Magnetic tunnel junction memory device based on bismuth selenide and nickel iodide heterojunction substrate

Abstract

This application discloses a magnetic tunnel junction memory device based on a bismuth selenide and nickel iodide heterojunction substrate. The memory includes, from top to bottom, a top electrode, a SOT-MTJ, and a substrate. The SOT-MTJ includes, from top to bottom, a reference layer, a tunneling layer, a heavy metal layer, and a free layer. The substrate is a Bi2Se3 and NiI2 heterojunction structure. Bi2Se3 facilitates the conversion of current into spin-orbit torque, enabling current-induced field-free magnetization reversal. NiI2 has vertical magnetic anisotropy, which can reduce the critical reversal current. An artificial antiferromagnetic structure (CoFeB / MgO / Ta / W / CoFeB) with vertical magnetic anisotropy is adopted, with Ta / W composite heavy metal as the coupling layer. The two antiferromagnetically coupled CoFeB layers switch between parallel and antiparallel states under the action of SOT. Both Ta and W have large spin Hall angles, which are very beneficial for generating spin-orbit torque to reverse the magnetic moment.

Description

Technical Field

[0001] This invention relates to the field of magnetic memory technology, and more specifically to magnetic tunnel junction memory devices based on bismuth selenide and nickel iodide heterojunction substrates. Background Technology

[0002] In 1975, Julliere observed the TMR effect in Co / Ge / Fe magnetic tunnel junctions (MTJs). The TMR effect, with its unique advantages such as high magnetoresistivity and high magnetic field sensitivity, shows very promising application prospects. In summary, TMR materials are mainly used in the read heads of computer hard drives, MRAM, and various magnetic sensors. MRAM based on the TMR effect has advantages such as high integration density, non-volatility, fast read / write speeds, a large number of rewritable cycles, strong radiation resistance, low power consumption, and long lifespan. It can be used as both internal and external memory in computers. As internal memory, compared with commercially available semiconductor internal memory, its advantages are non-volatility, fast access speed, and strong radiation resistance; as external memory, it is 1000 times faster than Flash memory, with low power consumption and long lifespan. Compared with hard disks, its advantage is the absence of moving parts, making it as convenient to use as Flash memory. TMR materials can also be used to make various high-sensitivity magnetic sensors for detecting and sensing weak magnetic field signals. Due to their small size, high reliability, and wide response range, these sensors have broad application prospects in automation technology, home appliances, trademark recognition, satellite positioning, navigation systems, and precision measurement technology. Summary of the Invention

[0003] Technical problem to be solved: In order to overcome the shortcomings of the prior art, this application proposes a magnetic tunnel junction memory device based on a bismuth selenide and nickel iodide heterojunction substrate, so as to solve the problems of small spin Hall angle, poor stability and inability to achieve read-write separation in the prior art magnetic random access memory.

[0004] Technical solution: A magnetic tunnel junction memory device based on a bismuth selenide and nickel iodide heterojunction substrate. The magnetic tunnel junction memory device based on a bismuth selenide and nickel iodide heterojunction substrate includes a top electrode, a SOT-MTJ and a substrate arranged sequentially from top to bottom. The SOT-MTJ includes a reference layer, a tunneling layer, a composite heavy metal layer and a free layer arranged sequentially from top to bottom. The top electrode is made of aluminum or copper, the reference layer and the free layer are both made of CoFeB, the tunneling layer is made of MgO, the composite heavy metal layer is formed by growing a tungsten thin layer on a tantalum thin layer to form a Ta / W composite material, and the substrate is a Bi2Se3 and NiI2 heterojunction structure.

[0005] As a preferred technical solution of this application, the top electrode material is aluminum with a thickness of 10 nm.

[0006] As a preferred technical solution of this application, the reference layer and the free layer are made of CoFeB material with a thickness of 2nm, which is used to realize magnetization flipping to store data.

[0007] As a preferred technical solution of this application, the tunneling layer is made of MgO material with a thickness of 2nm, and is used to generate a tunneling effect to transmit spin signals.

[0008] As a preferred technical solution of this application, the composite heavy metal layer is made of Ta / W and placed between the tunneling layer and the free layer. Its thickness is 2nm. Since both Ta and W have large spin Hall angles, they are conducive to generating spin orbital torque to flip the magnetic moment.

[0009] As a preferred technical solution of this application: the substrate adopts a Bi2Se3 / NiI2 heterojunction structure. The Bi2Se3 / NiI2 heterojunction has a relatively large spin Hall conductivity, which is suitable for the conversion of current and spin-orbit torque. In order to improve the conversion efficiency of current and spin-orbit torque, the thickness of the Bi2Se3 / NiI2 heterojunction is 9nm.

[0010] As a preferred technical solution of this application: the data writing operation of the novel magnetic tunnel junction storage device is performed by injecting positive and negative currents I into the bottom electrode respectively. write This is done to change the magnetization state of the free layer, thereby enabling the writing of data 0 and 1; while the data reading operation is performed by transferring the read current I flowing through the SOT-MTJ. read The data stored therein is determined by comparing it with a reference current.

[0011] The principle of this invention is as follows: a novel tilted magnetic tunnel junction (TMR) memory device based on a Bi₂Se₃ / NiI₂ heterojunction substrate utilizes the TMR effect to store data. The TMR effect is a spin-dependent tunneling effect. If the magnetization directions of the two ferromagnetic layers are parallel, electrons from the majority spin subbands in one magnetic layer will enter empty states in the majority spin subbands of the other magnetic layer, and electrons from the minority spin subbands will also enter empty states in the minority spin subbands of the other magnetic layer, resulting in a large total tunneling current. If the magnetization directions of the two magnetic layers are antiparallel, the situation is reversed; that is, electrons from the majority spin subbands in one magnetic layer will enter empty states in the minority spin subbands of the other magnetic layer, and electrons from the minority spin subbands will also enter empty states in the majority spin subbands of the other magnetic layer, resulting in a smaller tunneling current. Therefore, the tunneling conductance changes with the magnetization directions of the two ferromagnetic layers, with higher conductance when the magnetization vectors are parallel than when they are antiparallel. Applying an external magnetic field can change the magnetization direction of the two ferromagnetic layers, thereby changing the tunneling resistance and leading to the TMR effect.

[0012] Beneficial effects: 1. Bi2Se3 / NiI2: Compared to planar magnetic anisotropy, perpendicular magnetic anisotropy is more conducive to realizing high-density information storage devices with low energy consumption and high thermal stability. Monolayer NiI2 has perpendicular magnetic anisotropy, which is beneficial for magnetization reversal and reducing energy consumption. The topological insulator material Bi2Se3 has a relatively large spin Hall angle, which can improve the conversion between current and spin-orbit torque, reduce power consumption, and improve magnetization reversal efficiency. Studying the spin characteristics of Bi2Se3 / NiI2 heterojunction, it can be found that the heterojunction has a relatively large SHC at E=-0.85eV, which can reach 1200(ℏ / e) S / cm, making it easier to generate SHE, thereby improving SOT efficiency. Furthermore, the size of SHC can be controlled by controlling the Fermi energy transfer, thereby controlling SOT.

[0013] 2. Ta / W Composite Heavy Metal Layer: Due to the spin Hall effect, the introduction of a non-polarized in-plane charge flow can generate a vertical spin current, leading to spin accumulation at the thin film interface. When this spin current or spin accumulation is absorbed by an adjacent ferromagnetic layer, the resulting spin-orbit torque is sufficient to deterministically reverse the magnetic moment, meaning the spin-orbit torque can write spin information. The efficiency of a specific material in generating spin-orbit torque is closely related to its spin Hall angle. The spin Hall angle is defined as the ratio of spin conductivity to charge conductivity. Both Ta and W have large spin Hall angles, which are highly favorable for generating spin-orbit torque to reverse the magnetic moment. The composite heavy metal layer has good heat resistance, high vertical magnetic anisotropy, and an effective spin Hall angle as high as 0.5, providing an effective approach for the practical application of SOT devices. Introducing W intercalation into Ta / CoFeB increases the system's spin Hall angle and reduces the auxiliary external field required for current-induced magnetization reversal.

[0014] 3. Read / Write Separation: The two ends of the Bi2Se3 / NiI2 conductive layer are connected to the positive and negative electrodes. Note: bidirectional current I... write This process involves changing the magnetization state of the free layer to write data "0" or "1". A forward current controls the magnetization reversal of the free layer, writing data "1", while a reverse current clears the reversal state of the free layer, deleting data "1". Data reading is performed by applying current to the magnetic tunnel junction and then changing the reading current I... read The data stored within is determined by comparing it with a reference current. This method enables read / write separation, allowing reading and writing to be performed without the need for an external magnetic field. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a novel tilted magnetic tunnel junction storage device structure based on a Bi2Se3 / NiI2 heterojunction substrate according to the present invention.

[0016] Figure 2 Relationship between spin Hall conductivity and energy based on Bi2Se3 / NiI2 heterostructure;

[0017] Figure 3 Relationship between transmission coefficient and energy based on Bi2Se3 / NiI2 heterostructure;

[0018] Figure 4 The relationship between DOS and energy based on Bi2Se3 / NiI2 heterostructure. Detailed Implementation

[0019] To further illustrate the core idea of ​​the present invention, the following series of specific embodiments are given. However, the present invention is not limited to these specific embodiments. Any modifications made to the present invention by those skilled in the art will achieve similar results, and these modifications are also included in the present invention.

[0020] Example 1: A magnetic tunnel junction memory device based on a bismuth selenide and nickel iodide heterojunction substrate, comprising a top electrode, a SOT-MTJ, and a substrate arranged sequentially from top to bottom. The SOT-MTJ comprises a reference layer, a tunneling layer, a composite heavy metal layer, and a free layer arranged sequentially from top to bottom. The top electrode is made of aluminum with a thickness of 10 nm. The reference layer and the free layer are both made of CoFeB with a thickness of 2 nm, used to achieve magnetization reversal for data storage. The tunneling layer is made of MgO with a thickness of 2 nm, used to generate a tunneling effect to transmit spin signals. The heavy metal layer is formed by growing a tungsten thin layer on a tantalum thin layer to form a Ta / W composite material, which is placed between the tunneling layer and the free layer. Its thickness is 2nm. Since both Ta and W have large spin Hall angles, they are conducive to generating spin-orbit torque to flip the magnetic moment. The substrate is a Bi2Se3 / NiI2 heterojunction structure. The Bi2Se3 / NiI2 heterojunction has a relatively large spin Hall conductivity, which is suitable for the conversion of current and spin-orbit torque. In order to improve the conversion efficiency of current and spin-orbit torque, the thickness of the Bi2Se3 / NiI2 heterojunction is 9nm.

[0021] The data writing operation of the novel magnetic tunnel junction storage device is performed by injecting positive and negative currents I into the bottom electrode respectively. write This is done to change the magnetization state of the free layer, thereby enabling the writing of data 0 and 1; while the data reading operation is performed by transferring the read current I flowing through the SOT-MTJ. read The data stored therein is determined by comparing it with a reference current.

[0022] Example 2: A magnetic tunnel junction memory device based on a bismuth selenide and nickel iodide heterojunction substrate, comprising a top electrode, a SOT-MTJ, and a substrate arranged sequentially from top to bottom. The SOT-MTJ comprises a reference layer, a tunneling layer, a composite heavy metal layer, and a free layer arranged sequentially from top to bottom. The top electrode is made of copper with a thickness of 10 nm. The reference layer and the free layer are both made of CoFeB with a thickness of 2 nm, used to achieve magnetization reversal for data storage. The tunneling layer is made of MgO with a thickness of 2 nm, used to generate a tunneling effect to transmit spin signals. The heavy metal layer is formed by growing a tungsten thin layer on a tantalum thin layer to form a Ta / W composite material, which is placed between the tunneling layer and the free layer. Its thickness is 2nm. Since both Ta and W have large spin Hall angles, they are conducive to generating spin-orbit torque to flip the magnetic moment. The substrate is a Bi2Se3 / NiI2 heterojunction structure. The Bi2Se3 / NiI2 heterojunction has a relatively large spin Hall conductivity, which is suitable for the conversion of current and spin-orbit torque. In order to improve the conversion efficiency of current and spin-orbit torque, the thickness of the Bi2Se3 / NiI2 heterojunction is 9nm.

[0023] The data writing operation of the novel magnetic tunnel junction storage device is performed by injecting positive and negative currents I into the bottom electrode respectively. write This is done to change the magnetization state of the free layer, thereby enabling the writing of data 0 and 1; while the data reading operation is performed by transferring the read current I flowing through the SOT-MTJ. read The data stored in the SOT-MTJ is determined by comparing it with a reference current. The data is obtained by comparing the current flowing through the SOT-MTJ with the reference current.

[0024] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. 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 can be understood by those skilled in the art.

Claims

1. A magnetic tunnel junction memory device based on a bismuth selenide and nickel iodide heterojunction substrate, characterized in that: The magnetic tunnel junction memory device based on the bismuth selenide and nickel iodide heterojunction substrate comprises a top electrode, an SOT-MTJ and a substrate arranged in sequence from top to bottom, the SOT-MTJ comprises a reference layer, a tunneling layer, a composite heavy metal layer and a free layer arranged in sequence from top to bottom, the top electrode is made of aluminum or copper material, the reference layer and the free layer are both made of CoFeB material, the tunneling layer is made of MgO material, the composite heavy metal layer is made of Ta / W composite material formed by growing a tungsten thin layer on a tantalum thin layer, and the substrate is a Bi2Se3 and NiI2 heterojunction structure.

2. The magnetic tunnel junction storage device based on a heterojunction substrate of bismuth selenide and nickel iodide according to claim 1, wherein, The top electrode material is aluminum, and the thickness is 10 nm.

3. The magnetic tunnel junction storage device based on a heterojunction substrate of bismuth selenide and nickel iodide of claim 1, wherein, The reference layer and the free layer are CoFeB material, and the thickness is 2 nm, which is used for realizing magnetization reversal storage data.

4. The magnetic tunnel junction storage device based on a heterojunction substrate of bismuth selenide and nickel iodide of claim 1, wherein, The tunneling layer is made of MgO material, and the thickness is 2 nm, which is used for generating a tunneling effect to transmit a spin signal.

5. The magnetic tunnel junction storage device based on a heterojunction substrate of bismuth selenide and nickel iodide of claim 1, wherein: The composite heavy metal layer is Ta / W, which is arranged between the tunneling layer and the free layer, and the thickness is 2 nm, because Ta and W both have a large spin Hall angle, which is conducive to generating spin-orbit torque to reverse the magnetic moment.

6. The magnetic tunnel junction storage device based on a heterojunction substrate of bismuth selenide and nickel iodide of claim 1, wherein, The substrate is a Bi2Se3 / NiI2 heterojunction structure, the Bi2Se3 / NiI2 heterojunction has a relatively large spin Hall conductivity, which is suitable for the conversion of current and spin-orbit torque; in order to improve the conversion efficiency of current and spin-orbit torque, the thickness of the Bi2Se3 / NiI2 heterojunction is 9 nm.

7. The magnetic tunnel junction storage device based on a heterojunction substrate of bismuth selenide and nickel iodide of claim 1, wherein: The data write operation of the magnetic tunnel junction memory device is accomplished by injecting positive and negative currents I write to the bottom electrode respectively to change the magnetization state of the free layer, thereby realizing the writing and deleting of data 1; and the data read operation is accomplished by comparing the read current I read flowing through the SOT-MTJ with a reference current to determine the data information stored therein.

Images