Multi-ferroic tunnel junction device, spin valve device, and method of spin-polarized current modulation
By designing multiferroic tunnel junction devices and spin valve devices, the polarization direction of spin polarization current is controlled by the magnetoelectric coupling effect of the ferroelectric layer and the external electric field, thus solving the problem of high power consumption of spintronic devices and realizing low-power spin polarization current control and pure spin polarization current generation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- PEKING UNIV
- Filing Date
- 2022-07-29
- Publication Date
- 2026-07-31
AI Technical Summary
Existing spintronic devices, such as spin valves and magnetic tunnel junctions, suffer from high power consumption when controlling spin polarization current.
A multiferroic tunnel junction device is used to achieve magnetoelectric coupling effect through the ferroelectric layer between the first and second ferromagnetic layers. The polarization direction of the spin polarization current is controlled by changing the polarization state of the ferroelectric layer using an external electric field. The portion of the spin polarization current generated and detected is separated by a nonlocalized lateral structure.
The energy consumption of spin polarization current regulation was reduced, and the influence of static charge current was reduced by separating the generation and detection parts, thus achieving efficient regulation of pure spin polarization current.
Smart Images
Figure CN115332436B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of spintronics technology, and in particular to multiferroic tunnel junction devices, spin valve devices, and methods for controlling spin polarization current. Background Technology
[0002] Spintronics is an emerging field of electronics that primarily utilizes the spin property of electrons. It is a promising technology for developing alternative, multifunctional, high-speed, and low-power electronic devices. The main challenges in spintronics research include the generation and injection of spin-polarized current, and the manipulation and detection of spin direction. Currently, existing spintronic devices, such as spin valves and magnetic tunnel junctions, mostly use magnetic fields or large currents to manipulate the spin-polarized current, which leads to high power consumption. Summary of the Invention
[0003] This invention provides a multiferroic tunnel junction device, a spin valve device, and a method for controlling spin polarization current, in order to solve the problem of high power consumption required for controlling spin polarization current with a spin valve in the prior art.
[0004] This invention provides a multiferroic tunnel junction device, comprising a first ferromagnetic layer, a ferroelectric layer, and a second ferromagnetic layer stacked sequentially; wherein the first ferromagnetic layer and the second ferromagnetic layer are made of the same ferromagnetic metal material; the interfaces between the first ferromagnetic layer and the ferroelectric layer, and the interfaces between the second ferromagnetic layer and the ferroelectric layer, have symmetrical structures; the multiferroic tunnel junction device is used to generate and control spin polarization current through magnetoelectric coupling effect.
[0005] According to the present invention, a multiferroic tunnel junction device is provided, wherein the ferroelectric layer is made of an oxide or a two-dimensional ferroelectric material with ferroelectric properties; and the first ferromagnetic layer and the second ferromagnetic layer are made of ferromagnetic metal materials.
[0006] The present invention also provides a method for controlling spin polarization current. Using the above-mentioned multiferroic tunnel junction device, the method for controlling spin polarization current includes: applying a magnetic field or current to the first ferromagnetic layer and the second ferromagnetic layer to make the first ferromagnetic layer and the second ferromagnetic layer in an antiparallel magnetization state; removing the magnetic field or current applied to the first ferromagnetic layer and the second ferromagnetic layer to maintain the first ferromagnetic layer and the second ferromagnetic layer in an antiparallel magnetization state; applying a voltage between the first ferromagnetic layer and the second ferromagnetic layer to reverse the polarization state of the ferroelectric layer, thereby changing the spin tunneling barrier distribution of the multiferroic tunnel junction device and thus reversing the polarization direction of the spin current, thereby realizing the control of the generation of spin polarization current.
[0007] According to a method for controlling spin polarization current provided by the present invention, the polarization state of the spin tunneling current in a multiferroic tunnel junction device depends on the polarization state of the ferroelectric layer; changing the distribution of the spin tunneling barrier in the multiferroic tunnel junction device and thus reversing the polarization direction of the spin current includes: if the change in the polarization state of the ferroelectric layer makes the tunneling probability of spin polarization upward higher than that of spin polarization downward, the spin tunneling current is polarized upward; if the change in the polarization state of the ferroelectric layer makes the tunneling probability of spin polarization downward higher than that of spin polarization upward, the spin tunneling current is polarized downward.
[0008] The present invention also provides a spin valve device, comprising: a substrate; a metal layer disposed on the substrate; a first electrode disposed on one side of the metal layer; a first insulating layer disposed on the metal layer and on the same side as the first electrode; a first ferromagnetic layer disposed on the first insulating layer; a ferroelectric layer disposed on the first ferromagnetic layer; a second ferromagnetic layer disposed on the ferroelectric layer; a second electrode disposed on the other side of the metal layer; a second insulating layer disposed on the metal layer and on the same side as the second electrode; and a third ferromagnetic layer disposed on the second insulating layer; wherein the first ferromagnetic layer, the ferroelectric layer, and the second ferromagnetic layer constitute the above-described multiferroic tunnel junction device.
[0009] According to the present invention, a spin valve device is provided, wherein a first electrode, a first insulating layer and a multiferroic tunnel junction device are used to generate and regulate spin polarization current; a second electrode, a second insulating layer and a third ferromagnetic layer are used to detect spin polarization current.
[0010] According to a spin valve device provided by the present invention, the spin polarization current generated by the first electrode, the first insulating layer and the multiferroic tunnel junction device is injected into the metal layer through the first ferromagnetic layer and the first insulating layer. The injected pure spin polarization current is transported in the metal layer through the diffusion effect, and then injected into the third ferromagnetic layer through the second insulating layer. The strength and polarity of the generated pure spin polarization current are determined by measuring the magnitude and polarity of the voltage between the third ferromagnetic layer and the second electrode.
[0011] According to the present invention, a spin valve device is provided in which the first insulating layer and the second insulating layer are made of non-magnetic insulating materials, the first electrode and the second electrode are made of metallic materials, and the third ferromagnetic layer is made of magnetic metallic materials.
[0012] According to the present invention, in a spin valve device, the thickness of the second ferromagnetic layer is less than the spin diffusion length of the ferromagnetic metal material of the second ferromagnetic layer.
[0013] According to the present invention, the first ferromagnetic layer, the second ferromagnetic layer and the third ferromagnetic layer are made of iron (Fe), cobalt (Co) or nickel (Ni); the first insulating layer and the second insulating layer are made of magnesium oxide (MgO).
[0014] The multiferroic tunnel junction device, spin valve device, and spin polarization current control method provided by this invention are as follows: The multiferroic tunnel junction device is based on the magnetoelectric coupling effect generated at the interface between the ferromagnetic layer and the ferroelectric layer. By changing the polarization direction of the ferroelectric layer through an external electric field, the polarization direction of the spin current is controlled, which improves the speed of reversing the polarization state of the spin tunneling current and reduces the energy required to control the polarization state of the spin tunneling current. The spin valve adopts a non-localized lateral structure, which separates the part that generates and controls the spin current from the part that detects the spin current, thereby reducing the influence of electrostatic charge current and generating pure spin polarization current. Attached Figure Description
[0015] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0016] Figure 1 This is a schematic diagram of a structure of an embodiment of the multiferroic tunnel junction device of the present invention;
[0017] Figure 2 This is a schematic diagram of the multiferroic tunnel junction device model of the Co / HfO2 / Co structure of the present invention;
[0018] Figure 3(a) is the transmission function diagram of the Co / HfO2 / Co multiferroic tunnel junction device with Hf atoms as the interface;
[0019] Figure 3(b) is the transmission function diagram of the Co / HfO2 / Co multiferroic tunnel junction device with O atoms as the interface;
[0020] Figure 4 A schematic flowchart of an embodiment of the method for controlling spin polarization current;
[0021] Figure 5 This is a schematic diagram of the structure of an embodiment of the spin valve device of the present invention;
[0022] Figure 6 This is a schematic diagram illustrating the working principle of one embodiment of the spin valve device of the present invention. Detailed Implementation
[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0024] This invention provides a multiferroic tunnel junction device; please refer to [link / reference]. Figure 1 , Figure 1 This is a schematic diagram of a multiferroic tunnel junction device according to an embodiment of the present invention. In this embodiment, the multiferroic tunnel junction device includes a first ferromagnetic layer 110, a ferroelectric layer 120, and a second ferromagnetic layer 130 stacked sequentially.
[0025] The first ferromagnetic layer 110 and the second ferromagnetic layer 130 are made of the same ferromagnetic metal material;
[0026] The interfaces between the first ferromagnetic layer 110 and the ferroelectric layer 120, and between the second ferromagnetic layer 130 and the ferroelectric layer 120, have symmetrical structures. Multiferroic tunnel junction devices are used to generate and control spin-polarized currents through magnetoelectric coupling. Specifically, the height of the potential barrier of the controlled object is changed by altering the polarization state of the ferroelectric layer using an electric field, thereby reversing the polarization direction of the spin current.
[0027] In some embodiments, the ferroelectric layer 120 is made of an oxide or a two-dimensional ferroelectric material that has ferroelectric properties.
[0028] Alternatively, the ferromagnetic metallic material can be iron (Fe), cobalt (Co), or nickel (Ni), etc. The ferroelectric oxide can be HfO2; the two-dimensional ferroelectric material can be In2Se3, etc.
[0029] The multiferroic tunnel junction device in this embodiment uses the same ferromagnetic metal material and has a symmetrical interface. When the two ferromagnetic layers are in an antiparallel spin polarization state, an electric field is used to flip the polarization state of the ferroelectric layers. This changes the electron tunneling barrier height for different spin polarization orientations, thereby controlling the polarization state of the spin tunneling current. Using an electric field to change the polarization state of the ferroelectric layers allows for faster control of the spin tunneling current polarization direction and reduces the power consumption required to control the spin polarization current.
[0030] For example, a Co / HfO2 / Co multiferroic tunnel junction device with a symmetrical interface will be used as an example to illustrate the multiferroic tunnel junction device.
[0031] First-principles calculations show that when the first and second ferromagnetic layers are in an antiparallel magnetization state, the multiferroic tunnel junction has a magnetoelectric coupling effect, and the polarization state of the spin tunneling current can be controlled by changing the polarization state of the ferroelectric layer through an electric field.
[0032] The calculation model used in this embodiment is as follows: Figure 2 As shown, along the (001) crystal direction are 6 atomic layers of Co, 5 Hf atomic layers of HfO2, and 5 atomic layers of Co. Both ends of HfO2 are connected by Hf or O atoms, located at the vacancy of Co atoms, so that the two interface structures have symmetry.
[0033] To balance computational efficiency and accuracy, the model relaxation needs to be performed separately for both interfaces. After relaxation, the spacing between Hf or O atoms and Co atoms at the two interfaces is different; the spacing between the Hf atom interface at both ends and the Co atom is respectively... The distance between the O atom interface at both ends and the Co atom is Based on this, the transmission function of the device is calculated.
[0034] Figures 3(a) to (b) are transmission function diagrams of the Co / HfO2 / Co multiferroic tunnel junction device in Embodiment 1 of the present invention. Figure 3(a) is the transmission function diagram of the Co / HfO2 / Co multiferroic tunnel junction device with Hf atoms as the interface; Figure 3(b) is the transmission function diagram of the Co / HfO2 / Co multiferroic tunnel junction device with O atoms as the interface.
[0035] It can be seen that, with Hf as the interface and O as the interface, the change in the polarization state of the ferroelectric layer under antiparallel magnetization conditions causes changes in the barrier height for different spin polarization states. As shown in Figure 3(a), with Hf as the interface, at the Fermi level E... F Near 0, when the ferroelectric layer spin polarization is to the right, the probability of electron tunneling downwards is higher than that of electron tunneling upwards; when the ferroelectric layer spin polarization is to the left, the probability of electron tunneling upwards is higher than that of electron tunneling downwards.
[0036] As shown in Figure 3(b), when O is used as the interface, at the Fermi level E F Near 0, when the ferroelectric layer spin polarization is to the right, the probability of electron tunneling upward is higher than that of electron tunneling downward; when the ferroelectric layer spin polarization is to the left, the probability of electron tunneling downward is higher than that of electron tunneling upward, thus achieving electric field control of the spin current polarization current.
[0037] This embodiment demonstrates the feasibility of controlling the spin tunneling current polarization state by altering the polarization state of the ferroelectric layer through an electric field.
[0038] The above conclusions are based on an analysis of the Co / HfO2 / Co structure. However, the ferromagnetic layer material is not limited to Co; it can also be other ferromagnetic materials such as Fe and Ni. Similarly, the ferroelectric layer material is not limited to HfO2; it can also be other ferroelectric oxides or two-dimensional ferroelectric materials. The transport properties and spin polarization current of devices obtained using different materials will vary, requiring specific analysis based on the application of the device.
[0039] This invention also provides a method for controlling spin polarization current using the aforementioned multiferroic tunnel junction device. (See also...) Figure 4 , Figure 4A flowchart illustrating an embodiment of a method for controlling spin polarization current. In this embodiment, the method for controlling spin polarization current specifically includes steps S110 to S130, each step as follows:
[0040] S110: Apply a magnetic field or current to the first ferromagnetic layer and the second ferromagnetic layer to make the first ferromagnetic layer and the second ferromagnetic layer in an antiparallel magnetization state.
[0041] S120: Remove the magnetic field or current applied to the first ferromagnetic layer and the second ferromagnetic layer, so that the first ferromagnetic layer and the second ferromagnetic layer maintain an antiparallel magnetization state.
[0042] S130: Applying a voltage between the first and second ferromagnetic layers reverses the polarization state of the ferroelectric layer, changes the spin tunneling barrier distribution of the multiferroic tunnel junction device, and thus reverses the polarization direction of the spin current, thereby controlling the generation of spin polarization current.
[0043] In a multiferroic tunnel junction (MJT) device, the polarization state of the spin tunneling current depends on the polarization state of the ferroelectric layer. Therefore, the steps to change the spin tunneling barrier distribution in a MJT device and thus reverse the polarization direction of the spin current include:
[0044] If the change in the polarization state of the ferroelectric layer makes the tunneling probability of spin polarization upward higher than that of spin polarization downward, the spin tunneling current is polarized upward; if the change in the polarization state of the ferroelectric layer makes the tunneling probability of spin polarization downward higher than that of spin polarization upward, the spin tunneling current is polarized downward.
[0045] This invention also provides a spin valve device; please refer to [link / reference]. Figures 5-6 , Figure 5 This is a schematic diagram of a structure of an embodiment of the spin valve device of the present invention. Figure 6 This is a schematic diagram illustrating the working principle of one embodiment of the spin valve device of the present invention.
[0046] like Figure 5 As shown, the spin valve device may include a substrate 10, a metal layer 190, a first electrode 140, a first insulating layer 150, a first ferromagnetic layer 110, a ferroelectric layer 120, a second ferromagnetic layer 130, a second electrode 160, a second insulating layer 170, and a third ferromagnetic layer 180.
[0047] A metal layer 190 is disposed on a substrate 10; a first electrode 140 is disposed on one side of the metal layer 190; a first insulating layer 150 is disposed on the metal layer 190 and on the same side as the first electrode 140; a first ferromagnetic layer 110 is disposed on the first insulating layer 150; a ferroelectric layer 120 is disposed on the first ferromagnetic layer 110; a second ferromagnetic layer 130 is disposed on the ferroelectric layer 120; a second electrode 160 is disposed on the other side of the metal layer 190; a second insulating layer 170 is disposed on the metal layer 190 and on the same side as the second electrode 160; and a third ferromagnetic layer 180 is disposed on the second insulating layer 170.
[0048] The first ferromagnetic layer 110, the ferroelectric layer 120, and the second ferromagnetic layer 130 constitute the aforementioned multiferroic tunnel junction device. This device can generate and control the electric field of spin polarization current. By combining the aforementioned method of controlling polarization current in the spin valve device, fully electric control and detection of pure spin polarization current can be achieved.
[0049] The first electrode 140, the first insulating layer 150, and the multiferroic tunnel junction device are used to generate and regulate spin polarization current; the second electrode 160, the second insulating layer 170, and the third ferromagnetic layer 180 are used to detect spin polarization current.
[0050] The spin valve device is a lateral four-port device. Please refer to [link / reference]. Figure 6 The device as a whole includes a part that generates and regulates the spin polarization current and a part that detects the spin polarization current.
[0051] First electrode 140, first insulating layer 150 and multiferroic tunnel junction device ( Figure 6 The spin-polarized current generated (shown on the left) is injected into the metal layer 190 through the first ferromagnetic layer 110 and the first insulating layer 150. The injected pure spin-polarized current is transported in the metal layer 190 through the diffusion effect, and then injected into the third ferromagnetic layer 180 through the second insulating layer 170. The strength and polarity of the generated pure spin-polarized current are determined by measuring the magnitude and polarity of the voltage between the third ferromagnetic layer 180 and the second electrode 160.
[0052] Spin valve devices are used to generate and detect spin polarization current. Traditional spin valve devices mostly adopt a vertical structure, and the generated spin polarization current is affected by the net charge flow, resulting in a large background noise signal of the charge current, making it difficult to obtain a pure spin polarization current.
[0053] The spin valve in this embodiment adopts a non-localized lateral structure, which separates the part that generates and regulates the spin current from the part that detects the spin current, thereby reducing the influence of electrostatic charge current and generating pure spin polarization current.
[0054] Optionally, the thickness of the second ferromagnetic layer 130 is less than the spin diffusion length of the ferromagnetic metal material of the second ferromagnetic layer 130, so as to ensure that the spin polarization current is injected into the insulating layer and the first ferromagnetic layer 110 through diffusion.
[0055] In some embodiments, the first insulating layer 150 and the second insulating layer 170 are made of non-magnetic insulating materials, the first electrode 140 and the second electrode 160 are made of metallic materials, and the third ferromagnetic layer 180 is made of magnetic metallic materials.
[0056] Optionally, the first ferromagnetic layer 110, the second ferromagnetic layer 130 and the third ferromagnetic layer 180 are made of iron (Fe), cobalt (Co) or nickel (Ni); the first insulating layer 150 and the second insulating layer 170 are made of magnesium oxide (MgO) to improve the injection efficiency of spin polarization current.
[0057] For any aspects not described in detail in this invention, reference can be made to relevant prior art, such as device structure modeling and first-principles calculations.
[0058] The embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.
[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A spin valve device, characterized by, include: Substrate; A metal layer is disposed on the substrate; The first electrode is disposed on one side of the metal layer; A first insulating layer is disposed on the metal layer and on the same side as the first electrode; A first ferromagnetic layer is disposed on the first insulating layer; A ferroelectric layer is disposed on the first ferromagnetic layer; A second ferromagnetic layer is disposed on the ferroelectric layer; The second electrode is disposed on the other side of the metal layer; A second insulating layer is disposed on the metal layer and on the same side as the second electrode; A third ferromagnetic layer is disposed on the second insulating layer; The first ferromagnetic layer, the ferroelectric layer, and the second ferromagnetic layer constitute a multiferroic tunnel junction device; wherein the first ferromagnetic layer and the second ferromagnetic layer are made of the same ferromagnetic metal material; The interface between the first ferromagnetic layer and the ferroelectric layer, and the interface between the second ferromagnetic layer and the ferroelectric layer, have symmetrical structures; the multiferroic tunnel junction device is used to generate and control spin polarization current through magnetoelectric coupling effect.
2. The spin valve device of claim 1, wherein, The ferroelectric layer is made of ferroelectric oxide or two-dimensional ferroelectric material.
3. The spin valve device according to claim 1, characterized in that, The first electrode, the first insulating layer, and the multiferroic tunnel junction device are used to generate and modulate spin polarization current; the second electrode, the second insulating layer, and the third ferromagnetic layer are used to detect spin polarization current.
4. The spin valve device according to claim 3, characterized in that, The spin-polarized current generated by the first electrode, the first insulating layer, and the multiferroic tunnel junction device is injected into the metal layer through the first ferromagnetic layer and the first insulating layer. The injected pure spin-polarized current is transported in the metal layer through the diffusion effect, and then injected into the third ferromagnetic layer through the second insulating layer. The strength and polarity of the generated pure spin-polarized current are determined by measuring the magnitude and polarity of the voltage between the third ferromagnetic layer and the second electrode.
5. The spin valve device according to claim 1, characterized in that, The first and second insulating layers are made of non-magnetic insulating materials, and the first and second electrodes are made of metallic materials; the third ferromagnetic layer is made of magnetic metallic materials.
6. The spin valve device according to claim 1, characterized in that, The thickness of the second ferromagnetic layer is less than the spin diffusion length of the ferromagnetic metal material of the second ferromagnetic layer.
7. The spin valve device according to claim 5, characterized in that, The first ferromagnetic layer, the second ferromagnetic layer, and the third ferromagnetic layer are made of iron (Fe), cobalt (Co), or nickel (Ni); the first insulating layer and the second insulating layer are made of magnesium oxide (MgO).
8. A method for controlling spin-polarized current, characterized by, Using the spin valve device as described in any one of claims 1 to 7, the method for regulating the spin polarization current includes: A magnetic field or current is applied to the first ferromagnetic layer and the second ferromagnetic layer, so that the first ferromagnetic layer and the second ferromagnetic layer are in an antiparallel magnetization state; Remove the magnetic field or current applied to the first ferromagnetic layer and the second ferromagnetic layer, so that the first ferromagnetic layer and the second ferromagnetic layer maintain an antiparallel magnetization state; Applying a voltage between the first ferromagnetic layer and the second ferromagnetic layer reverses the polarization state of the ferroelectric layer, changes the spin tunneling barrier distribution of the multiferroic tunnel junction device, and thus reverses the polarization direction of the spin current, thereby controlling the generation of spin polarization current.
9. The method of claim 8, wherein the method further comprises: The polarization state of the spin tunneling current in the multiferroic tunnel junction device depends on the polarization state of the ferroelectric layer; changing the spin tunneling barrier distribution of the multiferroic tunnel junction device and thus reversing the polarization direction of the spin current includes: If the change in the polarization state of the ferroelectric layer causes the tunneling probability of spin polarization upward to be higher than that of spin polarization downward, the spin tunneling current will be polarized upward. If the change in the polarization state of the ferroelectric layer causes the tunneling probability of spin polarization downward to be higher than that of spin polarization upward, the spin tunneling current will be polarized downward.