrode (14) has a multilayer structure of Sub/Ta(5 nm)/Ru(5 nm)/Ta(10 nm)/Pt(5 nm).

[0083] (Seventh Magnetic Layer 20, Eighth Magnetic Layer 22).

[0084] The seventh magnetic layer (20) and the eighth magnetic layer (22) are made of a material that contains at least one 3d ferromagnetic transition metal such as Co, Fe, Ni, and Mn. The seventh magnetic layer (20) and the eighth magnetic layer (22) may be made of an alloy film or multilayer film having the perpendicular magnetization easy axis, or may be made of an alloy film or multilayer film given the perpendicular magnetization easy axis from the shape magnetic anisotropy by making the film thickness of each film larger than the junction size. In a specific example, the eighth magnetic layer 22 is [Co (0.5 nm)/Pt (0.3 nm)]6.5 layers, and the seventh magnetic layer 20 is [Co (0.5 nm)/Pt (0.3 nm)]2.5 layers.

[0085] (Fifth Non-Magnetic Layer 23)

[0086] The fifth non-magnetic layer 23 is made of a material that includes one of Ru, Rh, Ir, Cr, and Cu. If the magnetization of the seventh magnetic layer 20 and the magnetization of the eighth magnetic layer 22 are anti-parallel, the fifth non-magnetic layer 23 does not need to be made of such a material. In a specific example, the fifth non-magnetic layer 23 is made of Ru (0.4 nm).

[0087] (Fourth Non-Magnetic Layer 21)

[0088] The fourth non-magnetic layer 21 is magnetically coupled with the adjacent seventh magnetic layer (20) and sixth magnetic layer (11), and is made of a material including at least one of Ta, W, Hf, Zr, Nb, Mo, Ti, V, and Cr. However, the fourth non-magnetic layer 21 does not need to be made of such a material if the fourth non-magnetic layer 21 can form magnetic coupling between the seventh magnetic layer (20) and the sixth magnetic layer (11). In a specific example, the fourth non-magnetic layer 21 is made of Ta (0.3 nm).

[0089] (Sixth Magnetic Layer 11)

[0090] The sixth magnetic layer (11) is made of a material that contains at least one 3d ferromagnetic transition metal such as Co, Fe, Ni, and Mn. In a specific example, the sixth magnetic layer (11) is made of CoFeB (1.2 nm).

[0091] (First Non-Magnetic Layer 13, Second Non-Magnetic Layer 18)

[0092] Respective end faces of the first non-magnetic layer 13 are in contact with the sixth magnetic layer (11) and the first magnetic layer (25). Respective end faces of the second non-magnetic layer (18) are in contact with the third magnetic layer (17) and the upper non-magnetic layer (15).

[0093] The first non-magnetic layer (13) and the second non-magnetic layer (18) are made of a material having a compound containing oxygen such as MgO, Al.sub.2O.sub.3, SiO.sub.2, TiO, and Hf.sub.2O so that a larger magnetoresistance change rate is obtained when combined with the material of the sixth magnetic layer (11) and the first magnetic layer (25). In a specific example, the first non-magnetic layer (13) and the second non-magnetic layer (18) are made of MgO (1.2 nm). Alternatively, the first non-magnetic layer (13) may be made of MgO (1.2 nm) and the second non-magnetic layer (18) may be made of MgO (1.0 nm) with different film thicknesses.

[0094] (Third Magnetic Layer 17, First Magnetic Layer 25).

[0095] It is preferable that the third magnetic layer (17) and the first magnetic layer (25) be made of a material that contains at least one 3d ferromagnetic transition metal such as Co, Fe, Ni, and Mn. The third magnetic layer (17) and the first magnetic layer (25) do not contain B and the second magnetic layer (12) contains B, or the ratio of the composition of boron B in the third magnetic layer (17) to the composition of boron B in the second magnetic layer (12) is smaller than 1, and the ratio of the composition of boron B in the first magnetic layer (25) to the composition of boron B in the second magnetic layer (12) is smaller than 1.

[0096] In a specific example, the third magnetic layer (17) and the first magnetic layer (25) are each made of CoFe (0.4 nm to 1 nm).

[0097] (Second Magnetic Layer 12)

[0098] The second magnetic layer (12) is made of a material that contains at least one 3d ferromagnetic transition metal such as Co, Fe, Ni, and Mn. In order to increase K.sub.efft, the material with low saturation magnetization Ms is to be used except for the interface portion. In a specific example, the second magnetic layer (12) is made of CoFeB (0.4 nm to 5 nm). It is also possible to make CoFeB thicker than 5 nm.

[0099] (Upper Non-Magnetic Electrode 15)

[0100] The upper non-magnetic electrode (15) is connected to an end face of the second non-magnetic layer (18), which is opposite to the end face in contact with the first recording layer (19). In a specific example, the upper non-magnetic electrode (15) is made of Ta (5 nm). Alternatively, the upper non-magnetic electrode (15) may be made of Ta (5 nm)/Ru (5 nm), Ru (1 to 5 nm), Pt (1 to 5 nm), CoFeB (0.2 to 1.5 nm)/Ta (5 nm) or the like.

[0101] Next, the characteristics of the magnetoresistance effect element of Embodiment 1 of the invention will be explained.

[0102] FIG. 5 shows the thermal stability index E/k.sub.BT calculated with Formula 1 and Formula 2 based on the junction size of MgO/CoFe/CoFeB/CoFe/MgO (total film thickness of the recording layer CoFe/CoFeB/CoFe is 2.6 nm, and 2K.sub.i=3.6 mJ/m2) for the first non-magnetic layer (13)/the first magnetic layer (25)/the second magnetic layer (12)/the third magnetic layer (17)/the second non-magnetic layer (18) in the multilayer structure of FIG. 4. The respective thicknesses of CoFe and CoFeB are set to 0.4 nm and 1.8 nm so that the saturation magnetization Ms of the recording layer is 1 T. By making the thickness ratio of CoFeB/CoFe constant, the saturation magnetization Ms of the overall recording layer can be made constant. In the example described above, the thickness ratio of CoFeB to CoFe is 4.5, and the total thickness of the recording layer is 2.6 nm, but it is also possible to make the total thickness of the recording layer greater than 2.6 nm while keeping the thickness ratio of CoFeB to CoFe of 4.5. As shown in FIG. 5, the MgO/CoFe/CoFeB/CoFe/MgO, in which the recording layer is sandwiched by MgO layers, can achieve a higher E/k.sub.BT than that of Non-patent Document 7 and the calculation result using 2K.sub.i=2.6mJ/m.sup.2, which is expected with the double interface CoFeB/MgO. Furthermore, MgO/CoFe/CoFeB/CoFe/MgO, in which the recording layer is sandwiched between MgO layers, utilizes the interfacial magnetic anisotropy energy density K.sub.i only to raise K.sub.efft, and therefore, by designing the thickness and composition of the intermediate CoFeB part with low saturation magnetization Ms such that it will not cause an increase in damping constant , the writing current I.sub.C0 can be suppressed.

[0103] As described above, the magnetoresistance effect element having the structure of FIG. 4 can achieve high thermal stability while suppressing the writing current I.sub.C0, with a very small element size.

[0104] FIG. 6A and FIG. 6B respectively show the thermal stability index calculated using Formula 1 and Formula 3 for the total thickness t of the recording layer of 20 nm diameter. The demagnetizing field is corrected by ellipsoid approximation.

[0105] FIG. 6A is the thermal stability index when the saturation magnetization Ms of the recording layer is varied from 1.0 to 1.5 T at 2K.sub.i=2.6mJ/m.sup.2, which ideally occurs at the double CoFeB/MgO interface. FIG. 6B is the thermal stability index when the saturation magnetization Ms of the CoFe/CoFeB/CoFe recording layer is varied from 1.0 to 1.5 T at 2K.sub.i=3.6 mJ/m.sup.2 with the double CoFeB/MgO interface. In FIGS. 6A and 6B, as the total film thickness of the recording layer increases, the thermal stability index temporarily decreases due to the decreasing effect of the interface magnetic anisotropy K.sub.i/t. However, when the recording layer thickness exceeds a certain thickness, the thermal stability index starts increasing with the effect of decreasing demagnetizing field ((NzNx) Ms 2/20). If the saturation magnetization Ms is the same, the greater the interfacial magnetic anisotropy energy density K.sub.i is, the higher the thermal stability index is. Also the lower the saturation magnetization Ms of the overall recording layer is, or in other words, the lower the saturation magnetization of the intermediate CoFeB layer of the CoFe/CoFeB/CoFe recording layer is, the higher the thermal stability index is. Therefore, by using the structure in which the CoFe/CoFeB/CoFe recording layer is sandwiched between the MgO layers, the thermal stability index can be improved as compared with the conventional recording layer.

[0106] In FIG. 4, a magnetoresistance effect element having no first magnetic layer or third magnetic layer can likewise obtain high thermal stability while suppressing the writing current I.sub.C0 with a very small element size.

Embodiment 2

[0107] With respect to the first non-magnetic layer (13)/the first magnetic layer (25)/the second magnetic layer (12)/the third magnetic layer (17)/the second non-magnetic layer (18) of the multilayer structure of FIG. 4, the following materials, thicknesses, and B composition were specifically employed: the thickness of CoFeB of the first magnetic layer (25) and the third magnetic layer (17) is 0.4 nm, the thickness of CoFeB of the second magnetic layer (12) is 1.8 nm, the B composition of the first magnetic layer (25) and the third magnetic layer (17) is Co.sub.24Fe.sub.71B.sub.5 (5/100=0.05), the B composition of the second magnetic layer (12) is Co.sub.16Fe.sub.49B.sub.35 (35/100=0.35), and the ratio of the B composition of the first magnetic layer (25) and the third magnetic layer (17) to the B composition of the second magnetic layer (12) is 0.05/0.35=0.14. The ratio of the thickness of CoFeB of the second magnetic layer (12) to the thickness of CoFeB of the first magnetic layer (25) and the third magnetic layer (17) is 4.5, and the total thickness of the recording layer is 2.6 nm. Furthermore, MgO/CoFeB/CoFeB/CoFeB/MgO, in which the recording layer is sandwiched between MgO layers, utilizes the interfacial magnetic anisotropy energy density K.sub.i only to raise K.sub.efft and therefore, by designing the thickness and composition of the intermediate CoFeB part of the first, second, and third magnetic layers, which has low saturation magnetization Ms, such that it will not cause an increase in damping constant , the writing current I.sub.C0 can be suppressed. Also the lower the saturation magnetization Ms of the overall recording layer is, or in other words, the lower the saturation magnetization of the intermediate CoFeB layer of the MgO/CoFeB/CoFeB/CoFeB/MgO is, the higher the thermal stability index is. Therefore, by using the structure in which the CoFeB/CoFeB/CoFeB recording layer is sandwiched between the MgO layers, the thermal stability index can be improved as compared with the conventional recording layer.

[0108] In FIG. 4, a magnetoresistance effect element having no first magnetic layer or third magnetic layer can likewise obtain high thermal stability while suppressing the write current I.sub.C0 with a very small element size.

Embodiment 3

[0109] FIG. 7 shows Embodiment 3 of the magnetoresistance effect element of the invention.

[0110] In Embodiment 3, the second magnetic layer (12) is made of the fourth magnetic layer (12-1) and the fifth magnetic layer (12-2), and the third non-magnetic layer (16) is interposed between the fourth magnetic layer (12-1) and the fifth magnetic layer (12-2) to control the B concentration. The third non-magnetic layer (16) is provided to control the concentration of B.

[0111] In Embodiment 3, the third non-magnetic layer (16) functions as the area to block the diffusion of B from the fourth magnetic layer (12-1) and the fifth magnetic layer (12-2), and has the function of controlling the B concentration in the fourth magnetic layer (12-1) and the fifth magnetic layer (12-2). If the third non-magnetic layer (16) is Ta, for example, it is preferable that the thickness thereof be 1 nm or smaller. As a result, the B concentration of the first magnetic layer (25) and the third magnetic layer (17) is lowered, which allows the interfacial magnetic anisotropy energy density K.sub.i to be high at the interface with the first non-magnetic layer (13) and the second non-magnetic layer (18), and allows areas other than the interface regions to have lower Ms.

[0112] With respect to the first non-magnetic layer (13)/the first magnetic layer (25)/the fourth magnetic layer (12-1)/the third non-magnetic layer (16)/the fifth magnetic layer (12-2)/the third magnetic layer (17)/the second non-magnetic layer (18) of the multilayer structure of FIG. 7, the following materials, thicknesses, and B composition were specifically employed: the thickness of CoFeB of the first magnetic layer (25) and the third magnetic layer (17) is 0.4 nm, the thickness of CoFeB of the fourth magnetic layer (12-1) and the fifth magnetic layer (12-2) is 0.9 nm, the thickness of the third non-magnetic layer (16) is 0.5 nm, the B composition of the first magnetic layer (25) and the third magnetic layer (17) is Co.sub.24Fe.sub.71B.sub.5 (5/100=0.05), and the B composition of the fourth magnetic layer (12-1) and the fifth magnetic layer (12-2) is Co.sub.16Fe.sub.49B.sub.35 (35/100=0.35). The total thickness of the recording layer is 3.1 nm. Furthermore, MgO/CoFeB/CoFeB/Ta/CoFeB/CoFeB/MgO, in which the recording layer is sandwiched between MgO layers, utilizes the interfacial magnetic anisotropy energy density K.sub.i only to raise K.sub.efft, and therefore, by designing the thickness and composition of the intermediate magnetic layer of the first, third, fourth, and fifth magnetic layers with low saturation magnetization Ms, such that it will not cause an increase in damping constant , the writing current I.sub.C0 can be suppressed. Also the lower the saturation magnetization Ms of the overall recording layer is, or in other words, the lower the saturation magnetization of the recording layer CoFeB/CoFeB/Ta/CoFeB/CoFeB of MgO/CoFeB/CoFeB/Ta/CoFeB/CoFeB/MgO is, the higher the thermal stability index is. Therefore, by using the structure in which the CoFeB/CoFeB/Ta/CoFeB/CoFeB recording layer is sandwiched between the MgO layers, the thermal stability index can be improved as compared with the conventional recording layer.

Embodiment 4

[0113] FIG. 8 shows Embodiment 4 of the magnetoresistance effect element of the invention.

[0114] Embodiment 4 differs from Embodiments 1 and 2 in having the second reference layer (32).

[0115] The second reference layer (32) has the function of an anti-parallel coupling reference layer. In the second reference layer (32), the magnetization directions of the respective magnetic layers are opposite to those of the first reference layer 24.

[0116] This is effective to improve the spin injection efficiency and reduce the writing current I.sub.C0.

Embodiment 5

[0117] FIG. 9 shows Embodiment 5 of the magnetoresistance effect element of the invention. Embodiment 5 also has the second reference layer (32) like Embodiment 4, but differs from Embodiment 4 in that the second reference layer is not an antiparallel coupling layer.

Embodiment 6

[0118] FIG. 10 shows Embodiment 6 of the magnetoresistance effect element of the invention. Embodiment 6 has the multilayer structure in which the second magnetic layer (12) and the third magnetic layer (17) are in direct contact as in Embodiments 1 and 2 of the invention, and also includes the second reference layer (32) as in Embodiment 5. Depending on whether it is necessary to control the concentration of B or not, the third non-magnetic layer (16) may be omitted.

Embodiment 7

[0119] FIG. 11 shows Embodiment 7 of the magnetoresistance effect element of the invention. Embodiment 7 has a multilayer structure including two recording layers of the first recording layer (19) and a second recording layer (34), and three reference layers of the first reference layer (24), the second reference layer (32), and the third reference layer (33).

[0120] With Embodiment 7, it is possible to provide the multi-value function using those three reference layers.

Modification Example of Embodiment 1

[0121] Next, the characteristics of the magnetoresistance effect element of a modification example of Embodiment 1 of the invention will be explained.

[0122] The characteristics required for the junction interface between the magnetic layer and the nonmagnetic layer of the perpendicular magnetic anisotropic magnetoresistance effect element applied to the magnetic memory of the invention are the high tunnel magnetoresistance (TMR) ratio, the low writing current I.sub.C0, and high thermal stability. The writing current I.sub.C0 is determined by the damping constant , and it is preferable that the damping constant be 0.01 or smaller, or it is more preferable that the damping constant be 0.005 or smaller. Further, for example, at the junction surface of the magnetoresistance effect element having the junction size diameter of 20 nm, the interfacial magnetic anisotropy energy density K.sub.i is required to be 2.6mJ/m.sup.2 or more.

[0123] In FIG. 4, the first non-magnetic layer (13) and the second non-magnetic layer (18) are made of MgO (1.2 nm), and the third magnetic layer (17) and the first magnetic layer (25) are made of Fe (0.4 nm to 1 nm). The second magnetic layer (12) is made of FeV (0.01 nm to 0.4 nm).

[0124] FIG. 13A shows the interfacial magnetic anisotropy energy density K.sub.i characteristics for the Fe layer thickness when MgO/Fe/FeV/Fe/MgO (junction size diameter of the recording layer Fe/FeV/Fe is 20 nm) were used as the specific materials of the first non-magnetic layer (13)/the first magnetic layer (25)/the second magnetic layer (12)/the third magnetic layer (17)/the second non-magnetic layer (18) in the multilayer structure of FIG. 4. As shown in FIG. 13A, as the Fe layer thickness increases, the interfacial magnetic anisotropy energy density K.sub.i linearly increases.

[0125] FIG. 13B shows the damping constant characteristics for the Fe thickness. As shown in FIG. 13B, as the Fe layer thickness increases, the damping constant slightly increases, but the value thereof stays under 0.005. which is the required value of the damping constant at the junction interface of the junction size diameter 20 nm.

[0126] As described above, the magnetoresistance effect element of the modification example of Embodiment 1 having the structure shown in FIG. 4 can keep the value of the damping constant under a certain level, thereby making it possible to suppress the writing current I.sub.C0 with a very small element size.

[0127] Embodiments 2 to 7 may also be modified in a manner similar to the modification example of Embodiment 1 by applying Fe and FeV to the recording layer.

Modification Example of Embodiment 2

[0128] Next, the characteristics of the magnetoresistance effect element of a modification example of Embodiment 2 of the invention will be explained.

[0129] In FIG. 4, MgO was used for the first non-magnetic layer (13) and the second non-magnetic layer (18), and FeV was used for the third magnetic layer (17) and the first magnetic layer (25). The second magnetic layer (12) is made of FeV having a higher V composition than FeV used for the third magnetic layer (17) and the first magnetic layer (25).

[0130] As the Fe layer thickness increases, the interfacial magnetic anisotropy energy density K.sub.i linearly increases. Also, as the Fe layer thickness increases, the damping constant slightly increases, but the value thereof stays under 0.005. which is the required value of the damping constant at the junction interface of the junction size diameter 20 nm.

[0131] As described above, the magnetoresistance effect element of the modification example of Embodiment 2 having the structure shown in FIG. 4 can keep the value of the damping constant under a certain level, thereby making it possible to suppress the writing current I.sub.C0 even with a very small element size.

[0132] Embodiments 2 to 7 may also be modified in a manner similar to the modification example of Embodiment 2 by applying FeV to the recording layer.

[0133] The respective embodiments and modification examples described above may further modified. For example, by making the ratio of the non-magnetic element composition, such as Ti, Cr, Zr, Nb, Mo, Hf, Ta, W, Si, Al, Pd, and Pt, in the first magnetic layer (25) to the non-magnetic element composition, such as Ti, Cr, Zr, Nb, Mo, Hf, Ta, W, Si, Al, Pd, and Pt, in the second magnetic layer (12) smaller than 1, and by making the ratio of the non-magnetic element composition, such as Ti, Cr, Zr, Nb, Mo, Hf, Ta, W, Si, Al, Pd, and Pt, in the third magnetic layer (17) to the non-magnetic element composition, such as Ti, Cr, Zr, Nb, Mo, Hf, Ta, W, Si, Al, Pd, and Pt, in the second magnetic layer (12) smaller than 1, the value of the damping constant can be kept under a certain level, which makes it possible to suppress the writing current I.sub.C0 even with a very small element size.

[0134] Furthermore, it is also possible to keep the value of the damping constant under a certain level, which makes it possible to suppress the writing current I.sub.CO even with a very small element size, by forming Fe(V) on the CoFe(B) material or laminating different non-magnetic elements or different magnetic elements. Specific examples of the multilayer structure include MgO/FeB/FeV/FeB/MgO, MgO/Fe.sub.95B.sub.5/FeV/Fe.sub.90B.sub.10/MgO, MgO/Co.sub.24Fe.sub.71B.sub.5/FeV/Co.sub.22Fe.sub.68B.sub.10/MgO, MgO/Co.sub.47Fe.sub.48B.sub.5/FeV/Co.sub.22Fe.sub.68B.sub.10/MgO, MgO/FeB/FeV/FeTa/MgO, and MgO/(Co)FeB/FeV/(Co)FeM/MgO (M includes at least Ti, Cr, Zr, Nb, Mo, Hf, Ta, W, Si, Al, Pd, and Pt, and two or more types of elements may be mixed).

Magnetic Memory 1 in Embodiment of the Invention

[0135] FIG. 12 shows a magnetic memory (MRAM) as an embodiment of the invention.

[0136] As shown in FIG. 12, the magnetic memory (1) includes a plurality of source lines (2), a plurality of word lines 3, a plurality of bit lines (4), and a plurality of memory cells (5).

[0137] The respective source lines (2) are arranged in parallel with each other. The respective word lines (3) are arranged in parallel with each other in the direction intersecting with the source lines (2). The respective bit lines (4) are arranged in parallel with each other so as to be in parallel with the respective source lines (2). The respective source lines (2) and the respective bit lines (4) are alternately arranged in parallel with each other in the lateral direction. One end of each source line (2) and each bit line (4) is electrically connected to a write driver (6) and a sense amplifier (7) for voltage application. One end of each word line (3) is electrically connected to a word driver (8).

[0138] Each memory cell (5) is disposed at each intersection of the bit lines (4) and the word lines (3). Each memory cell (5) includes a select transistor (9) and a magnetoresistance effect element (10). In the select transistor (9), the gate electrode is electrically connected to the word line (3), and the source electrode is electrically connected to the source line (2) via a wiring layer. In the magnetoresistance effect element (10), one of the sixth magnetic layer (11) and the second magnetic layer (12) is electrically connected to the drain electrode of the select transistor (9) via a lower non-magnetic electrode (14) or an upper non-magnetic electrode (15), and the other is electrically connected to the bit line (4). The magnetoresistance effect element (10) is one of those shown in FIG. 1, 4, or 6 to 11. The magnetic memory (1) is configured so as to be able to apply a current to the magnetoresistance effect element (10) along the thickness direction.

[0139] Next, the operation will be explained.

[0140] In an operation to write 1, the write driver (6) applies a voltage on the source lines (2), and the word driver (8) applies a voltage on the word lines (3), thereby causing a current to flow from the source line (2) to the bit line (4) via the magnetoresistance effect element (10). This makes the magnetization direction of the second magnetic layer (12), which is the recording layer of the magnetoresistance effect element (10) having a free magnetization direction, antiparallel to the magnetization direction of the sixth magnetic layer (11), which is the reference layer having a fixed magnetization direction. As a result, the magnetoresistance effect element (10) enters a high resistance state, and the magnetoresistance effect element (10) holds the information 1.

[0141] On the other hand, in an operation to write 0, the write driver (6) applies a voltage on the bit line (4), and the word driver (8) applies a voltage on the word lines (3), thereby causing a current to flow from the bit line (4) to the source line (2) via the magnetoresistance effect element (10). This makes the magnetization direction of the second magnetic layer (12), which is the recording layer of the magnetoresistance effect element (10) having a free magnetization direction, parallel to the magnetization direction of the sixth magnetic layer (11), which is the reference layer having a fixed magnetization direction. As a result, the magnetoresistance effect element (10) enters a low resistance state, and the magnetoresistance effect element (10) holds the information 0.

[0142] In order to read out the information, the sense amplifier (7) reads out a difference in signals due to the change in resistance. By such a memory array, it is possible to achieve a magnetic memory having the magnetoresistance effect element 10 with a larger magnetoresistance change rate, a smaller write current, and a higher thermal stability than that of the conventional structure.