VOLTAGE-CONTROLLED THREE-TERMINAL MAGNON TRANSISTOR, AND CONTROL AND PREPARATION METHOD THEREOF

Abstract

A voltage-controlled three-terminal magnon transistor is provided, including a ferroelectric layer, a magnetic layer, a generation terminal, a control terminal, a detection terminal, and a bottom electrode. After a current is inputted into the generation terminal, a magnon is generated in the magnetic layer. The detection terminal is made of a heavy metal material, which can convert the magnon in the magnetic layer into a charge flow. When a voltage pulse applied between the control terminal and the bottom electrode exceeds a critical value, non-volatile polarization and non-volatile strain states of the ferroelectric layer change, which in turn affects a transmission capability of the magnon in the magnetic layer based on a magnetoelectric coupling effect between the ferroelectric layer and the magnetic layer. In addition, a voltage signal of the detection terminal exhibits a regular loop change behavior with a change of the voltage pulse.

Claims

1. (canceled)

2. A voltage-controlled three-terminal magnon transistor, comprising: a ferroelectric layer; a magnetic layer formed on a first surface of the ferroelectric layer; a generation terminal, a control terminal, and a detection terminal, wherein the generation terminal, the control terminal, and the detection terminal are formed on the magnetic layer, and the detection terminal is made of a heavy metal material; and a bottom electrode formed on a second surface of the ferroelectric layer, wherein the second surface is arranged opposite to the first surface; wherein the generation terminal is further configured to generate a magnon in the magnetic layer based on a thermal effect after a current is inputted; the detection terminal is further configured to convert the magnon in the magnetic layer into a charge flow based on a strong spin-orbit coupling effect of the detection terminal; the ferroelectric layer is further configured to change non-volatile polarization and non-volatile strain states of the ferroelectric layer when a voltage pulse applied between the control terminal and the bottom electrode exceeds a critical value, and further affect a transmission capability of the magnon in the magnetic layer based on a magnetoelectric coupling effect between the ferroelectric layer and the magnetic layer; and the detection terminal is further configured to enable a detected voltage signal to exhibit a regular loop change behavior with a change of the voltage pulse.

3. The voltage-controlled three-terminal magnon transistor according to claim 2, wherein the generation terminal is made of the heavy metal material.

4. The voltage-controlled three-terminal magnon transistor according to claim 3, wherein the heavy metal material is one of platinum, gold, palladium, tungsten, and tantalum.

5. The voltage-controlled three-terminal magnon transistor according to claim 3, wherein the generation terminal is further configured to generate a spin current based on a strong spin-orbit coupling effect after a current is inputted; and the spin current is converted into a magnon after being injected into the magnetic layer.

6. The voltage-controlled three-terminal magnon transistor according to claim 3, wherein the control terminal is made of the heavy metal material.

7. The voltage-controlled three-terminal magnon transistor according to claim 2, wherein the ferroelectric layer is a ferroelectric substrate, a ferroelectric film, or a ferroelectric slice; and the ferroelectric layer is made of any one of lead magnesium niobate-lead titanate, lead zirconate titanate, barium titanate, potassium dihydrogen phosphate, lead titanate, and lead tungstate.

8. The voltage-controlled three-terminal magnon transistor according to claim 7, wherein the ferroelectric layer is the ferroelectric film or the ferroelectric slice with a thickness of 1 nanometer to 2 millimeters.

9. The voltage-controlled three-terminal magnon transistor according to claim 7, wherein the ferroelectric layer is made of the lead magnesium niobate-lead titanate.

10. The voltage-controlled three-terminal magnon transistor according to claim 2, wherein the magnetic layer is made of a magnetic insulator material, and the magnetic insulator material comprises yttrium iron garnet ferrite, iron trioxide, and chromic oxide.

11. The voltage-controlled three-terminal magnon transistor according to claim 10, wherein the magnetic layer is made of the yttrium iron garnet ferrite.

12. The voltage-controlled three-terminal magnon transistor according to claim 10, wherein a thickness of the magnetic layer ranges from 1 nanometer to 100 micrometers, and is preferably 10050 nanometers.

13. The voltage-controlled three-terminal magnon transistor according to claim 10, wherein a thickness of the magnetic layer is 10050 nanometers.

14. The voltage-controlled three-terminal magnon transistor according to claim 2, wherein the bottom electrode is located directly below the control terminal and wraps the control terminal, and the bottom electrode is made of a conductive material.

15. The voltage-controlled three-terminal magnon transistor according to claim 14, wherein the conductive material comprises at least one of platinum, gold, palladium, tungsten, tantalum, silver, copper, aluminum, titanium, silicon, gallium arsenide, gallium nitride, and titanium dioxide.

16. A control method of a three-terminal magnon transistor, wherein the control method is based on a voltage-controlled three-terminal magnon transistor, the voltage-controlled three-terminal magnon transistor comprises: a ferroelectric layer; a magnetic layer formed on a first surface of the ferroelectric layer; a generation terminal, a control terminal, and a detection terminal, wherein the generation terminal, the control terminal, and the detection terminal are formed on the magnetic layer, and the detection terminal is made of a heavy metal material; and a bottom electrode formed on a second surface of the ferroelectric layer, wherein the second surface is arranged opposite to the first surface; the control method comprises: inputting a direct current or a low-frequency alternating current into the generation terminal; and applying a voltage pulse V.sub.g from V.sub.g1 to V.sub.g1 between the control terminal and the bottom electrode, wherein when the voltage pulse V.sub.g is greater than a positive critical value V.sub.t, a transmission capability of a magnon in a magnetic insulation layer is strengthened, and a voltage signal V of the detection terminal increases; and applying a voltage pulse V.sub.g from the V.sub.g1 to the V.sub.g1 between the control terminal and the bottom electrode, wherein when the voltage pulse V.sub.g is less than a negative critical value V.sub.t, the transmission capability of the magnon is weakened, and the voltage signal V of the detection terminal decreases, such that the voltage signal of the detection terminal exhibits a regular loop change behavior with a change of the voltage pulse.

17. A preparation method, wherein the preparation method is used to prepare the voltage-controlled three-terminal magnon transistor according to claim 2, and comprises: providing a ferroelectric substrate or making a ferroelectric film as the ferroelectric layer; growing a magnetic layer film on the first surface of the ferroelectric layer by using a film growth technology; making a sequentially side-by-side arranged generation terminal, control terminal, and detection terminal on the magnetic insulator layer film by using an ultra-violet lithography, electron beam exposure, or etching technology and a coating technology; and finally growing the bottom electrode on the second surface of the ferroelectric layer.

18. The voltage-controlled three-terminal magnon transistor according to claim 3, wherein the ferroelectric layer is a ferroelectric substrate, a ferroelectric film, or a ferroelectric slice; and the ferroelectric layer is made of any one of lead magnesium niobate-lead titanate, lead zirconate titanate, barium titanate, potassium dihydrogen phosphate, lead titanate, and lead tungstate.

19. The voltage-controlled three-terminal magnon transistor according to claim 4, wherein the ferroelectric layer is a ferroelectric substrate, a ferroelectric film, or a ferroelectric slice; and the ferroelectric layer is made of any one of lead magnesium niobate-lead titanate, lead zirconate titanate, barium titanate, potassium dihydrogen phosphate, lead titanate, and lead tungstate.

20. The voltage-controlled three-terminal magnon transistor according to claim 5, wherein the ferroelectric layer is a ferroelectric substrate, a ferroelectric film, or a ferroelectric slice; and the ferroelectric layer is made of any one of lead magnesium niobate-lead titanate, lead zirconate titanate, barium titanate, potassium dihydrogen phosphate, lead titanate, and lead tungstate.

21. The voltage-controlled three-terminal magnon transistor according to claim 6, wherein the ferroelectric layer is a ferroelectric substrate, a ferroelectric film, or a ferroelectric slice; and the ferroelectric layer is made of any one of lead magnesium niobate-lead titanate, lead zirconate titanate, barium titanate, potassium dihydrogen phosphate, lead titanate, and lead tungstate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIGS. 1A-1B are a schematic structural diagram of a three-terminal magnon transistor in the prior art, where FIG. 1A is a top view, FIG. 1B is a cross-sectional view, and reference numerals in FIGS. 1A-1B are as follows: 1: magnon generation terminal (S); 2: magnon control terminal (G); 3: magnon detection terminal (D); and 4: magnon transmission medium;

[0023] FIG. 2 is a schematic structural diagram of a three-terminal magnon transistor according to an embodiment;

[0024] FIG. 3 is a schematic flowchart of preparing a three-terminal magnon transistor according to an embodiment;

[0025] FIGS. 4A-4B are a schematic diagram of working of a three-terminal magnon transistor according to an embodiment, where FIG. 4A is a top view, and FIG. 4B is a side view;

[0026] FIG. 5 is a schematic diagram of a curve indicating that a voltage signal detected by a three-terminal magnon transistor changes with a voltage pulse according to an embodiment; and

[0027] FIG. 6 shows experimental data of a curve indicating that a voltage signal detected by a three-terminal magnon transistor changes with a voltage pulse according to an embodiment.

[0028] Reference numerals in FIG. 2, FIG. 3, and FIGS. 4A-4B: 1: ferroelectric layer; 2: magnetic layer; 3: generation terminal; 4: control terminal; 5: detection terminal, 6: bottom electrode; 7: current source for applying a current; 8: voltmeter for detecting a voltage signal; and 9: voltage source for applying a voltage pulse.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The technical solutions of the present disclosure are described clearly and completely below with reference to specific embodiments and FIG. 2 to FIG. 6. Apparently, the described embodiments are merely a part rather than all of the embodiments of the present disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of the present disclosure without creative efforts shall fall within the protection scope of the present disclosure.

[0030] As shown in FIG. 2, Embodiment 1 provides a voltage-controlled three-terminal magnon transistor, which is mainly constituted by ferroelectric layer 1, magnetic layer 2, generation terminal 3, control terminal 4, detection terminal 5, and bottom electrode 6. The ferroelectric layer 1 is a ferroelectric substrate, a ferroelectric film, or a ferroelectric slice. Polarization and strain states of the ferroelectric layer can be changed by applying a voltage, and transmission efficiency of a magnon in the magnetic insulator layer can be regulated based on a magnetoelectric coupling effect of a ferroelectric/ferromagnetic system. Materials available for the ferroelectric layer 1 include lead magnesium niobate-lead titanate (PMN.sub.x-PT.sub.1-x), lead zirconate titanate (PZT), barium titanate (BaTiO.sub.3), potassium dihydrogen phosphate (KH.sub.2PO.sub.4), lead titanate (PbTiO.sub.3), lead tungstate (PbZrO.sub.3), and the like. The lead magnesium niobate-lead titanate is preferred, which has a wide temperature range, a strong piezoelectric effect, and a mature preparation technology. This device is not sensitive to a thickness of the ferroelectric layer 1. A millimeter-thick ferroelectric substrate may be directly purchased through commercial means, or the ferroelectric film or the ferroelectric slice with a thickness of 1 nanometer to 2 millimeters may be grown on a suitable substrate (such as a silicon slice). Compared with the ferroelectric substrate, the ferroelectric film requires only a smaller voltage to be applied to achieve same electric field strength.

[0031] The magnetic layer 2 is a magnon transmission medium. The magnon transmission medium can be obtained by growing a magnetic film on the ferroelectric layer 1 by using a film growth device. Specifically, a magnetic material with a magnetic ordering temperature higher than a room temperature, a small damping coefficient, and a long magnon transmission distance can be selected to prepare the magnetic film. Considering that a damping factor of a magnetic insulator is generally less than that of magnetic metal, and a transmission distance of the magnon is also generally greater than that of the magnetic metal, a magnetic insulator material is preferably selected to prepare the magnetic layer 2, such as yttrium iron garnet ferrite (Y.sub.3Fe.sub.5O.sub.12, abbreviated as YIG), iron trioxide (Fe.sub.2O.sub.3), or chromic oxide (Cr.sub.2O.sub.3). The YIG is a preferred material among the magnetic insulators, which has advantages such as a mature preparation technology, a wide temperature range, a very small damping factor, and a long magnon transmission distance. A thickness of a magnetic insulator layer film usually ranges from 1 nanometer to 100 micrometers, and is preferably 10050 nanometers. Within this range, properties of the magnetic film are close to those of a bulk material, with a small damping coefficient, a long magnon transmission distance, and a less attenuation of the magnetoelectric coupling effect.

[0032] The generation terminal 3, the control terminal 4, and the detection terminal 5 are all micro strips formed on a surface of the magnetic layer 2. The generation terminal 3 and the control terminal 4 are made of a conductive material such as a metallic conductive material like platinum, gold, palladium, tungsten, tantalum, silver, copper, aluminum, titanium, or titanium dioxide, or a non-metallic conductive material like silicon, gallium arsenide, or gallium nitride. After a current is inputted into the generation terminal 3, the magnon is generated in the magnetic layer 2 based on a thermal effect (for example, a spin Seebeck effect). The detection terminal 5 is made of a heavy metal material such as platinum, gold, palladium, tungsten, or tantalum, and is configured to detect the magnon. Preferably, the generation terminal 3 is made of heavy metal. In this way, the magnon can be generated in the magnetic layer 2 based on the thermal effect caused by heating, and a spin current can be generated based on a strong spin-orbit coupling effect of the generation terminal 3 and is converted into the magnon in the magnetic layer 2. Further, for simplicity of process implementation, the generation terminal 3, the control terminal 4, and the detection terminal 5 may be made of a same heavy metal material, such that exposure and coating need to be performed only once. A size and a spacing of the three micro strips can be designed conventionally, for example, with a strip length of 10 microns, a width of 0.5 microns, and a strip spacing of 0.5 microns. In a practical application, the size and the spacing of the micro strips can be further reduced as needed, without a need to follow a same proportion as the above example.

[0033] The bottom electrode 6 is formed on a surface of the ferroelectric layer 1 opposite to the magnetic layer 2. As an electrode for applying the voltage, the bottom electrode 6 is made of the conductive material such as conductive metal like platinum, gold, palladium, tungsten, tantalum, silver, copper, aluminum, or titanium, or a semiconductor material like silicon, gallium arsenide, gallium nitride, or titanium dioxide. The bottom electrode 6 is preferably located directly below the control terminal 4, and its size is similar to a size of the control terminal 4. Preferably, the bottom electrode 6 is arranged directly corresponding to the control terminal 4 and can cover the control terminal 4.

[0034] A working principle of the three-terminal magnon transistor described in Embodiment 1 is as follows: As shown in FIG. 4A, direct current (or low-frequency alternating current) I is inputted into the generation terminal 3 by using current source 7. The generation terminal 3 is made of the conductive material, and can inject the spin current into the magnetic layer 2 through two ways: 1) The current in the generation terminal 3 heats the magnetic layer 2, a temperature gradient is established, and the magnon is generated in the magnetic layer based on the thermal effect. A polarization direction of the magnon can be adjusted by in-plane magnetic field .sub.0H. 2) If the generation terminal 3 is made of the heavy metal material, its strong spin-orbit coupling effect can also be used to enable a charge flow to directly generate the spin current, and the spin current is converted into the magnon in the magnetic layer 2. The polarization direction of the magnon is controlled by a direction of the charge flow in the generation terminal 3. The magnon is transmitted towards the right in the magnetic layer 2 and reaches the detection terminal 5. The detection terminal 5 made of the heavy metal material utilizes its strong spin-orbit coupling effect to convert the magnon into the charge flow, and voltage signal V of the detection terminal 5 can be obtained by using voltmeter 8 (or a lock-in amplifier).

[0035] As shown in FIG. 4B, based on the three-terminal magnon transistor shown in FIG. 4A, when electric field strength generated by the applied voltage in the ferroelectric layer exceeds a critical value, non-volatile polarization and non-volatile strain states of the ferroelectric layer change. The critical electric field strength is an intrinsic property of a ferroelectric material, and its numerical value mainly depends on a selected material. An electric field is equal to the voltage divided by a distance between the control terminal 4 and the bottom electrode 6. Therefore, a critical value of the voltage is also related to thicknesses of the ferroelectric layer and a magnetic transmission layer. For a same device, due to a fixed material and thickness, voltage strength is linearly related to the voltage. That is, voltage pulse V.sub.g is applied between the control terminal 4 and the bottom electrode 6. When the V.sub.g exceeds a critical voltage (in other words, an absolute value is greater than an absolute value of the critical voltage), the polarization and strain states of ferroelectric layer 1 change, and then a magnetoelectric coupling effect between the ferroelectric layer 1 and the magnetic layer 2 affects a transmission capability of the magnon in the magnetic layer 2. Due to a non-volatile nature of polarization and strain changes in the ferroelectric layer 1, the polarization and strain states of the ferroelectric layer 1 are maintained even after the applied voltage pulse is removed, thereby achieving non-volatile regulation for the transmission capability of the magnon in the magnetic layer 2.

[0036] Specifically, a voltage pulse from V.sub.g1 to V.sub.g1 is applied between the control terminal 4 and the bottom electrode 6. A width of the voltage pulse can be selected from 1 nanosecond to 10 seconds, and a pulse waveform is not limited and may be stepped, diagonal, stair-stepped, or the like. When the voltage is greater than positive critical value V.sub.t, polarization and strain in the ferroelectric layer 1 change, and the transmission capability of the magnon in the magnetic layer 2 increases based on the magnetoelectric coupling effect. In an experiment, it is observed that the voltage signal V of the detection terminal 5 increases. A voltage pulse from V.sub.g1 to V.sub.g1 is applied. When the voltage is less than negative critical value V.sub.t, the polarization and the strain in the ferroelectric layer 1 change, and the transmission capability of the magnon in the magnetic layer 2 decreases based on the magnetoelectric coupling effect. In the experiment, it is observed that the voltage signal V of the detection terminal 5 decreases. In summary, the voltage signal V of the detection terminal 5 exhibits a regular loop change behavior with a change of the voltage pulse V.sub.g, in other words, there is a dependence relationship between the V and V.sub.g, as shown in FIG. 5.

[0037] As shown in FIG. 6, in an embodiment, different voltage pulses ranging from 200 V to 200 V and then to 200 V can be applied to the lead magnesium niobate-lead titanate (ferroelectric layer 1) with a thickness of 0.5 millimeters and the yttrium iron garnet ferrite (magnetic layer 2) with a thickness of 100 nanometers. The width of the voltage pulse is 10 seconds, and the pulse waveform is diagonal. An actually measured voltage signal of the detection terminal 5 is obtained. It can be seen that the voltage signal V measured for the detection terminal 5 undergoes a significant change at 150 V and 100 V, corresponding to changes in the polarization and strain states of the lead magnesium niobate-lead titanate, thereby affecting the transmission capability of the magnon in the yttrium iron garnet ferrite.

[0038] As shown in FIG. 3, Embodiment 2 provides a preparation method of a device. The preparation method is used to prepare the three-terminal magnon transistor described in Embodiment 1. The preparation method mainly includes following steps. [0039] Step 1: A commercially purchased single crystal substrate made of lead magnesium niobate-lead titanate and with a thickness of 0.5 millimeters is used as a carrier of the device, and thus ferroelectric layer 1 is obtained. [0040] Step 2. A magnetic layer film is grown on a front face of the ferroelectric layer 1 by using a film growth technology, for example, yttrium iron garnet ferrite with a thickness of 100 nanometers is grown. [0041] Step 3: Three nanometer-thick metal strips are made on the magnetic layer film by using an ultra-violet lithography, electron beam exposure, or etching technology and a coating technology, for example, platinum with a length of 10 microns, a width of 0.5 microns, a strip spacing of 0.5 microns, and a thickness of 5 nanometers. [0042] Step 4: On a back face of the ferroelectric layer 1, bottom electrode 6 is grown at a position facing control terminal 4. For example, gold with a thickness of 100 nanometers is used as the bottom electrode 6. Up to now, a target three-terminal magnon transistor is formed.

[0043] Finally, it should be noted that although embodiments of the present disclosure have been presented and described as much as possible, those skilled in the art can still make modifications and improvements to the present disclosure based on the aforementioned embodiments, which should be included in the protection scope of the present disclosure.