Spin orbit torque magnetic memory based on voltage controlled magnetic anisotropy effect

Abstract

The application discloses a spin orbit torque magnetic memory based on a voltage-controlled magnetic anisotropy effect, which comprises an electrode layer and an SOT-MTJ (spin orbit torque magnetic tunnel junction) from top to bottom, wherein the SOT-MTJ comprises an artificial antiferromagnetic coupling layer, a reference layer, a tunneling layer, a free layer and an antiferromagnetic layer which are sequentially stacked from top to bottom. In the SOT-MTJ, an angle is formed between the long axis direction of the elliptical upper layer and the X axis direction of the bottom layer to generate a channel of an effect field Heff, and an auxiliary magnetic moment is more easily flipped. The bottom antiferromagnetic layer is made of IrMn or PtMn material, has a relatively large spin Hall angle, is beneficial to efficiently generating a spin orbit torque to flip a magnetic moment, and meanwhile, the IrMn and PtMn antiferromagnetic material can provide an exchange coupling field to replace an external field required by a coherent magnetic switch. In addition, a voltage is applied to the top and bottom of the magnetic memory, a very short voltage pulse is applied, an energy barrier during magnetization switching is reduced or even eliminated, and the free layer is induced to realize SOT deterministic switching faster.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnetic memory, and particularly relates to a spin-orbit torque magnetic memory based on a voltage-controlled magnetic anisotropy effect. BACKGROUND

[0002] Magnetic random access memory (MRAM) is considered as one of the most promising emerging storage technologies due to its high storage density, high read / write speed, ultra-long durability, and data non-volatility. With the rapid development of information processing and storage technology, higher requirements are put forward for the performance of magnetic random access memory. In particular, the discovery of spin transfer torque effect (STT) and spin-orbit torque (SOT) makes the spin-related effect in magnetic tunnel junction a hot research topic. At present, the magnetic random access memory (STT-MRAM) based on the STT effect has been mass-produced and applied in commercial applications. However, the STT-MRAM is not suitable for implementation in higher memory levels due to its high energy consumption, delay, and durability. The practical application of the spin-orbit torque magnetic random access memory (SOT-MRAM) based on the SOT effect still has difficulties.

[0003] Spin-orbit torque (SOT) is generated by materials with strong spin-orbit coupling (SOC), such as heavy metals, topological insulators, etc. Compared with spin transfer torque (STT), the magnetization operation using SOT shows great potential for the next generation of magnetic random access memory (MRAM). SOT-MRAM has the advantages of low power consumption, fast write / read speed, and improved durability. However, in the PMA system, the use of SOT to achieve deterministic switching requires an in-plane magnetic field (Hx) along the current direction to break the symmetry. The requirement of in-plane magnetic field poses great problems for the preparation and integration of devices. Therefore, the realization of a vertical spin-orbit switching method without external magnetic field is an urgent direction for the industry to explore. SUMMARY

[0004] The present application is proposed to solve the problems of the prior art. The present application provides a spin-orbit torque magnetic memory based on a voltage-controlled magnetic anisotropy effect. The VCMA effect is used to reduce switching energy to assist the SOT effect in the MTJ switching combination method. The present application realizes efficient and ultra-fast SOT switching applications, solves the problems of large write current, high power consumption, and non-separation of read and write in STT-MTJ switching, and the problems of slow SOT-MTJ flipping speed and the need for an external in-plane magnetic field to achieve deterministic flipping.

[0005] Technical solution: In order to solve the above technical problems, the application provides a spin orbit torque magnetic memory based on a voltage-controlled magnetic anisotropy effect, characterized in that: the magnetic memory structure comprises, from top to bottom, an electrode layer, a vertical spin orbit torque-magnetic tunnel junction (SOT-MTJ), the SOT-MTJ comprises, from top to bottom, an artificial antiferromagnetic coupling layer, a reference layer, a tunneling layer, a free layer and an antiferromagnetic layer which are stacked in layers, the electrode layer adopts Cu, the artificial antiferromagnetic coupling layer adopts a [Co / Pt]6 / Ru / [Co / Pt]4 multilayer thin film material, the reference layer and the free layer both adopt CoFeB material, the tunneling layer adopts MgO material, and the antiferromagnetic layer adopts IrMn or PtMn material; a voltage pulse with a time of 0.7 ns and an amplitude of 1.2 V-1.5 V is applied to the top layer of the electrode layer and the bottom of the vertical spin orbit torque-magnetic tunnel junction, and the position between the bottom antiferromagnetic layer and the layers above the magnetic tunnel junction in the vertical spin orbit torque-magnetic tunnel junction is inclined, and the inclination angle is β, and the inclination angle β is between 10° and 45°.

[0006] As a preferred technical solution of the application, the top electrode material is Cu, and the thickness is 1.5-3 nm.

[0007] As a preferred technical solution of the application, the artificial synthetic antiferromagnetic layer is a [Co / Pt]6 / Ru / [Co / Pt]4 multilayer thin film structure, which is used as a pinning layer to fix the magnetization direction of the ferromagnetic layer, and the thickness is 6.3-7.09 nm.

[0008] As a preferred technical solution of the application, the reference layer and the free layer are CoFeB material, and the thickness is 0.9-2 nm, which is used to realize magnetization reversal storage data.

[0009] As a preferred technical solution of the application, the tunneling layer adopts MgO material, and the thickness is 1-3 nm, which has a good tunneling magnetoresistance effect and is used to generate a tunneling effect to transmit a spin signal.

[0010] As a preferred technical solution of the application, the antiferromagnetic layer adopts IrMn or PtMn, and is placed at the bottom of the MTJ, and the thickness is 3.5-5 nm, because IrMn and PtMn both have a considerable spin Hall angle, which is conducive to efficiently generating a spin orbit torque to reverse the magnetic moment, and can provide an exchange bias field, which can assist in realizing SOT switching without an external magnetic field.

[0011] As a preferred technical scheme of the application: the data write operation of the new magnetic tunnel junction memory device is accomplished by injecting positive and negative currents Iwrite into the bottom anti-ferromagnetic layer to change the magnetization state of the free layer, thereby realizing the writing of data "0" and "1"; and the data read operation is accomplished by reading current Iread through the tunneling layer, and according to the high and low resistance states of the tunnel magnetoresistance effect (TMR), the size of the output current is judged by loading the same voltage to judge whether the data information of the memory is "0" or "1".

[0012] The principle of the application is that the spin-orbit torque magnetic memory based on the pressure-controlled magnetic anisotropy effect is to realize deterministic switching by using the pressure-controlled magnetic anisotropy effect to assist the spin-orbit torque. Specifically, current is injected into the bottom anti-ferromagnetic layer, and due to the spin Hall effect (SHE), the in-plane charge current flowing in the IrMn or PtMn layer is converted into a vertical spin current, and the spin current will exert a spin torque on the free layer. Since the IrMn and PtMn anti-ferromagnetic materials produce exchange bias field, the free layer magnetic moment flips without the need for external magnetic field assistance. In order to make the vertical magnetic tunnel junction switching speed faster, in the memory structure, the bottom anti-ferromagnetic layer and the upper magnetic tunnel junction layers are inclined, the inclination angle β is between 10°-45°, the SOT-MTJ top layer and the bottom are applied with a voltage pulse with a time of 0.7 ns and an amplitude of 1.2V-1.5V, the interface perpendicular magnetic anisotropy (PMA) is reduced, thereby reducing or even eliminating the energy barrier between the parallel (P) and anti-parallel (AP) states during magnetization switching. The change in structure makes the flipping speed faster and the energy required for flipping lower. The application reduces the power consumption of the magnetic memory, improves the spin conversion rate, stability and running speed, and has good energy performance.

[0013] Advantages: Compared with the prior art, the technical scheme of the application has the following advantages:

[0014] 1. The memory of the application uses IrMn or PtMn as an anti-ferromagnetic layer: the discovery of spin-orbit torque provides a novel magnetic moment control mode and data writing method for magnetic random memory. Due to the existence of spin Hall effect, non-polarized in-plane charge current can produce vertical spin current, and then produce spin accumulation on the thin film interface. When this spin current or spin accumulation is absorbed by the adjacent ferromagnetic layer, the spin-orbit torque is sufficient to cause the magnetic moment to flip deterministically, i.e. the spin-orbit torque can realize the writing of spin information. The spin Hall angle characterizes the conversion efficiency of charge current to spin current in the material, and is defined as where J s is the spin current density, θ SH is the spin Hall angle, J CJ is the charge current density, s is the spin polarization direction vector, e is the electron charge, is the simplified Plank constant. It can be seen that the larger the spin Hall angle is, the higher the efficiency of the conversion of the charge current into the spin current is. IrMn and PtMn have a relatively large spin Hall angle, which is very beneficial to efficiently generating a spin-orbit torque to flip a magnetic moment and improve the flipping speed, and can also provide an exchange bias field to assist in realizing a SOT deterministic flipping without an external magnetic field.

[0015] 2. The memory structure of the present application adopts an angle tilt: on the memory structure, the bottom antiferromagnetic layer in the SOT-MTJ and the layers of the magnetic tunnel junction placed above are tilted: the long axis of the elliptical free layer and the transverse horizontal line-X axis direction of the antiferromagnetic layer (AFM) form an angle β to prevent the disappearance of the effective field Heff. When the perpendicular magnetic anisotropy (PMA) is removed by the VCMA voltage pulse, Heff induces M magnetic moment precession, and the vertical spin-orbit torque magnetic tunnel junction (SOT-MTJ) can be switched without an external field, which is beneficial to device flipping, thereby improving the spin-orbit torque (SOT) efficiency.

[0016] 3. The memory of the present application has a read-write separation function: the bottom antiferromagnetic layer is connected to the positive and negative electrodes, and the change of the magnetization state of the free layer is completed by injecting a positive or negative current Iwrite, thereby realizing the writing of data "0" or "1". When a positive current Iwrite is injected to make the direction of the free layer magnetic moment change from the parallel state to the antiparallel state, the resistance of the MTJ is in a high resistance state, that is, "1" is written by the current; when a negative current Iwrite is injected to make the direction of the free layer magnetic moment change from the antiparallel state to the parallel state, the resistance of the MTJ is in a low resistance state, that is, "0" is written by the current. The data reading operation is to inject a current into the bottom antiferromagnetic layer and generate a spin-orbit coupling effect, and then read the current Iread through the tunneling layer. Due to the tunneling magnetoresistance effect (TMR), according to the high and low resistance states described above, the same voltage is loaded to judge the size of the output current, thereby judging the data information of the memory as "0" or "1". In this way, the read-write separation operation is realized, the damage of the current to the barrier layer in the tunnel junction is reduced, and the function of reading and writing without an external magnetic field is completed.

[0017] 4. The magnetic memory of the present application allows field-free switching SOT at a lower current, has the characteristics of low power consumption and fast switching speed, and when a read voltage opposite to the write assist is applied, the perpendicular magnetic anisotropy (PMA) increases, further limiting the interference received during the reading process, and the stability is good. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1is a perspective view schematic diagram of a spin orbit torque magnetic memory structure based on a voltage-controlled magnetic anisotropy effect of the present application.

[0019] Figure 2 is a cross-sectional schematic diagram of a spin orbit torque magnetic memory structure based on a voltage-controlled magnetic anisotropy effect of the present application.

[0020] Figure 3 is a top view of a spin orbit torque magnetic memory structure based on a voltage-controlled magnetic anisotropy effect of the present application. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the drawings. However, the present application is not limited to these specific embodiments, and any person skilled in the art can make some modifications to the present application to achieve similar results, and these modifications are also included in the present application.

[0022] Example 1:

[0023] The present application provides a spin orbit torque magnetic memory based on a voltage-controlled magnetic anisotropy effect, the magnetic memory structure sequentially includes an electrode layer, an SOT-MTJ (spin orbit torque magnetic tunnel junction) from top to bottom, the SOT-MTJ includes an artificial antiferromagnetic coupling layer, a reference layer, a tunneling layer, a free layer and an antiferromagnetic layer stacked from top to bottom. The electrode material uses Cu material, the thickness is 1.5 nm, the artificial synthetic antiferromagnetic coupling layer uses [Co / Pt]6 / Ru / [Co / Pt]4 multilayer thin film material, the thickness is 6.3 nm, the reference layer and the free layer both use CoFeB material, the thickness is 0.9 nm, the tunneling layer uses MgO material, the thickness is 1.7 nm, the antiferromagnetic layer uses IrMn material, the thickness is 3.5 nm, IrMn has a relatively large spin Hall angle, which is conducive to efficiently generating spin orbit torque to flip the magnetic moment, and can provide an exchange bias field, which can assist to realize switching without an external magnetic field. The top layer and the bottom of the SOT-MTJ are applied with a voltage pulse with a time of 0.7 ns and an amplitude of 1.2 V, in the SOT-MTJ, the long axis direction of the elliptical upper layer and the horizontal line-X axis direction of the bottom antiferromagnetic layer (AFM) form an angle β, β is 10°.

[0024] As a preferred technical scheme of the present application: the data write operation of the new magnetic tunnel junction memory device is to change the magnetization state of the free layer by injecting positive and negative currents Iwrite into the bottom antiferromagnetic layer, thereby realizing the writing of data "0" and "1"; and the data read operation is to read the current Iread through the tunneling layer, and according to the high and low resistance states of the tunnel magnetoresistance effect (TMR), the size of the output current is judged by loading the same voltage, so as to judge whether the data information of the memory is "0" or "1".

[0025] Embodiment 2:

[0026] The application provides a spin-orbit torque magnetic memory based on a voltage-controlled magnetic anisotropy effect, and the magnetic memory structure comprises, from top to bottom, an electrode layer and an SOT-MTJ (spin-orbit torque magnetic tunnel junction). The SOT-MTJ comprises, from top to bottom, an artificial antiferromagnetic coupling layer, a reference layer, a tunneling layer, a free layer and an antiferromagnetic layer which are stacked in sequence. The electrode material is Cu material with a thickness of 1.5 nm, the artificial antiferromagnetic coupling layer is [Co / Pt]6 / Ru / [Co / Pt]4 multilayer film material with a thickness of 6.3 nm, the reference layer and the free layer are both CoFeB material with a thickness of 0.9 nm, the tunneling layer is MgO material with a thickness of 1.7 nm, and the antiferromagnetic layer is PtMn material with a thickness of 3.5 nm. The PtMn has a relatively large spin Hall angle, is beneficial to efficiently generating spin-orbit torque to flip the magnetic moment, can provide an exchange bias field, and can assist in realizing switching without an external magnetic field. The SOT-MTJ top layer and the bottom layer are subjected to a voltage pulse with a time of 0.7 ns and an amplitude of 1.2 V. The SOT-MTJ has an elliptical upper layer, and the long axis direction of the upper layer and the transverse horizontal line-X axis direction of the bottom antiferromagnetic layer (AFM) form an angle β, and β is 45°.

[0027] The data write operation of the new magnetic tunnel junction memory device is to change the magnetization state of the free layer by injecting positive and negative currents Iwrite into the bottom antiferromagnetic layer, thereby realizing the writing of data "0" and "1"; and the data read operation is to read the current Iread through the tunneling layer, and according to the high and low resistance states of the tunnel magnetoresistance effect (TMR), the size of the output current is judged by loading the same voltage, so as to judge whether the data information of the memory is "0" or "1".

[0028] In addition, it should be understood that, although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the specification is described in this way only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A spin-orbit torque magnetic memory based on a voltage-controlled magnetic anisotropy effect, characterized in that: The magnetic memory structure comprises, from top to bottom, an electrode layer, a perpendicular spin-orbit torque-magnetic tunnel junction (SOT-MTJ), the SOT-MTJ comprising, from top to bottom, a synthetic antiferromagnetic coupling layer, a reference layer, a tunneling layer, a free layer and an antiferromagnetic layer, the electrode layer being made of Cu, the synthetic antiferromagnetic coupling layer being made of a [Co / Pt]6 / Ru / [Co / Pt]4 multilayer film material, the reference layer and the free layer both being made of a CoFeB material, the tunneling layer being made of a MgO material, and the antiferromagnetic layer being made of an IrMn or PtMn material; a voltage pulse with a time of 0.7 ns and an amplitude of 1.2 V-1.5 V is applied to the top layer of the electrode layer and the bottom of the perpendicular spin-orbit torque-magnetic tunnel junction, and in the perpendicular spin-orbit torque-magnetic tunnel junction, the position between the bottom antiferromagnetic layer and the layers above the magnetic tunnel junction is inclined, and the inclination angle is β.

2. The spin-orbit torque magnetic memory based on the voltage-controlled magnetic anisotropy effect according to claim 1, wherein: The free layer, the tunneling layer, the reference layer and the synthetic antiferromagnetic coupling layer in the perpendicular spin-orbit torque-magnetic tunnel junction are in an elliptical shape.

3. The spin-orbit torque magnetic memory based on the voltage-controlled magnetic anisotropy effect according to claim 1, wherein: In the perpendicular spin-orbit torque-magnetic tunnel junction, the long axis direction of the elliptical upper layer and the X axis direction of the bottom antiferromagnetic layer form an angle β, and the angle range is 10°-45°.

4. The spin-orbit torque magnetic memory based on the voltage-controlled magnetic anisotropy effect according to claim 1, wherein: The thickness of the electrode material layer is 1.5-3 nm.

5. The spin-orbit torque magnetic memory based on the voltage-controlled magnetic anisotropy effect according to claim 1, wherein: At room temperature, the thickness of the synthetic antiferromagnetic coupling layer is 6.3-7.09 nm.

6. The spin-orbit torque magnetic memory based on the voltage-controlled magnetic anisotropy effect according to claim 1, wherein: The thickness of the reference layer and the free layer is 0.9-2 nm.

7. The spin-orbit torque magnetic memory based on voltage-controlled magnetic anisotropy effect according to claim 1, characterized in that: The thickness of the tunneling layer is 1-3 nm.

8. The spin-orbit torque magnetic memory based on the voltage-controlled magnetic anisotropy effect according to claim 1, wherein: The thickness of the antiferromagnetic layer is 3.5-5 nm.

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