A method for realizing a voltage-controlled storage unit based on tunnel magnetoresistance

Abstract

The present invention discloses a method for implementing a voltage-controlled memory cell based on tunnel magnetoresistance (TMR), which relates to the field of magnetic storage technology. A pair of in-plane electrodes are designed on the upper surface of a piezoelectric telescopic layer, i.e., in the same plane as the tunnel junction, and a bottom electrode is formed on the lower surface of a substrate. A voltage is applied perpendicularly to the piezoelectric telescopic layer using the single in-plane electrode and the bottom electrode. This inverse magnetoelectric coupling effect allows the magnetic moment of the free layer of the tunnel junction to rotate within 90° of its initial orientation. Furthermore, positive and negative voltages are applied using a pair of in-plane electrodes to introduce local strain, causing the magnetic moment to rotate in directions 45° and 135° from the initial orientation, respectively, thereby assisting the magnetic moment in overcoming the 90° reversal barrier. Thus, applying voltage in a regular pattern allows for reversible and repeatable 180° reversal of the magnetic moment, resulting in modulation of the parallel and antiparallel states between the free and pinned layers, achieving maximum tunnel magnetoresistance control and facilitating the development of low-power, voltage-controlled magnetic memory devices.

Description

Technical Field

[0001] The present invention relates to the field of magnetic storage technology, and more particularly to the field of a method for implementing a voltage-controlled storage unit based on tunnel magnetoresistance. Background Art

[0002] Magnetic storage technology is based on thin-film magnetic memory cells. By appropriately modulating the same memory cell to produce two distinct magnetoresistance states, high and low, this effect can be exploited to store the information "1" and "0." The phenomenon in which the magnetoresistance of a thin film exhibits high and low magnetoresistance states in response to an external magnetic field is known as the magnetoresistance effect. Common magnetoresistance effects include anisotropic magnetoresistance, giant magnetoresistance, and tunnel magnetoresistance, and various magnetic storage technologies have been exploited to achieve these goals.

[0003] Among them, magnetic random access memories (RAMs) based on tunnel magnetoresistance (TMR) offer advantages such as high density, fast read / write speeds, and non-volatility, making them the most promising memory devices. The basic structure of a magnetic tunnel junction is a free layer / oxide barrier layer / pinned layer. In this structure, the free layer is a thin magnetic film with a small coercive field. The orientation of the free layer's magnetic moment can be manipulated by varying the external field. The pinned layer can be made of a magnetic material with a large coercive field or a ferromagnetic / antiferromagnetic exchange bilayer, ensuring that the magnetic moment in the pinned layer is not modulated by the external field during storage.

[0004] This allows for parallel and antiparallel orientation states between the free layer and the pinned layer, respectively. Based on the tunnel magnetoresistance effect, the tunnel junction can achieve low and high resistance states, respectively, thereby enabling information storage. Currently, information writing in magnetic random access memory utilizes a magnetic field or spin current generated by an electric current to modulate the magnetic moment orientation. Technologies using a magnetic field generated by an electric current to achieve writing face challenges such as high power consumption and difficulty achieving high density. Methods using spin currents passing through the tunnel junction face reduced write life due to heat generation caused by the large write current passing through the tunnel junction. These factors hinder the development of these magnetic storage chip devices.

[0005] To address this issue, voltage can be used instead of current to control the orientation of the free layer of the memory cell, enabling data to be written into the tunnel junction. This approach can effectively reduce power consumption during data writing and has broad application prospects. Currently, the simplest method for achieving electric-field-controlled magnetic moment reversal is magnetoelectric coupling, based on a magnetoelectric heterojunction. However, due to the magnetoelastic coupling mechanism, the rotation angle of the ferromagnetic layer's magnetic moment regulated by an electric field is limited to within 90°. Many patents currently based on this effect (such as Taiwan Patent TWI665667B and Chinese Invention Patent CN110137344A) can only achieve magnetic moment reversals within 90°. For a magnetic tunnel junction, modulating the parallel and antiparallel states of the two ferromagnetic layers requires a 180° magnetization reversal of the free layer. Therefore, currently, an external auxiliary magnetic field or spin current is required to achieve a 180° reversal of the magnetic moment based on the magnetoelectric coupling effect. However, the introduction of these auxiliary fields will still bring about certain energy consumption. If the magnetoelectric coupling mechanism can be fully applied to achieve full voltage mode regulation of the 180° flipping of the magnetic moment of the magnetic layer, it will further promote the ultra-low energy consumption development of tunnel junction magnetic storage units and meet application needs.

[0006] Therefore, the present invention is to solve this problem. Summary of the Invention

[0007] The purpose of the present invention is to solve the above technical problems and provide a method for realizing a voltage-controlled storage unit based on tunnel magnetoresistance.

[0008] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0009] A method for implementing a voltage-controlled storage unit based on tunnel magnetoresistance comprises the following steps:

[0010] Step 1: Select a piezoelectric telescopic layer for piezoelectric electromagnetic storage, wherein the piezoelectric telescopic layer can generate negative strain in the crystal axis direction of the piezoelectric telescopic layer when a voltage is applied to its upper and lower surfaces, whether it is a positive voltage or a negative voltage, and the

[001] crystal axis direction is set to the x direction;

[0011] Step 2: A magnetic tunnel junction film is formed on the upper surface of the piezoelectric stretching layer, and a buffer layer, a free layer, an oxide barrier layer, a pinned layer, and an antiferromagnetic layer are sequentially formed on the piezoelectric stretching layer. When a voltage is applied, the magnetic moment of the free layer rotates according to the magnetoelastic coupling energy due to the magnetoelectric coupling effect, while the magnetic moment of the pinned layer is substantially unaffected.

[0012] Step 3: Prepare a pair of electrodes D1 and D2 on the top surface of the piezoelectric stretchable layer. The two electrodes are of equal size, parallel to each other, and located on either side of the tunnel junction. The center line of the two electrodes is in the x' direction, 45° offset from the x-axis in the plane. The direction perpendicular to the x' direction is the y' direction, 135° offset from the x-axis.

[0013] At the same time, another electrode D3 is prepared on the surface of the electrode plate under the piezoelectric stretch layer. The electrode material can be Cu, Ag, or Au. The electrode plate and electrode material should be selected based on good conductivity and low shear strength to minimize the impact on the performance of the piezoelectric stretch layer.

[0014] Step 4: When the magnetostriction coefficient of the free layer magnetic material used for tunnel junction preparation is positive, in the initial state, the initial magnetic moment of the free layer magnetic film is set in the positive direction of the x-axis. By applying a voltage to the pair of electrodes D1 and D3, the initial magnetic moment of the free layer can be turned to the y-axis direction due to the inverse magnetoelectric coupling effect. Applying positive and negative voltages to the pair of electrodes D1 and D2 can make the initial magnetic moment of the free layer turn to the x' and y' directions respectively.

[0015] When the magnetostriction coefficient of the free layer magnetic material used for tunnel junction preparation is negative, in the initial state, the initial magnetic moment of the free layer magnetic film is set in the positive direction of the y-axis. By applying voltage to the pair of electrodes D1 and D3, the initial magnetic moment of the free layer can be turned to the x-axis direction due to the inverse magnetoelectric coupling effect. Applying positive and negative voltages to the pair of electrodes D1 and D2 can make the initial magnetic moment of the free layer turn to the y' and x' directions respectively.

[0016] As an optional technical solution, in step 1, the piezoelectric material used in the piezoelectric telescopic layer includes but is not limited to PMN-PT and PZN-PT.

[0017] As an optional technical solution, a vacuum coating process is used to deposit Au at an appropriate position on the surface of the lower electrode plate of the piezoelectric telescopic layer, which serves as the bottom electrode D3 for applying a voltage to the piezoelectric telescopic layer. When a voltage is applied to the piezoelectric telescopic layer, the strain generated by the piezoelectric telescopic layer is volatile.

[0018] As an optional technical solution, in step 2, an induced magnetic field H may be applied during the film preparation process to set the easy magnetization axis direction of the free layer, and the easy axis of the free layer is set along the x-axis direction.

[0019] As an optional technical solution, in step 3, a standard lift-off photolithography process is used to prepare the in-plane electrodes D1 and D2. The centerline direction of the two electrodes is 45° away from the x-axis in the plane, which is set as the x' direction. The y' direction is perpendicular to the x' direction and is 135° away from the x-axis in the plane.

[0020] Au is prepared as the electrode film using magnetron sputtering equipment, and the photoresist is removed using acetone or a cleaning solution after the film is sputtered.

[0021] As an optional technical solution, the free layer and the fixed layer are magnetic materials. Optional materials include but are not limited to CoFe, Co, CoFeB, and NiFe. The coercive field of the free layer should be smaller than that of the fixed layer, and the free layer should be made of a magnetic material with large magnetostriction to ensure the response of magnetoelectric coupling.

[0022] As an optional technical solution, when the initial magnetic moment of the free layer magnetic film is set in the positive direction of the x-axis; when a positive voltage is applied to the pair of electrodes D1 and D2 on the piezoelectric stretching layer, switches K1 and K2 are closed; the negative electrode is connected to D3, and a local positive strain is generated in the region between the pair of electrodes D1 and D2, causing the magnetic moment to deviate from the x-axis direction and align in the x' direction of the line connecting the centers of the two electrodes, that is, deviate 45 degrees from the x-axis direction; then the connection of electrode D2 is disconnected, switch K2 is opened, and a positive voltage is applied to the electrodes D1 and D3. Due to the piezoelectric effect of the selected piezoelectric stretching layer, a negative strain is generated along the crystal axis of the piezoelectric stretching layer. Through the inverse magnetoelectric coupling effect, the magnetic moment of the free layer is affected by this strain and deflected in the y direction, that is, deviated 90 degrees from the x-axis.

[0023] Then, a negative voltage is applied to the pair of electrodes D1 and D2, and switches K1 and K2 are closed, with the positive electrode connected to D3. At this time, local negative strain will be generated in the area between the pair of electrodes D1 and D2, causing the magnetic moment to turn to the y' direction perpendicular to the center line of the D1 and D2 electrodes, that is, deviate 135° from the x-axis; then the connection between electrodes D1 and D2 is disconnected, and the voltage is removed. At this time, the free layer magnetic moment will return to the negative direction of the initial easy magnetization axis, that is, the 180° direction, thereby realizing the reversal of the free layer magnetic moment from 0° to 180°.

[0024] As an optional technical solution, when achieving a 180° to 0° flip of the free layer magnetic moment, first apply a positive voltage to electrodes D1 and D2, and connect the negative electrode to D3. At this time, the local positive strain between the electrodes D1 and D2 causes the magnetic moment to deviate from the negative direction of the x-axis and align in the x' direction, the line connecting the centers of the two electrodes, that is, in the 225° direction. Then, disconnect the electrode D2, and apply a positive voltage to the electrodes D1 and D3. At this time, negative strain is generated in the x-direction, and the free layer magnetic moment will turn to the y-axis direction, that is, in the 270° direction.

[0025] A negative voltage is then applied to the pair of electrodes D1 and D2, with the positive electrode connected to D3. The localized negative strain between the pair of electrodes D1 and D2 causes the magnetic moment to shift in the y' direction, or 315°. The connection between electrodes D1 and D2 is then disconnected, and the voltage is removed. The free layer magnetic moment returns to the positive direction of the initial easy magnetization axis, or 360° or 0°. This achieves a reversible and repeatable 180° flip of the free layer magnetic moment.

[0026] As an optional technical solution, when the initial magnetic moment of the free layer magnetic film is set in the positive direction of the y-axis, that is, in the 90° direction in the plane; when a positive voltage is applied to the pair of electrodes D1 and D2 on the substrate, and the negative electrode is connected to D3, a local positive strain will be generated in the area between the pair of electrodes D1 and D2, causing the magnetic moment to deviate from the y-axis direction and align in the y' direction perpendicular to the line connecting the center of the electrodes, that is, in the 135° direction; then the connection of electrode D2 is disconnected, and a positive voltage is applied to the electrodes D1 and D3. At this time, a negative strain is generated along the crystal axis of the piezoelectric stretching layer. Through the inverse magnetoelectric coupling effect, the magnetic moment of the free layer will be affected by this strain and deflected to the x direction, that is, in the 180° direction.

[0027] Then, a negative voltage is applied to the pair of electrodes D1 and D2, and the positive electrode is connected to D3. At this time, local negative strain will be generated in the area between the pair of electrodes D1 and D2, causing the magnetic moment to turn to the x' direction of the electrode center line, that is, the 225° direction; then the connection between electrodes D1 and D2 is disconnected, and the voltage is removed. At this time, the free layer magnetic moment will return to the negative direction of the initial easy magnetization axis, that is, the 270° direction, thereby realizing a 180° reversal of the free layer magnetic moment.

[0028] As an optional technical solution, a positive voltage is applied to electrodes D1 and D2, and the negative electrode is connected to D3. At this time, the local positive strain between the electrodes D1 and D2 causes the magnetic moment to deviate from the negative direction of the y-axis and align in the y' direction, that is, the 315° direction. Then, the connection of electrode D2 is disconnected, and a positive voltage is applied to the electrodes D1 and D3. At this time, a negative strain is generated in the x-direction, and the magnetic moment of the free layer will turn to the x-axis direction, that is, the 0° direction.

[0029] A negative voltage is then applied to the pair of electrodes D1 and D2, with the positive electrode connected to D3. This causes the localized negative strain between the pair to shift the magnetic moment in the x' direction, or 45°. The connection between electrodes D1 and D2 is then disconnected, and the voltage removed. The free layer magnetic moment returns to the positive direction of the initial easy magnetization axis, or 90°. This achieves a reversible and repeatable 180° flip of the free layer magnetic moment.

[0030] Therefore, by using this pair of electrodes to apply different sequences of voltages, the magnetic moment can achieve different control effects, realizing a 180° flip of the free layer magnetic moment within the plane, thereby obtaining switching between high / low magnetoresistance states.

[0031] The beneficial effects of the present invention are as follows:

[0032] 1. The present invention utilizes the inverse magnetoelectric coupling effect between ferromagnetism and ferroelectricity to regulate the magnetic moment of the ferromagnetic layer, and realizes an ultra-low power consumption magnetic storage unit with pure voltage regulation by effectively cooperating with the electrode pair that applies the inverse magnetoelectric coupling effect.

[0033] 2. Based on a multiferroic heterostructure consisting of a magnetic tunnel junction / piezoelectric stretching layer, a pair of in-plane electrodes are designed on the top surface of the piezoelectric stretching layer, in the same plane as the tunnel junction, and a bottom electrode is fabricated on the bottom surface of the substrate. Using the single in-plane electrode and the bottom electrode, a voltage is applied perpendicularly to the piezoelectric stretching layer. This inverse magnetoelectric coupling effect allows the magnetic moment of the tunnel junction's free layer to rotate within 90° of its initial orientation. Furthermore, applying positive and negative voltages via a pair of in-plane electrodes introduces local strain, which can shift the magnetic moment to directions 45° and 135° from the initial orientation, respectively, thereby helping the magnetic moment overcome the 90° reversal barrier. Consequently, applying voltages regularly achieves reversible and repeatable 180° reversals of the magnetic moment, modulating the parallel and antiparallel states between the free and pinned layers, and achieving maximum tunnel magnetoresistance control, which is beneficial for the development of low-power voltage-controlled magnetic memory devices.

[0034] 3. The present invention introduces a pair of small-sized in-plane electrodes on the upper surface of the piezoelectric stretchable layer, which only occupies a small area and is conducive to the subsequent matching of the structure of the integrated magnetic random access memory. It has great potential in the practical application of ultra-low power voltage-controlled magnetic storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic cross-sectional view of the structure of a magnetic tunnel junction multilayer film according to an embodiment;

[0036] Figure 2 is a schematic diagram of the three-dimensional structure of a magnetic tunnel junction memory cell according to an embodiment;

[0037] Figure 3 Schematic diagram of the rotation of the free layer magnetic moment during the switching process between the parallel and antiparallel states of the magnetic tunnel junction;

[0038] Figure 4 is the high / low magnetoresistance state obtained by applying different voltages;

[0039] Reference numerals: 1 - lower electrode plate; 2 - piezoelectric stretch layer; 3 - buffer layer; 4 - free layer; 5 - oxide barrier layer; 6 - pinned layer; 7 - antiferromagnetic layer. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0042] Example 1

[0043] like Figures 1 to 4 As shown, this embodiment provides a method for implementing a voltage-controlled storage unit based on tunnel magnetoresistance, comprising the following steps:

[0044] Step 1: Select conventional PMN-PT(011) piezoelectric material as the piezoelectric stretch layer 2. Using a vacuum coating process, deposit Au (300 nm) at appropriate locations on the lower electrode plate surface of the substrate to serve as the bottom electrode D3, which applies a voltage to the substrate. When a voltage is applied to the piezoelectric stretch layer 2, the strain generated in the piezoelectric stretch layer 2 is volatile.

[0045] Step 2: Place the substrate in a magnetron sputtering device and use a thin film deposition process to deposit Ta (5nm) / CoFeB (3nm) / MgO (2nm) / CoFeB (3nm) / IrMn (15nm) tunnel junction thin film layers on the upper surface of the substrate, which are buffer layer 3 / free layer 4 / oxide barrier layer 5 / fixed layer 6 / antiferromagnetic layer 7, respectively. The structure is as follows: Figure 1 As shown in Figure 2 , during film deposition, an induced magnetic field H is applied along the substrate crystal axis

[001] , aligning the easy magnetization axis of the free layer 3 and the pinning direction of the antiferromagnetic layer 7 in the

[001] direction (set as the x-axis). The prepared sample is then microfabricated using photolithography into a small circular tunnel junction with a diameter of 10 μm.

[0046] Step 3: Use standard lift-off photolithography to prepare in-plane electrodes D1 and D2. The centerline direction of the two electrodes is 45° away from the x-axis in the plane, which is set as the x' direction. The y' direction is perpendicular to the x' direction and is 135° away from the x-axis in the plane. Use magnetron sputtering equipment to prepare Au (50nm) as the electrode film. After the film is sputtered, use acetone or a cleaning solution to remove the photoresist. The structural diagram is shown in the figure below. Figure 2 As shown in FIG2 , FIG2 is a schematic structural diagram of a magnetic tunnel junction memory cell according to an embodiment; wherein the cylinder in the middle of the substrate is a tunnel junction MTJ, and D1 , D2 , and D3 are electrodes for applying a voltage E to the substrate.

[0047] Step 4: Figure 3This is a schematic diagram of the switching between the parallel state and the antiparallel state of the magnetic tunnel junction. When controlling from the parallel state to the antiparallel state, first apply a +200V voltage to electrodes D1 and D2, and connect the negative electrode to D3. Positive strain will be generated in the middle area between electrodes D1 and D2. Because the ferromagnetic layer selected is CoFeB, which has a positive magnetostriction coefficient, an equivalent magnetic field will be generated along the x' direction. The magnetic moment of the free layer 3 of the tunnel junction is affected by the effective magnetic field and turns to the x' direction, that is, it deviates from the x-axis by 45° in the plane; then disconnect the connection of electrode D2, apply a +400V voltage to D1 and D3, and according to the inverse piezoelectric effect of the piezoelectric stretch layer, negative strain will be generated along the x direction. Through the inverse magnetoelectric coupling effect, the magnetic moment of the free layer 3 will turn to the y direction. (i.e., 90° away from the x-axis); then a -200V voltage is applied to the pair of electrodes D1 and D2, and the positive electrode is connected to D3. At this time, local negative strain will be generated in the area between the pair of electrodes D1 and D2, causing the magnetic moment to turn to the y' direction, that is, 135° away from the x-axis; then the connection between electrodes D1 and D2 is disconnected, and the voltage is removed. At this time, the magnetic moment of the free layer 3 will return to the negative direction of the initial easy magnetization axis, that is, 180° direction, thereby realizing the reversal of the magnetic moment of the free layer 3 from 0° to 180°, and becoming anti-parallel to the fixed layer 5. Next, a +200V voltage is applied to electrodes D1 and D2, with the negative terminal connected to D3. This creates a localized positive strain between electrodes D1 and D2, causing the magnetic moment to deviate from the negative x-axis to the x' direction (i.e., 225°). Electrode D2 is then disconnected, and a +400V voltage is applied to electrodes D1 and D3. This generates a negative strain along the x-direction, causing the magnetic moment of the free layer 3 to shift toward the y-axis (i.e., 270°). Next, a -200V voltage is applied to electrodes D1 and D2, with the positive terminal connected to D3. This creates a localized negative strain between electrodes D1 and D2, causing the magnetic moment to shift toward the y' direction (i.e., 315°). Electrodes D1 and D2 are then disconnected and the voltage removed. The magnetic moment of the free layer 3 returns to the positive direction of its initial easy magnetization axis, i.e., 360° (0°). The free layer 3 returns to a parallel state with the pinned layer 5, completing the transition from the antiparallel state to the parallel state. Figure 4 Demonstrated the switching of low / high resistance states of tunnel magnetoresistance by applying different voltages, thereby realizing voltage-controlled tunnel magnetoresistance storage. Figure 4 The high / low magnetoresistance states are obtained by applying different voltages; wherein, ±200V voltages are applied to the electrodes D1, D2, and D3, and +400V voltage is applied to the electrodes D1 and D3.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for realizing a voltage-controlled storage unit based on tunnel magnetoresistance, characterized in that: The following steps are involved: Step 1: selecting a piezoelectric telescopic layer (2) for piezoelectric electromagnetic storage, wherein the piezoelectric telescopic layer (2) is capable of generating negative strain in the crystal axis direction of the piezoelectric telescopic layer (2) when voltage is applied to the upper and lower surfaces thereof, whether it is a positive voltage or a negative voltage, and the [001] crystal axis direction is set as the x direction; Step 2: preparing a magnetic tunnel junction film on the upper surface of the piezoelectric telescopic layer (2), and sequentially preparing a buffer layer (3), a free layer (4), an oxide barrier layer (5), a fixed layer (6), and an antiferromagnetic layer (7) from the piezoelectric telescopic layer (2); When voltage is applied, the magnetic moment of the free layer (4) rotates according to the magnitude of the magnetoelastic coupling energy due to the magnetoelectric coupling effect, while the magnetic moment of the fixed layer (6) is basically unaffected; Step 3: Prepare a pair of electrodes D1 and D2 on the upper surface of the piezoelectric stretch layer (2). The two electrodes are of the same size, parallel to each other and distributed on both sides of the tunnel junction. The center line of the two electrodes is the x' direction, which deviates 45 degrees from the x-axis in the plane. The direction perpendicular to the x' direction is the y' direction, which deviates 135 degrees from the x-axis. At the same time, another electrode D3 is prepared on the surface of the lower electrode plate (1) for voltage application, wherein the electrode plate and electrode materials are selected from Cu, Ag, and Au. Step 4: When the magnetostriction coefficient of the magnetic material of the free layer (4) used for tunnel junction preparation is positive, in the initial state, the initial magnetic moment of the magnetic film of the free layer (4) is set in the positive direction of the x-axis. By applying voltage to the pair of electrodes D1 and D3, the initial magnetic moment of the free layer (4) can be turned to the y-axis direction due to the inverse magnetoelectric coupling effect. Applying positive and negative voltages to the pair of electrodes D1 and D2 can make the initial magnetic moment of the free layer (4) turn to the x' and y' directions respectively. Electrode D1 is connected to switch K1, and electrode D2 is connected to switch K2. Switch K1 and switch K2 are electrically connected via a connecting wire. The connecting wire between switch K1 and switch K2 is electrically connected to the positive electrode of power supply E, and electrode D3 is electrically connected to the negative electrode of the power supply. When the magnetostriction coefficient of the free layer (4) magnetic material used for tunnel junction preparation is negative, in the initial state, the initial magnetic moment of the magnetic film of the free layer (4) is set in the positive direction of the y-axis. By applying a voltage to the pair of electrodes D1 and D3, the initial magnetic moment of the free layer (4) can be turned to the x-axis direction due to the reverse magnetoelectric coupling effect. Applying positive and negative voltages to the pair of electrodes D1 and D2 can make the initial magnetic moment of the free layer (4) turn to the y' and x' directions respectively.

2. The method for realizing a voltage-controlled storage unit based on tunnel magnetoresistance according to claim 1, characterized in that: In the step 1, the piezoelectric material used in the piezoelectric telescopic layer (2) is PMN-PT or PZN-PT.

3. The method for realizing a voltage-controlled storage unit based on tunnel magnetoresistance according to claim 2, characterized in that: Au is deposited at an appropriate position on the surface of the lower electrode plate (1) of the piezoelectric telescopic layer (2) using a vacuum coating process to serve as a bottom electrode D3 for applying a voltage to the piezoelectric telescopic layer (2); when a voltage is applied to the piezoelectric telescopic layer (2), the strain generated by the piezoelectric telescopic layer (2) is volatile.

4. The method for realizing a voltage-controlled storage unit based on tunnel magnetoresistance according to claim 1, characterized in that: In step 2, an induced magnetic field H can be applied during the film preparation process to set the easy magnetization axis direction of the free layer (4), and the easy axis of the free layer (4) is set along the x-axis direction.

5. The method for realizing a voltage-controlled storage unit based on tunnel magnetoresistance according to claim 1, characterized in that: In step 3, the in-plane electrodes D1 and D2 are prepared using a standard lift-off photolithography process. The centerline direction of the two electrodes is 45° away from the x-axis in the plane, which is set as the x' direction. The y' direction is perpendicular to the x' direction and is 135° away from the x-axis in the plane. Au is prepared as the electrode film using magnetron sputtering equipment, and the photoresist is removed using acetone or a cleaning solution after the film is sputtered.

6. The method for realizing a voltage-controlled storage unit based on tunnel magnetoresistance according to claim 1, characterized in that: The materials of the free layer (4) and the fixed layer (6) are CoFe, Co, CoFeB or NiFe, wherein the coercive field of the free layer (4) should be smaller than that of the fixed layer (6), and the free layer (4) should be made of a magnetic material with large magnetostriction to ensure the response of magnetoelectric coupling.

7. The method for realizing a voltage-controlled storage unit based on tunnel magnetoresistance according to claim 1, characterized in that: When the initial magnetic moment of the magnetic film of the free layer (4) is set in the positive direction of the x-axis; when a positive voltage is applied to the pair of electrodes D1 and D2 on the piezoelectric telescopic layer (2), switches K1 and K2 are closed; the negative electrode is connected to D3, and then a local positive strain is generated in the region between the pair of electrodes D1 and D2, causing the magnetic moment to deviate from the x-axis direction and be oriented in the x' direction of the line connecting the centers of the two electrodes, that is, deviate from the x-axis direction by 45°; then the connection of electrode D2 is disconnected, switch K2 is opened, and voltage is applied to electrodes D1 and D3. According to the piezoelectric effect of the selected piezoelectric telescopic layer (2), a negative strain is generated along the crystal axis direction of the piezoelectric telescopic layer (2). Through the inverse magnetoelectric coupling effect, the magnetic moment of the free layer (4) is affected by the strain and turned to the y direction, that is, deviated from the x-axis by 90°; Then, a negative voltage is applied to the pair of electrodes D1 and D2, switches K1 and K2 are closed, and the positive electrode is connected to D3. At this time, a local negative strain will be generated in the area between the pair of electrodes D1 and D2, causing the magnetic moment to turn to the y' direction perpendicular to the center line of the electrodes D1 and D2, that is, 135° away from the x-axis; then the connection between electrodes D1 and D2 is disconnected, and the voltage is removed. At this time, the magnetic moment of the free layer (4) will return to the negative direction of the initial easy magnetization axis, that is, the 180° direction, thereby realizing the reversal of the magnetic moment of the free layer (4) from 0° to 180°.

8. The method for realizing a voltage-controlled storage unit based on tunnel magnetoresistance according to claim 7, characterized in that: When the magnetic moment of the free layer (4) is to be flipped from 180° to 0°, a positive voltage is first applied to electrodes D1 and D2, and the negative electrode is connected to D3. At this time, the local positive strain between the pair of electrodes D1 and D2 causes the magnetic moment to deviate from the negative direction of the x-axis and align in the x' direction of the center line connecting the two electrodes, that is, in the 225° direction; then the connection of electrode D2 is disconnected, and a positive voltage is applied to electrodes D1 and D3. At this time, a negative strain is generated in the x-direction, and the magnetic moment of the free layer will turn to the y-axis direction, that is, in the 270° direction; Then, a negative voltage is applied to the pair of electrodes D1 and D2, and the positive electrode is connected to D3. At this time, the local negative strain between the pair of electrodes D1 and D2 causes the magnetic moment to turn to the y' direction, that is, the 315° direction; then the connection between the electrodes D1 and D2 is disconnected, and the voltage is removed. At this time, the magnetic moment of the free layer (4) will return to the positive direction of the initial easy magnetization axis, that is, the 360° or 0° direction; thereby achieving a reversible and repeatable 180° flip of the magnetic moment of the free layer (4).

9. The method for realizing a voltage-controlled storage unit based on tunnel magnetoresistance according to claim 1, characterized in that: When the initial magnetic moment of the magnetic film of the free layer (4) is set in the positive direction of the y-axis, that is, in the 90° direction within the plane; when a positive voltage is applied to the pair of electrodes D1 and D2 on the substrate, and the negative electrode is connected to D3, then the region between the pair of electrodes D1 and D2 will produce a local positive strain, causing the magnetic moment to deviate from the y-axis direction and be oriented perpendicular to the y' direction of the electrode center line, that is, in the 135° direction; then the connection of electrode D2 is disconnected, and a positive voltage is applied to the electrodes D1 and D3, then a negative strain is generated along the crystal axis direction of the piezoelectric stretching layer (2), and through the inverse magnetoelectric coupling effect, the magnetic moment of the free layer (4) will be affected by the strain and turned to the x direction, that is, in the 180° direction; Then, a negative voltage is applied to the pair of electrodes D1 and D2, and the positive electrode is connected to D3. At this time, a local negative strain will be generated in the area between the pair of electrodes D1 and D2, causing the magnetic moment to turn to the x' direction of the electrode center line, that is, the 225° direction; then the connection between electrodes D1 and D2 is disconnected, and the voltage is removed. At this time, the magnetic moment of the free layer (4) will return to the negative direction of the initial easy magnetization axis, that is, the 270° direction, thereby achieving a 180° reversal of the free layer magnetic moment.

10. The method for realizing a voltage-controlled storage unit based on tunnel magnetoresistance according to claim 9, characterized in that: Apply a positive voltage to electrodes D1 and D2, and connect the negative electrode to D3. At this time, the local positive strain between the electrodes D1 and D2 causes the magnetic moment to deviate from the negative direction of the y-axis and align in the y' direction, i.e., the 315° direction. Then disconnect the electrode D2 and apply a positive voltage to the electrodes D1 and D3. At this time, a negative strain is generated in the x-direction, and the magnetic moment of the free layer (4) will turn to the x-axis direction, i.e., the 0° direction. Then, a negative voltage is applied to the pair of electrodes D1 and D2, and the positive electrode is connected to D3. At this time, the local negative strain between the pair of electrodes D1 and D2 causes the magnetic moment to turn to the x' direction, that is, the 45° direction; then the connection between the electrodes D1 and D2 is disconnected, and the voltage is removed. At this time, the magnetic moment of the free layer (4) will return to the positive direction of the initial easy magnetization axis, that is, the 90° direction; thereby, a reversible and repeatable 180° flip of the magnetic moment of the free layer (4) is achieved; Therefore, by applying different sequences of voltages to the pair of electrodes, the magnetic moment can achieve different control effects, and the magnetic moment of the free layer (4) can be flipped 180 degrees in the plane, thereby obtaining the switching of high / low magnetoresistance states.

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