A logic device based on electric field control of domain wall motion in multiferroic heterostructure

Abstract

The application discloses a logic device based on electric field control of magnetic domain wall movement in a multi-ferroelectric heterojunction, and belongs to the field of multi-ferroelectric heterojunctions and corresponding devices. The multi-ferroelectric heterojunction structure provided by the application can realize generation and movement of a magnetic domain wall in a magnetic nanowire by applying an external electric field between a substrate electrode layer and one of ferromagnetic electrodes, and under the coupling action between a piezoelectric substrate layer and a first / second ferromagnetic coupling area. By applying a positive voltage or grounding on the two ferromagnetic electrodes, input of two different logic states can be realized. Based on the two heterojunction structures, two logic devices are provided, a plurality of logic functions are realized by using only two logic input ends, the logic functions are reconfigurable, the switching of the logic functions can be realized, and the integration of the logic device is improved. In the process of large-scale integration, no current driving is involved, and the logic device has the characteristics of low power consumption.

Description

Technical Field

[0001] This invention belongs to the field of multiferroic heterojunctions and related devices, and more specifically, relates to a logic device based on electric field control of the movement of magnetic domain walls in a multiferroic heterojunction. Background Technology

[0002] Logic devices are commonly used in various logic function circuits required by electronic computers, and can also be integrated into logic chips to meet the digital needs of general systems. They can handle very complex control and computation problems. Furthermore, they can be used to implement in-memory computing, improving the processing power and speed of computers.

[0003] In the prior art, commonly used logic devices include logic devices based on the spin transfer torque (STT) or spin orbit torque (SOT) principle commonly used in the spin field, and CMOS-based logic devices commonly used in the semiconductor field.

[0004] In the field of spin computing, logic devices based on the principles of spin-transfer torque (STT) or spin-orbit torque (SOT) utilize spin as a state variable for information processing and transmission, both internally and at the logic gate level. These devices use the magnetization direction of nanomagnets to characterize and store information, and spin currents to transmit and process information. They offer advantages such as simple structure and high integration density. In the semiconductor field, CMOS-based logic devices are commonly used. They implement gate circuit functions through the combination and design of transistors. CMOS allows for extremely high logic integration density, small device size, and can be manufactured on a very small area. Furthermore, silicon-based processes are mature.

[0005] However, logic devices commonly used in the spin domain require large currents to achieve magnetization switching. During integration, device miniaturization leads to high current density and high power consumption. CMOS-based logic devices require multiple devices to implement various logic functions, and similarly suffer from high power consumption during integration. Furthermore, some existing logic devices have numerous inputs and complex structures when implementing multiple logic outputs; simultaneously, they cannot switch between logic functions, hindering large-scale device integration.

[0006] Ferroelectric / ferromagnetic heterostructures refer to the structures of ferromagnetic and ferroelectric composite multiferroic (FM / FE) heterojunction thin films. In the prior art, such multiferroic heterojunction structures can be used as connecting components for logic units to realize the construction of large and complex logic networks. However, large and complex logic networks constructed using this commonly used multiferroic heterojunction structure cannot control the input states of intermediate logic units, which causes many inconveniences in the construction of large and complex logic networks. Summary of the Invention

[0007] To address the shortcomings and improvement needs of existing technologies, this invention provides a low-power logic device based on electric field control of the magnetic domain wall motion in a multiferroic heterojunction. The purpose is to design a new multiferroic heterojunction structure that enables control of the input state of intermediate logic units in large and complex logic networks, and to design a new logic device based on this multiferroic heterojunction structure, thereby simultaneously reducing the power consumption of the logic device and improving its integration density.

[0008] To achieve the above objectives, according to one aspect of the present invention, a multiferroic heterojunction structure is provided, comprising: a substrate electrode layer, a piezoelectric substrate layer, a ferromagnetic thin film layer, a first ferromagnetic electrode, and a second ferromagnetic electrode;

[0009] The substrate electrode layer is disposed on the piezoelectric substrate layer;

[0010] The ferromagnetic thin film layer includes a first ferromagnetic coupling region, a second ferromagnetic coupling region, and ferromagnetic nanowires connecting the two ferromagnetic coupling regions; the first ferromagnetic coupling region and the second ferromagnetic coupling region are disposed on other surfaces of the piezoelectric substrate layer, and the other surfaces correspond to the surfaces of the substrate electrode layer disposed on the piezoelectric substrate layer.

[0011] The first ferromagnetic electrode covers the first ferromagnetic coupling region, and the second ferromagnetic electrode covers the second ferromagnetic coupling region.

[0012] The ferromagnetic nanowire serves as the active region. A voltage is applied between the substrate electrode layer and the ferromagnetic electrode to generate an electric field at both ends of the piezoelectric substrate layer. Under the coupling effect between the piezoelectric substrate layer and the ferromagnetic coupling region, the generation and movement of magnetic domains in the ferromagnetic nanowire are controlled. The ferromagnetic electrode is either a first ferromagnetic electrode or a second ferromagnetic electrode, and the ferromagnetic coupling region is either a first ferromagnetic coupling region or a second ferromagnetic coupling region.

[0013] Furthermore, the substrate electrode layer is disposed on one surface of the piezoelectric substrate layer, and the first ferromagnetic coupling region and the second ferromagnetic coupling region are disposed on the other surface of the piezoelectric substrate layer corresponding to the substrate electrode layer.

[0014] Further, the substrate electrode layer includes a first substrate electrode layer and a second substrate electrode layer, the first substrate electrode layer and the second substrate electrode layer are respectively disposed on two adjacent surfaces of the piezoelectric substrate layer; the ferromagnetic thin film layer is disposed on the other two surfaces of the piezoelectric substrate layer corresponding to the first substrate electrode layer and the second substrate electrode layer, and the other two surfaces are referred to as the first side surface and the second side surface, respectively.

[0015] The first ferromagnetic coupling region is located on the first side of the piezoelectric substrate, and the second ferromagnetic coupling region is located on the second side of the piezoelectric substrate.

[0016] Furthermore, the ferromagnetic nanowires located on the first and second sides of the piezoelectric substrate are of equal length.

[0017] Furthermore, the ferromagnetic thin film layer is prepared into a dumbbell shape by photolithography. The two ends of the dumbbell shape are the first ferromagnetic coupling region and the second ferromagnetic coupling region, and the middle region of the dumbbell shape is a ferromagnetic nanowire.

[0018] Furthermore, the piezoelectric substrate layer is made of lead magnesium niobate-lead titanate, and the ferromagnetic thin film layer is made of Ni.

[0019] According to a second aspect of the present invention, a logic device for controlling the movement of magnetic domain walls in a multiferroic heterojunction is provided, comprising: a multiferroic heterojunction structure, a tunneling layer, and a fixing layer disposed on the tunneling layer; wherein the multiferroic heterojunction structure is the multiferroic heterojunction structure described in the first aspect;

[0020] The tunneling layer is disposed above the ferromagnetic nanowire. The ferromagnetic nanowire, the tunneling layer, and the fixing layer form a magnetic tunnel junction structure from bottom to top, which serves as the output terminal of the logic device. The first ferromagnetic electrode and the second ferromagnetic electrode serve as the two input terminals of the logic device.

[0021] Furthermore, the magnetization direction of the fixed layer is controlled to be along the +x axis, so that the logic device can perform XOR logic operation;

[0022] The magnetization direction of the fixed layer is controlled to be along the -x axis, so that the logic device can perform XOR logic operation;

[0023] Here, the direction parallel or antiparallel to the ferromagnetic nanowire is defined as the +x axis direction, and applying a positive voltage to the first or second ferromagnetic electrode is defined as logic input "1", while grounding the first or second ferromagnetic electrode is defined as logic input "0".

[0024] According to a third aspect of the present invention, a logic device for controlling the movement of magnetic domain walls in a multiferroic heterojunction is provided, comprising a multiferroic heterojunction structure, a first tunneling layer, a second tunneling layer, a first fixing layer, and a second fixing layer; wherein the multiferroic heterojunction is the multiferroic heterojunction structure described in the first aspect;

[0025] The first tunneling layer is disposed above the ferromagnetic nanowires located on the first side of the piezoelectric substrate, and the first fixing layer is disposed on the first tunneling layer. The ferromagnetic nanowires, the first tunneling layer, and the first fixing layer on the first side of the piezoelectric substrate form a first magnetic tunnel junction structure from bottom to top.

[0026] The second tunneling layer is disposed above the ferromagnetic nanowires located on the second side of the piezoelectric substrate, and the second fixing layer is disposed on the second tunneling layer. The ferromagnetic nanowires located on the second side of the piezoelectric substrate, the second tunneling layer, and the second fixing layer form a second magnetic tunnel junction structure from bottom to top.

[0027] The first ferromagnetic electrode and the second ferromagnetic electrode serve as the two logic input terminals of the logic device, and the first magnetic tunnel junction structure and the second magnetic tunnel junction structure are connected in parallel to serve as the output terminal of the logic device.

[0028] Furthermore, the magnetization direction of the first fixed layer is controlled to be along the +z axis and the magnetization direction of the second fixed layer is controlled to be along the -y axis, so that the logic device can perform OR logic operations;

[0029] The magnetization direction of the first fixed layer is controlled to be along the -z axis and the magnetization direction of the second fixed layer is controlled to be along the +y axis, so that the logic device can perform AND and NOT logic operations;

[0030] Here, the direction parallel or antiparallel to the ferromagnetic nanowires located on the first side of the piezoelectric substrate is defined as the +z axis direction, and the direction parallel or antiparallel to the ferromagnetic nanowires located on the second side of the piezoelectric substrate is defined as the +y axis direction; applying a positive voltage to the first or second ferromagnetic electrode is defined as logic input "1", and grounding the first or second ferromagnetic electrode is defined as logic input "0".

[0031] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0032] (1) The multiferroic heterojunction structure provided by the present invention can generate and move magnetic domain walls in magnetic nanowires by applying an external electric field between the substrate electrode layer and one of the ferromagnetic electrodes and under the coupling effect between the piezoelectric substrate layer and the first / second ferromagnetic coupling region. By applying a positive voltage or grounding on the two ferromagnetic electrodes, two different logic states can be realized as inputs. It can be used as two logic input terminals of logic devices. In the process of constructing large and complex logic networks, it can realize the control of the input state of intermediate logic units.

[0033] (2) Based on two multiferroic heterojunction structures, the present invention also designs corresponding logic devices. The logic devices are logic devices based on electric field control of the magnetic domain wall movement in the multiferroic heterojunction. By controlling the electric field of the piezoelectric substrate, the magnetization direction of the fixed layer can be controlled to be parallel or antiparallel to the final magnetization direction in the ferromagnetic nanowire. According to the input logic state, the state of the magnetic tunnel junction can be read to obtain different output logic states. The present invention uses only two logic input terminals to realize several basic and necessary logic functions in Boolean logic, which can improve the integration of logic devices. Moreover, in the process of large-scale integration, since no current drive is involved, it has the characteristics of low power consumption.

[0034] More importantly, the logic device designed in this invention has reconfigurable logic functions. By controlling the magnetization direction of the fixed layer, the logic functions can be switched. This innovative design can transfer the process complexity of the fabrication structure to the circuit design, which greatly improves the integrability of the device. Attached Figure Description

[0035] Figure 1 This is the planar multiferroic heterostructure provided in Embodiment 1 of the present invention.

[0036] Figure 2 This is a schematic diagram of a logic device structure based on a planar multiferroic heterojunction provided in Embodiment 2 of the present invention.

[0037] Figure 3 The logic operation process of the logic device provided in Embodiment 2 of the present invention.

[0038] Figure 4 The diagram shows the planar multiferroic heterojunction structure and the corresponding logic device structure provided in embodiments 3 and 4 of the present invention.

[0039] Figure 5 The logic operation process of the logic device provided in Embodiment 4 of the present invention.

[0040] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0041] 1 is the substrate electrode layer, 2 is the piezoelectric substrate layer, 301 is the first ferromagnetic coupling region, 304 is the second ferromagnetic coupling region, 302 is the ferromagnetic nanowire, 401 is the first ferromagnetic electrode, 402 is the second ferromagnetic electrode, 5 is the tunneling layer, 6 is the fixing layer, 7 is the word line, 101 is the first substrate electrode layer, 102 is the second substrate electrode layer, 501 is the first tunneling layer, 502 is the second tunneling layer, 601 is the first fixing layer, and 602 is the second fixing layer. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0043] In this invention, the terms "first," "second," etc., used in the invention and accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0044] The present invention provides a multiferroic heterojunction structure, comprising: a substrate electrode layer, a piezoelectric substrate layer 2, a ferromagnetic thin film layer, a first ferromagnetic electrode 401 and a second ferromagnetic electrode 402;

[0045] The substrate electrode layer is disposed on the piezoelectric substrate layer 2;

[0046] The ferromagnetic thin film layer includes a first ferromagnetic coupling region 301, a second ferromagnetic coupling region 304, and a ferromagnetic nanowire 302 connecting the two ferromagnetic coupling regions; the first ferromagnetic coupling region 301 and the second ferromagnetic coupling region 304 are disposed on other surfaces of the piezoelectric substrate layer 2, which correspond to the surfaces of the substrate electrode layer disposed on the piezoelectric substrate layer 2.

[0047] The first ferromagnetic electrode 401 covers the first ferromagnetic coupling region 301, and the second ferromagnetic electrode 402 covers the second ferromagnetic coupling region 304.

[0048] Ferromagnetic nanowires serve as active regions. A voltage is applied between the substrate electrode layer and the ferromagnetic electrode to generate an electric field at both ends of the piezoelectric substrate layer. Under the coupling effect between the piezoelectric substrate layer and the ferromagnetic coupling region, the generation and movement of magnetic domains in the ferromagnetic nanowires are controlled. The ferromagnetic electrode is either a first ferromagnetic electrode or a second ferromagnetic electrode, and the ferromagnetic coupling region is either a first ferromagnetic coupling region or a second ferromagnetic coupling region.

[0049] In this embodiment, the substrate electrode layer is disposed on one or two adjacent surfaces of the piezoelectric substrate layer 2. When the substrate electrode layer is disposed on one surface of the piezoelectric substrate layer 2, the resulting heterojunction structure is a planar heterojunction structure. When the substrate electrode layer is disposed on two adjacent surfaces of the piezoelectric substrate layer 2, the resulting heterojunction structure is a double-ended heterojunction structure. The planar heterojunction structure and the double-ended heterojunction structure will be described below with reference to Embodiment 1 and Embodiment 3, respectively. The logic device formed based on the planar heterojunction structure and the logic device formed based on the double-ended heterojunction structure will be described with reference to Embodiment 2 and Embodiment 4.

[0050] Example 1

[0051] like Figure 1As shown, an embodiment of the present invention provides a planar multiferroic heterojunction structure, comprising: a substrate electrode layer 1, a piezoelectric substrate layer 2, a ferromagnetic thin film layer, and two ferromagnetic electrodes.

[0052] The substrate electrode layer 1 is disposed on one side of the piezoelectric substrate layer 2, and the ferromagnetic thin film layer is disposed on the other side of the piezoelectric substrate layer 2. The two sides are relative to each other; that is, the ferromagnetic thin film layer is disposed on the other side of the piezoelectric substrate layer 2 corresponding to the substrate electrode layer 1.

[0053] The ferromagnetic thin film layer includes two ferromagnetic coupling regions and ferromagnetic nanowires 302, with the two ferromagnetic coupling regions connected by the ferromagnetic nanowires 302; the two ferromagnetic coupling regions are referred to as the first ferromagnetic coupling region 301 and the second ferromagnetic coupling region 304.

[0054] Two ferromagnetic electrodes are respectively covered on two ferromagnetic coupling regions, and the two ferromagnetic electrodes are referred to as the first ferromagnetic electrode 401 and the second ferromagnetic electrode 402. The first ferromagnetic electrode 401 is covered on the first ferromagnetic coupling region 301, and the second ferromagnetic electrode 402 is covered on the second ferromagnetic coupling region 304. In the ferromagnetic thin film layer, the ferromagnetic nanowire 302 without electrode coverage in the middle serves as an active region. Under the action of the electric field at both ends of the piezoelectric substrate layer, it generates magnetic domains and controls the movement of the magnetic domains.

[0055] Preferably, the areas of the two ferromagnetic coupling regions 301 and 304 are larger than the area of ​​the ferromagnetic nanowire 302, which facilitates electrode coverage. In this embodiment, the ferromagnetic thin film layer is prepared into a dumbbell shape by photolithography, with the two ends of the dumbbell shape being the two ferromagnetic coupling regions and the middle region being the ferromagnetic nanowire.

[0056] Preferably, the piezoelectric substrate layer can be made of materials with high piezoelectric sensitivity, such as lead magnesium niobate-lead titanate (PMN-PT), and the ferromagnetic thin film layer can be made of materials with high magnetoelasticity, such as Ni.

[0057] An external electric field is applied between the substrate electrode layer 1 and a ferromagnetic electrode, generating an electric field at both ends of the piezoelectric substrate layer. Taking the application of an external electric field between the substrate electrode layer 1 and the second ferromagnetic electrode 402 as an example, the second ferromagnetic electrode 402 is grounded, and the substrate electrode layer 1 is connected to a positive voltage. Under the action of the electric field at both ends of the piezoelectric substrate layer 2, stress is generated inside the piezoelectric material. This stress is transmitted to the second ferromagnetic coupling region 304 through the coupling between the piezoelectric substrate layer and the second ferromagnetic coupling region 304. The strain inside the second ferromagnetic coupling region 304 induces an easy magnetization axis along the longitudinal direction of the ferromagnetic nanowire 302, and magnetic domains are generated inside the ferromagnetic nanowire 302. Due to the non-uniform distribution of strain, the magnetic moment of the domain walls in the magnetic nanowires 302 near the second ferromagnetic coupling region 304, which is closer to the applied voltage end, is greater than that in the magnetic nanowires 302 near the first ferromagnetic coupling region 301, which is farther from the applied voltage end. Therefore, in the magnetic nanowires 302 near the second ferromagnetic coupling region 304, the incompletely reversed magnetic domains generated by the precession of the magnetic moment form 180° reversed magnetic domains under the action of a vertically downward electric field. Stable Nell-type domain walls are formed between the domains, and the domain walls in the magnetic nanowires 302 near the first ferromagnetic coupling region 301 move towards the other end at a stable speed under the action of the electric field. If an external electric field is applied between the substrate electrode layer 1 and the first ferromagnetic electrode 401, with the first ferromagnetic electrode 401 grounded and the substrate electrode layer 1 connected to a positive voltage, the magnetic domain walls in the magnetic nanowires 302 near the second ferromagnetic coupling region 304 move towards the other end at a stable speed under the action of the electric field through the coupling between the piezoelectric substrate layer and the first ferromagnetic coupling region 301.

[0058] Example 2

[0059] like Figure 2 As shown, based on the planar multiferroic heterojunction structure provided in Embodiment 1, the present invention provides a logic device for controlling the movement of magnetic domain walls in a multiferroic heterojunction, including the planar multiferroic heterojunction structure and a semi-magnetic tunnel junction structure of Embodiment 1. The semi-magnetic tunnel junction structure includes a tunneling layer 5 and a fixing layer 6 disposed on the tunneling layer 5. The tunneling layer 5 is disposed directly above the ferromagnetic nanowire 302 of the planar multiferroic heterojunction structure. The first ferromagnetic electrode 401 and the second ferromagnetic electrode 402 serve as the two logic input terminals of the logic device. The ferromagnetic nanowire 302, the tunneling layer 5, and the fixing layer 6 form a magnetic tunnel junction structure from bottom to top, which serves as the output terminal of the logic device.

[0060] Specifically, during the device integration process, word lines 7 are also provided on the fixed layer 6, which are used to lead out the magnetization state of the fixed layer 6.

[0061] As a preferred option, the fixing layer material can be cobalt iron boron, cobalt iron, or other similar materials.

[0062] Similarly, taking the application of an external electric field between the substrate electrode layer 1 and the second ferromagnetic electrode 402 as an example, under the action of the electric field at both ends of the piezoelectric substrate layer, stress is generated inside the piezoelectric material. This stress can control the generation and movement of magnetic domains in the ferromagnetic nanowire 302 through the coupling effect between the piezoelectric substrate layer and the second ferromagnetic coupling region 304.

[0063] In this embodiment, the first ferromagnetic electrode 401 is used as the logic input A of the logic device, and the second ferromagnetic electrode 402 is used as the logic input B of the logic device. Applying a positive voltage to the first ferromagnetic electrode 401 or the second ferromagnetic electrode 402 is recorded as logic input "1", and grounding the first ferromagnetic electrode 401 or the second ferromagnetic electrode 402 is recorded as logic input "0". AB represents the input logic state of the logic device in this embodiment of the invention, wherein the substrate electrode layer 1 is always connected to a positive voltage. In this embodiment, the positive voltage applied to the first ferromagnetic electrode 401 or the second ferromagnetic electrode 402 is 400V.

[0064] like Figure 3 As shown, based on the logic device provided in this embodiment, the control method for the logic device provided in this embodiment of the invention is as follows:

[0065] When the magnetization direction of the fixed layer 6 is along the +x axis, and the logic states A and B of the logic device inputs are "00" (i.e., both the first ferromagnetic electrode 401 and the second ferromagnetic electrode 402 are grounded), the final magnetization direction in the ferromagnetic nanowire 302 is along the +x axis, parallel to the magnetization direction of the fixed layer. The ferromagnetic nanowire 302, tunneling layer 5, and fixed layer 6 form a magnetic tunnel junction in a low-resistance state, at which point the logic output state is "0". The direction parallel or antiparallel to the ferromagnetic nanowire 302 is defined as the +x axis.

[0066] When the logic states A and B at the input terminals of the logic device are "10" respectively, that is, the first ferromagnetic electrode 401 is connected to a positive voltage, the second ferromagnetic electrode 402 is grounded, the final magnetization direction in the ferromagnetic nanowire 302 is antiparallel to the magnetization direction of the fixed layer, and the ferromagnetic nanowire 302, the tunneling layer 5 and the fixed layer 6 form a magnetic tunnel junction in a high-resistivity state. At this time, the logic output state is "1".

[0067] When the logic states A and B at the input terminals of the logic device are "0" and "1" respectively, that is, the first ferromagnetic electrode 401 is grounded, the second ferromagnetic electrode 402 is connected to a high voltage, the final magnetization direction in the ferromagnetic nanowire 302 is antiparallel to the magnetization direction of the fixed layer, and the ferromagnetic nanowire 302, the tunneling layer 5 and the fixed layer 6 form a magnetic tunnel junction in a high-resistivity state. At this time, the logic output state is "1".

[0068] When the logic states A and B at the input terminals of the logic device are "11" respectively, that is, the first ferromagnetic electrode 401 is connected to a high voltage and the second ferromagnetic electrode 402 is connected to a high voltage. The final magnetization direction in the ferromagnetic nanowire 302 is parallel to the magnetization direction of the fixed layer. The ferromagnetic nanowire 302, the tunneling layer 5 and the fixed layer 6 form a magnetic tunnel junction in a low-resistance state. At this time, the logic output state is "0".

[0069] The above logic devices implement XOR logic operations.

[0070] When the magnetization direction of the fixed layer 6 is along the -x axis and the logic states A and B of the input terminals of the logic device are "00" (i.e., the first ferromagnetic electrode 401 and the second ferromagnetic electrode 402 are both grounded), the final magnetization direction in the ferromagnetic nanowire 302 is along the +x axis, which is antiparallel to the magnetization direction of the fixed layer. The ferromagnetic nanowire 302, the tunneling layer 5 and the fixed layer 6 form a magnetic tunnel junction in a high-resistivity state. At this time, the logic output state is "1".

[0071] When the logic states A and B at the input terminals of the logic device are "10" respectively, that is, the first ferromagnetic electrode 401 is connected to a positive voltage and the second ferromagnetic electrode 402 is grounded, the final magnetization direction in the ferromagnetic nanowire 302 is parallel to the magnetization direction of the fixed layer. The ferromagnetic nanowire 302, the tunneling layer 5 and the fixed layer 6 form a magnetic tunnel junction in a low-resistance state. At this time, the logic output state is "0".

[0072] When the logic states A and B at the input terminals of the logic device are "0" and "1" respectively, that is, the first ferromagnetic electrode 401 is grounded and the second ferromagnetic electrode 402 is connected to a high voltage, the final magnetization direction in the ferromagnetic nanowire 302 is parallel to the magnetization direction of the fixed layer. The ferromagnetic nanowire 302, the tunneling layer 5 and the fixed layer 6 form a magnetic tunnel junction in a low-resistance state. At this time, the logic output state is "0".

[0073] When the logic states A and B at the input terminals of the logic device are "11" respectively, that is, the first ferromagnetic electrode 401 is connected to a high voltage and the second ferromagnetic electrode 402 is connected to a high voltage, the final magnetization direction in the ferromagnetic nanowire 302 is antiparallel to the magnetization direction of the fixed layer. The ferromagnetic nanowire 302, the tunneling layer 5 and the fixed layer 6 form a magnetic tunnel junction in a high-resistivity state. At this time, the logic output state is "1".

[0074] The above logic devices implement the XOR logic operation.

[0075] The truth tables for the XOR and XNOR logic operations implemented by the above logic devices are shown in Table 1 below:

[0076] Table 1 Truth table corresponding to the logic devices provided in this embodiment.

[0077]

[0078] In other words, the alignment of the magnetization direction of the fixed layer 6 with the final magnetization direction in the ferromagnetic nanowire 302, whether parallel or antiparallel, directly determines the low / high resistance state of the magnetic tunnel junction. By applying a read current, the magnetoresistance change of the magnetic tunnel junction can be read, thereby determining the magnetization state change of the ferromagnetic nanowire in the region below the tunneling layer. In other words, different output logic states can be obtained based on the input logic state, and the XOR and XNOR operations of the logic device can be implemented using only two logic input terminals.

[0079] Example 3

[0080] like Figure 4 As shown, unlike Embodiment 1, this embodiment provides a double-end multi-iron heterojunction structure, and the substrate electrode layer includes a first substrate electrode layer 101 and a second substrate electrode layer 102.

[0081] The first substrate electrode layer 101 and the second substrate electrode layer 102 are respectively disposed on two adjacent surfaces of the piezoelectric substrate layer 2, and the ferromagnetic thin film layer is disposed on the other two surfaces of the piezoelectric substrate layer 2 corresponding to the first substrate electrode layer 101 and the second substrate electrode layer 102. These other two surfaces are referred to as the first side surface and the second side surface, respectively.

[0082] The ferromagnetic thin film layer includes a first ferromagnetic coupling region 301, a second ferromagnetic coupling region 304, and ferromagnetic nanowires 302 connecting the first ferromagnetic coupling region 301 and the second ferromagnetic coupling region 304. The first ferromagnetic coupling region 301 is located on a first side surface of the piezoelectric substrate layer 2 corresponding to the first substrate electrode layer 101, and the second ferromagnetic coupling region 304 is located on a second side surface of the piezoelectric substrate layer 2 corresponding to the second substrate electrode layer 102. Correspondingly, the ferromagnetic nanowires 302 connecting the first ferromagnetic coupling region 301 and the second ferromagnetic coupling region 304 are also located on the first side surface and the second side surface of the piezoelectric substrate layer 2, respectively.

[0083] The first ferromagnetic electrode 401 covers the first ferromagnetic coupling region 301, and the second ferromagnetic electrode 402 covers the second ferromagnetic coupling region 304.

[0084] Preferably, the ferromagnetic nanowires 302 on the two sides of the piezoelectric substrate 2 are of equal length.

[0085] Preferably, the ferromagnetic thin film layer is covered on the first and second sides of the piezoelectric substrate layer 2 by a semiconductor fabrication process.

[0086] Similar to Example 1, when an electric field is applied to the piezoelectric substrate 2, a corresponding voltage is applied between the first substrate electrode layer 101 and the first ferromagnetic electrode 401, with the first substrate electrode layer 101 grounded and the first ferromagnetic electrode 401 positively charged; or a corresponding voltage is applied between the second substrate electrode layer 102 and the second ferromagnetic electrode 402, with the second substrate electrode layer 102 grounded and the second ferromagnetic electrode 402 positively charged. In both cases, the electric field at both ends of the piezoelectric substrate layer will cause stress to be generated inside it. This stress can control the generation and movement of magnetic domain walls in the ferromagnetic nanowire 302 through coupling.

[0087] Example 4

[0088] like Figure 4 As shown, based on the double-ended multiferroic heterojunction structure provided in Embodiment 3, this embodiment provides a logic device based on the double-ended multiferroic heterojunction structure in Embodiment 3. The logic device includes: the double-ended multiferroic heterojunction structure in Embodiment 3, a first tunneling layer 501, a second tunneling layer 502, a first fixing layer 601, and a second fixing layer 602.

[0089] The first tunneling layer 501 is disposed directly above the ferromagnetic nanowire 302 located on the first side of the piezoelectric substrate layer 2, and the first fixing layer 601 is disposed on the first tunneling layer 501. The ferromagnetic nanowire 302, the first tunneling layer 501 and the first fixing layer 601 located on the first side of the piezoelectric substrate layer 2 form a magnetic tunnel junction structure from bottom to top, which is referred to as the first magnetic tunnel junction structure.

[0090] The second tunneling layer 502 is disposed directly above the ferromagnetic nanowire 302 located on the second side of the piezoelectric substrate layer 2, and the second fixing layer 602 is disposed on the second tunneling layer 502. The ferromagnetic nanowire 302, the second tunneling layer 502 and the second fixing layer 602 located on the second side of the piezoelectric substrate layer 2 form a magnetic tunnel junction structure from bottom to top, which is referred to as the second magnetic tunnel junction structure.

[0091] The first ferromagnetic electrode 401 and the second ferromagnetic electrode 402 serve as the two logic input terminals of the dual-ended logic device, and the first magnetic tunnel junction structure and the second magnetic tunnel junction structure are connected in parallel to serve as the output terminal of the dual-ended logic device.

[0092] Similar to Embodiment 2, let the first ferromagnetic electrode 401 be the logic input A of the logic device, and the second ferromagnetic electrode 402 be the logic input B of the logic device. Applying a positive voltage to the first ferromagnetic electrode 401 or the second ferromagnetic electrode 402 is recorded as logic input "1", and grounding the first ferromagnetic electrode 401 or the second ferromagnetic electrode 402 is recorded as logic input "0". AB is the logic state of the input terminal of the logic device in the embodiment of the present invention, wherein the first substrate electrode layer 101 and the second substrate electrode layer 102 are always connected to a positive voltage.

[0093] like Figure 5 As shown, based on the logic device provided in this embodiment, the control method for the logic device provided in this embodiment of the invention is as follows:

[0094] When the magnetization direction of the first fixed layer 501 is controlled to be along the +z axis and the magnetization direction of the second fixed layer 502 is controlled to be along the -y axis, and the logic states A and B of the input terminals of the logic device are "00" (i.e., both the first ferromagnetic electrode 401 and the second ferromagnetic electrode 402 are grounded), the final magnetization direction of the ferromagnetic nanowires located on the first side of the piezoelectric substrate 2 is along the +z axis, and the final magnetization direction of the ferromagnetic nanowires located on the second side of the piezoelectric substrate 2 is along the -y axis. That is, the final magnetization direction of the ferromagnetic nanowires located on the first and second sides of the piezoelectric substrate 2 is parallel to the magnetization direction of the corresponding first and second fixed layers. After the first magnetic tunnel junction and the second magnetic tunnel junction are connected in parallel, they are in a low-resistance state. At this time, the logic output state is "0". Among them, the direction parallel or antiparallel to the ferromagnetic nanowires located on the first side of the piezoelectric substrate is set as the +z axis, and the direction parallel or antiparallel to the ferromagnetic nanowires located on the second side of the piezoelectric substrate is set as the +y axis.

[0095] When the first ferromagnetic electrode 401 is connected to a positive voltage and the second ferromagnetic electrode 402 is grounded, the logic states A and B at the input terminals of the logic device are "10" respectively. The final magnetization direction of the ferromagnetic nanowires located on the first side of the piezoelectric substrate layer 2 is parallel to the magnetization direction of the corresponding first fixed layer, and the final magnetization direction of the ferromagnetic nanowires located on the second side of the piezoelectric substrate layer 2 is antiparallel to the magnetization direction of the corresponding second fixed layer. The first magnetic tunnel junction and the second magnetic tunnel junction are connected in parallel to form a high-impedance state. At this time, the logic output state is "1".

[0096] When the first ferromagnetic electrode 401 is grounded and the second ferromagnetic electrode 402 is connected to a positive voltage, the logic states A and B at the input terminals of the logic device are "0" and "1" respectively. The final magnetization direction of the ferromagnetic nanowires located on the first side of the piezoelectric substrate layer 2 is antiparallel to the magnetization direction of the corresponding first fixed layer, and the final magnetization direction of the ferromagnetic nanowires located on the second side of the piezoelectric substrate layer 2 is parallel to the magnetization direction of the corresponding second fixed layer. The first magnetic tunnel junction and the second magnetic tunnel junction are connected in parallel to form a high-impedance state. At this time, the logic output state is "1".

[0097] When the first ferromagnetic electrode 401 and the second ferromagnetic electrode 402 are both connected to a positive voltage, the logic states A and B at the input terminals of the logic device are "11" respectively. The final magnetization direction of the ferromagnetic nanowires located on the first side of the piezoelectric substrate layer 2 is antiparallel to the magnetization direction of the corresponding first fixed layer. The final magnetization direction of the ferromagnetic nanowires located on the second side of the piezoelectric substrate layer 2 is antiparallel to the magnetization direction of the corresponding second fixed layer. The first magnetic tunnel junction and the second magnetic tunnel junction are connected in parallel to form a high-impedance state. At this time, the logic output state is "1".

[0098] The above logic devices implement OR logic operations.

[0099] When the magnetization direction of the first fixed layer 501 is controlled to be along the -z axis and the magnetization direction of the second fixed layer 502 is controlled to be along the +y axis, and the logic states A and B of the input terminals of the logic device are "00" (i.e., both the first ferromagnetic electrode 401 and the second ferromagnetic electrode 402 are grounded), the final magnetization direction of the ferromagnetic nanowires located on the first side of the piezoelectric substrate layer 2 is along the +z axis, and the final magnetization direction of the ferromagnetic nanowires located on the second side of the piezoelectric substrate layer 2 is along the -y axis. That is, the final magnetization directions of the ferromagnetic nanowires located on the first and second sides of the piezoelectric substrate layer 2 are antiparallel to the corresponding magnetization directions of the first and second fixed layers. After the first magnetic tunnel junction and the second magnetic tunnel junction are connected in parallel, they are in a high-impedance state. At this time, the logic output state is "1".

[0100] When the first ferromagnetic electrode 401 is connected to a positive voltage and the second ferromagnetic electrode 402 is grounded, the logic states A and B at the input terminals of the logic device are "10" respectively. The final magnetization direction of the ferromagnetic nanowires located on the first side of the piezoelectric substrate layer 2 is antiparallel to the magnetization direction of the corresponding first fixed layer, and the final magnetization direction of the ferromagnetic nanowires located on the second side of the piezoelectric substrate layer 2 is parallel to the magnetization direction of the corresponding second fixed layer. The first magnetic tunnel junction and the second magnetic tunnel junction are connected in parallel to form a high-impedance state. At this time, the logic output state is "1".

[0101] When the first ferromagnetic electrode 401 is grounded and the second ferromagnetic electrode 402 is connected to a positive voltage, the logic states A and B at the input terminals of the logic device are "0" and "1" respectively. The final magnetization direction of the ferromagnetic nanowires located on the first side of the piezoelectric substrate layer 2 is parallel to the magnetization direction of the corresponding first fixed layer, and the final magnetization direction of the ferromagnetic nanowires located on the second side of the piezoelectric substrate layer 2 is antiparallel to the magnetization direction of the corresponding second fixed layer. The first magnetic tunnel junction and the second magnetic tunnel junction are connected in parallel to form a high-impedance state. At this time, the logic output state is "1".

[0102] When the first ferromagnetic electrode 401 and the second ferromagnetic electrode 402 are both connected to a positive voltage, the logic states A and B at the input terminals of the logic device are "11" respectively. The final magnetization direction of the ferromagnetic nanowires located on the first side of the piezoelectric substrate layer 2 is parallel to the magnetization direction of the corresponding first fixed layer, and the final magnetization direction of the ferromagnetic nanowires located on the second side of the piezoelectric substrate layer 2 is parallel to the magnetization direction of the corresponding second fixed layer. The first magnetic tunnel junction and the second magnetic tunnel junction are connected in parallel to form a low-resistance state. At this time, the logic output state is "0".

[0103] The above logic devices implement AND and NOT logic operations.

[0104] The truth tables for the OR and AND NOT logic operations implemented by the above logic devices are shown in Table 2 below:

[0105] Table 2 Truth table corresponding to the logic devices provided in this embodiment.

[0106]

[0107] That is, by controlling the magnetization direction of the first fixed layer and the second fixed layer to be parallel or antiparallel to the final magnetization direction of the ferromagnetic nanowires located on the first and second sides of the piezoelectric substrate, different output logic states can be obtained according to the input logic state, and the OR and NAND operations of the logic device can be realized using only two logic input terminals.

[0108] The planar multiferroic heterojunction structure and the double-ended multiferroic heterojunction structure of the present invention realize the generation and movement of magnetic domain walls in magnetic nanowires by applying an external electric field between the substrate electrode layer and one of the two ferromagnetic electrodes. By applying a positive voltage or grounding to the two ferromagnetic electrodes, two different logic states can be realized as inputs. They can be used as two logic input terminals of logic devices. In the process of constructing large and complex logic networks, the input states of intermediate logic units can be controlled.

[0109] This logic device, designed based on two multiferroic heterojunction structures, is a logic device that uses electric field control to move the magnetic domain walls within the multiferroic heterojunction. By controlling the electric field of the piezoelectric substrate and aligning the magnetization direction of the fixed layer with or against the final magnetization direction of the ferromagnetic nanowire, different output logic states can be obtained by reading the state of the magnetic tunnel junction based on the input logic state. Using only two logic input terminals, it implements several of the most basic and essential logic functions of Boolean logic, improving the integration density of the logic device. Furthermore, during large-scale integration, it exhibits low power consumption due to the absence of current-driven operation, which is of great significance for the research and development of magnetic storage, magnetic logic, and in-memory computing. More importantly, the logic device designed in this invention has reconfigurable logic functions. By controlling the enable terminal (the magnetization direction of the fixed layer), the logic function can be switched. This innovative design transfers the complexity of the fabrication process to the circuit design, greatly improving the device's integrability.

[0110] Those skilled in the art will readily understand that the above description is merely 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 within the scope of protection of the present invention.

Claims

1. A multiferroic heterostructure, characterized in that, include: Substrate electrode layer, piezoelectric substrate layer (2), ferromagnetic thin film layer, first ferromagnetic electrode (401) and second ferromagnetic electrode (402); The substrate electrode layer is disposed on the piezoelectric substrate layer (2); The ferromagnetic thin film layer includes a first ferromagnetic coupling region (301), a second ferromagnetic coupling region (304), and a ferromagnetic nanowire (302) connecting the two ferromagnetic coupling regions; the first ferromagnetic coupling region (301) and the second ferromagnetic coupling region (304) are disposed on other surfaces of the piezoelectric substrate layer (2), and the other surfaces correspond to the surfaces of the substrate electrode layer disposed on the piezoelectric substrate layer (2); The first ferromagnetic electrode (401) covers the first ferromagnetic coupling region (301), and the second ferromagnetic electrode (402) covers the second ferromagnetic coupling region (304); The ferromagnetic nanowire (302) serves as the active region. A voltage is applied between the substrate electrode layer and the ferromagnetic electrode to generate an electric field at both ends of the piezoelectric substrate layer. Under the coupling effect between the piezoelectric substrate layer and the ferromagnetic coupling region, the generation and movement of magnetic domains in the ferromagnetic nanowire (302) are controlled. The ferromagnetic electrode is either the first ferromagnetic electrode (401) or the second ferromagnetic electrode (402), and the ferromagnetic coupling region is either the first ferromagnetic coupling region (301) or the second ferromagnetic coupling region (304). The substrate electrode layer includes a first substrate electrode layer (101) and a second substrate electrode layer (102), the first substrate electrode layer (101) and the second substrate electrode layer (102) are respectively disposed on two adjacent surfaces of the piezoelectric substrate layer (2); the ferromagnetic thin film layer is disposed on the other two surfaces of the piezoelectric substrate layer (2) corresponding to the first substrate electrode layer (101) and the second substrate electrode layer (102), and the other two surfaces are referred to as the first side surface and the second side surface, respectively. The first ferromagnetic coupling region (301) is located on the first side of the piezoelectric substrate (2), and the second ferromagnetic coupling region (304) is located on the second side of the piezoelectric substrate (2).

2. The multiferroic heterostructure according to claim 1, characterized in that, The substrate electrode layer is disposed on one surface of the piezoelectric substrate layer (2), and the first ferromagnetic coupling region (301) and the second ferromagnetic coupling region (304) are disposed on the other surface of the piezoelectric substrate layer (2) corresponding to the substrate electrode layer.

3. The multiferroic heterostructure according to claim 1, characterized in that, The lengths of the ferromagnetic nanowires (302) located on the first and second sides of the piezoelectric substrate (2) are equal.

4. The multiferroic heterostructure according to claim 2, characterized in that, The ferromagnetic thin film layer is prepared into a dumbbell shape by photolithography. The two ends of the dumbbell shape are the first ferromagnetic coupling region (301) and the second ferromagnetic coupling region (304), and the middle region of the dumbbell shape is the ferromagnetic nanowire (302).

5. The multiferroic heterostructure according to any one of claims 1-4, characterized in that, The piezoelectric substrate is made of lead magnesium niobate-lead titanate, and the ferromagnetic thin film is made of Ni.

6. A logic device for controlling the movement of magnetic domain walls in a multiferroic heterojunction, characterized in that, include: A multiferroic heterostructure, a tunneling layer (5), and a fixing layer (6) disposed on the tunneling layer (5); wherein the multiferroic heterostructure is the multiferroic heterostructure as described in claim 2 or 4; The tunneling layer (5) is disposed above the ferromagnetic nanowire (302). The ferromagnetic nanowire (302), the tunneling layer (5) and the fixing layer (6) form a magnetic tunnel junction structure from bottom to top, serving as the output terminal of the logic device. The first ferromagnetic electrode (401) and the second ferromagnetic electrode (402) serve as the two input terminals of the logic device.

7. The logic device according to claim 6, characterized in that, The magnetization direction of the fixed layer is controlled to be along the +x axis, so that the logic device can perform XOR logic operation; The magnetization direction of the fixed layer is controlled to be along the -x axis, so that the logic device can perform XOR logic operation; Here, the direction parallel or antiparallel to the ferromagnetic nanowire is defined as the +x axis direction, and applying a positive voltage to the first or second ferromagnetic electrode is defined as logic input "1", while grounding the first or second ferromagnetic electrode is defined as logic input "0".

8. A logic device for controlling the movement of magnetic domain walls in a multiferroic heterojunction, characterized in that, It includes a multiferroic heterostructure, a first tunneling layer (501), a second tunneling layer (502), a first fixing layer (601), and a second fixing layer (602); wherein the multiferroic heterostructure is the multiferroic heterostructure structure as described in claim 1 or 3; The first tunneling layer (501) is disposed above the ferromagnetic nanowire (302) located on the first side of the piezoelectric substrate (2), and the first fixing layer (601) is disposed on the first tunneling layer (501). The ferromagnetic nanowire (302), the first tunneling layer (501) and the first fixing layer (601) located on the first side of the piezoelectric substrate (2) form a first magnetic tunnel junction structure from bottom to top. The second tunneling layer (502) is disposed above the ferromagnetic nanowire (302) located on the second side of the piezoelectric substrate (2), and the second fixing layer (602) is disposed on the second tunneling layer (502). The ferromagnetic nanowire (302), the second tunneling layer (502) and the second fixing layer (602) located on the second side of the piezoelectric substrate (2) form a second magnetic tunnel junction structure from bottom to top. The first ferromagnetic electrode (401) and the second ferromagnetic electrode (402) serve as the two logic input terminals of the logic device, and the first magnetic tunnel junction structure and the second magnetic tunnel junction structure are connected in parallel to serve as the output terminal of the logic device.

9. The logic device according to claim 8, characterized in that, The magnetization direction of the first fixed layer is controlled to be along the +z axis and the magnetization direction of the second fixed layer is controlled to be along the -y axis, so that the logic device can perform OR logic operation; The magnetization direction of the first fixed layer is controlled to be along the -z axis and the magnetization direction of the second fixed layer is controlled to be along the +y axis, so that the logic device can perform AND and NOT logic operations; Here, the direction parallel or antiparallel to the ferromagnetic nanowires located on the first side of the piezoelectric substrate is defined as the +z axis direction, and the direction parallel or antiparallel to the ferromagnetic nanowires located on the second side of the piezoelectric substrate is defined as the +y axis direction; applying a positive voltage to the first or second ferromagnetic electrode is defined as logic input "1", and grounding the first or second ferromagnetic electrode is defined as logic input "0".

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