A polymorphic magnetic storage device and a preparation method thereof

Abstract

The present invention provides a polymorphic magnetic storage device and a preparation method thereof. The polymorphic magnetic storage device is a spin valve device based on a van der Waals heterojunction, which is mainly composed of a first magnetic layer, a non-magnetic layer, a second magnetic layer, and an insulating layer stacked to form a van der Waals heterojunction. In this van der Waals heterojunction, introducing spin accumulations with opposite polarization directions at the interfaces between the first magnetic layer and the non-magnetic layer and between the second magnetic layer and the non-magnetic layer can break the originally degenerate electron transport states, so that four resistance states can be completely presented during electrical detection. Since the four magnetic states correspond to four different resistance states, electrical detection of the four magnetic states of the two magnetic layers can be further realized, and the magnitudes and windows of the four states can be regulated by an external electric field, ultimately realizing polymorphic storage in a single storage unit.

Description

Technical Field

[0001] The present invention relates to the field of magnetic storage technology, and more specifically, to a multi-state magnetic storage device and a preparation method thereof. Background Art

[0002] As a new type of storage device, magnetic storage devices store information in the magnetic structure of the magnetic layer and have the characteristics of fast reading and writing speed, low energy consumption, and non-volatility.

[0003] The giant magnetoresistance (GMR) effect can be observed in a multilayer film structure with alternating magnetic film layers and non-magnetic film layers. The resistance value of this structural material is related to the magnetization direction of the ferromagnetic film layer. The resistance value when the two magnetic film layers have opposite magnetization directions is significantly greater than the resistance value when the magnetization directions are the same. Therefore, the resistance value can be changed by changing the magnetization direction of the two magnetic film layers.

[0004] Usually, giant magnetoresistance structure devices can only distinguish between the parallel and anti-parallel states of the two magnetic layers during electrical detection, but cannot fully distinguish the four magnetic states existing in the two magnetic film layers, thus limiting the storage density at the source.

[0005] Moreover, the giant magnetoresistance effect has high requirements on the interface quality. Traditional sputtering coating is difficult to form high-quality films at the atomic scale, and thus cannot fully present the interface effect. Summary of the invention

[0006] In view of this, in order to solve the above problems, the present invention provides a multi-state magnetic memory device and a preparation method, and the technical solution is as follows:

[0007] A multi-state magnetic memory device, comprising:

[0008] substrate;

[0009] A bottom electrode located at one side of the substrate, the bottom electrode comprising a first bottom electrode and a second bottom electrode;

[0010] a first magnetic layer located on a side of the first bottom electrode facing away from the substrate;

[0011] a non-magnetic layer located on a side of the first magnetic layer facing away from the substrate;

[0012] a second magnetic layer located on a side of the non-magnetic layer away from the substrate, the second magnetic layer extending in a first direction to cover the second bottom electrode;

[0013] The first direction is parallel to the plane where the substrate is located, and points from the first bottom electrode to the second bottom electrode;

[0014] The second magnetic layer includes a ferromagnetic layer and an antiferromagnetic layer;

[0015] The second magnetic layer includes a first portion, and the first portion is located on a side of the second bottom electrode away from the first bottom electrode;

[0016] An insulating layer located on a side of the first portion away from the substrate;

[0017] A top electrode located on a side of the insulating layer away from the substrate.

[0018] Preferably, in the above-mentioned multi-state magnetic storage device, the first magnetic layer and the second magnetic layer are made of the same material, and are van der Waals ferromagnetic metal thin films.

[0019] Preferably, in the above-mentioned multi-state magnetic storage device, the non-magnetic layer is a graphite flake.

[0020] Preferably, in the above-mentioned multi-state magnetic storage device, the thickness range of the first magnetic layer is 30 nm - 40 nm;

[0021] The thickness range of the second magnetic layer is 10 nm - 20 nm.

[0022] Preferably, in the above-mentioned multi-state magnetic storage device, the thickness range of the non-magnetic layer is 1 nm - 20 nm.

[0023] Preferably, in the above-mentioned multi-state magnetic storage device, the thickness range of the insulating layer is 5 nm - 20 nm.

[0024] Preferably, in the above-mentioned multi-state magnetic storage device, the thickness range of the bottom electrode is 5 nm - 30 nm.

[0025] Preferably, in the above-mentioned multi-state magnetic storage device, the thickness range of the top electrode is 30 nm - 50 nm.

[0026] Preferably, in the above-mentioned multi-state magnetic storage device, the multi-state magnetic storage device further includes:

[0027] A packaging layer located on a side of the multi-state magnetic storage device away from the substrate.

[0028] A method for manufacturing a multi-state magnetic storage device, the manufacturing method including:

[0029] Providing a substrate;

[0030] Forming a bottom electrode on one side of the substrate, the bottom electrode including a first bottom electrode and a second bottom electrode;

[0031] Forming a first magnetic layer on a side of the first bottom electrode away from the substrate, the first magnetic layer covering the first bottom electrode;

[0032] A non-magnetic layer is formed on a side of the first magnetic layer facing away from the substrate;

[0033] A second magnetic layer is formed on a side of the non-magnetic layer facing away from the substrate, and the second magnetic layer is pre-annealed and extends to cover the second bottom electrode;

[0034] An insulating layer is formed on a side of the second magnetic layer facing away from the substrate;

[0035] A top electrode is formed on a side of the insulating layer facing away from the substrate.

[0036] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0037] A multi-state magnetic storage device provided by the present invention is a spin valve device based on a van der Waals heterojunction. The van der Waals heterojunction is mainly composed of a first magnetic layer, a non-magnetic layer, a second magnetic layer, and an insulating layer stacked on top of each other. In this van der Waals heterojunction, introducing spin accumulations with opposite polarization directions at the interface between the first magnetic layer and the non-magnetic layer and at the interface between the second magnetic layer and the non-magnetic layer can break the original degenerate electron transport state, so that four resistance states can be completely presented during electrical detection. Since the four magnetic states correspond to four different resistance states, electrical detection of the four magnetic states of the two magnetic layers can be further realized, and the magnitudes and windows of the four states can be regulated by an external electric field, ultimately realizing multi-state storage in a single storage unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to the provided drawings.

[0039] Figure 1 It is a schematic structural diagram of a multi-state magnetic storage device provided by an embodiment of the present invention;

[0040] Figure 2 It is a partial top view structural diagram of a multi-state magnetic storage device provided by an embodiment of the present invention;

[0041] Figure 3 It is a partial top view structural diagram of a multi-state magnetic storage device provided by an embodiment of the present invention;

[0042] Figure 4 It is a partial top view structural diagram of a multi-state magnetic storage device provided by an embodiment of the present invention;

[0043] Figure 5 A partial top view structural diagram of a multi-state magnetic memory device provided by an embodiment of the present invention;

[0044] Figure 6 A schematic flow chart of a method for manufacturing a multi-state magnetic memory device provided by an embodiment of the present invention;

[0045] Figure 7 A test result of a multi-state magnetic memory device provided by an embodiment of the present invention when no gate voltage is applied to the top electrode;

[0046] Figure 8 The test result of a multi-state magnetic memory device provided by an embodiment of the present invention when a voltage of 10V is applied to the top electrode. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] Based on the contents recorded in the background technology, during the invention process of this application, the inventor discovered that introducing spin accumulation in opposite polarization directions at the two interfaces between the first magnetic layer and the non-magnetic layer and between the second magnetic layer and the non-magnetic metal layer can break the original degenerate electron transport state, thereby completely presenting four resistance states during electrical detection. The four resistance states correspond to four magnetic states. Distinguishing the four magnetic states during electrical reading is a direct method to realize polymorphic magnetic storage and thus improve storage density. It can change the current situation in which giant magnetoresistance structure devices can only distinguish between the parallel and anti-parallel states of the two magnetic layers during electrical detection.

[0049] The current existing technology uses traditional sputtering coating to achieve the layered stacking of polymorphic magnetic devices, but sputtering coating is difficult to form high-quality films at the atomic scale, so that the interface effect between the first magnetic layer and the non-magnetic layer and the interface effect between the second magnetic layer and the non-magnetic layer cannot be fully presented.

[0050] Based on the current technical defects, the present application provides a multi-state magnetic storage device and a preparation method thereof, wherein the multi-state magnetic storage device comprises:

[0051] substrate;

[0052] A bottom electrode located at one side of the substrate, the bottom electrode comprising a first bottom electrode and a second bottom electrode;

[0053] a first magnetic layer located on a side of the first bottom electrode facing away from the substrate;

[0054] A non-magnetic layer on a side of the first magnetic layer away from the substrate;

[0055] A second magnetic layer on a side of the non-magnetic layer away from the substrate, the second magnetic layer extending in a first direction to cover the second bottom electrode;

[0056] The first direction is parallel to a plane where the substrate is located and points from the first bottom electrode to the second bottom electrode;

[0057] The second magnetic layer includes a ferromagnetic layer and an antiferromagnetic layer;

[0058] The second magnetic layer includes a first portion located on a side of the second bottom electrode away from the first bottom electrode;

[0059] An insulating layer on a side of the first portion away from the substrate;

[0060] A top electrode on a side of the insulating layer away from the substrate.

[0061] A method for manufacturing a multi-state magnetic storage device, the manufacturing method comprising:

[0062] Providing a substrate;

[0063] Forming a bottom electrode on one side of the substrate, the bottom electrode including a first bottom electrode and a second bottom electrode;

[0064] Forming a first magnetic layer on a side of the first bottom electrode away from the substrate, the first magnetic layer covering the first bottom electrode;

[0065] Forming a non-magnetic layer on a side of the first magnetic layer away from the substrate;

[0066] Forming a second magnetic layer on a side of the non-magnetic layer away from the substrate, the second magnetic layer being pre-annealed and extending to cover the second bottom electrode;

[0067] Forming an insulating layer on a side of the second magnetic layer away from the substrate;

[0068] Forming a top electrode on a side of the insulating layer away from the substrate.

[0069] A polymorphic magnetic storage device provided by the present invention is a spin valve device based on a van der Waals heterojunction, which is mainly composed of a first magnetic layer, a non-magnetic layer, a second magnetic layer, and an insulating layer stacked to form a van der Waals heterojunction. In this van der Waals heterojunction, introducing spin accumulations with opposite polarization directions at the interfaces between the first magnetic layer and the non-magnetic layer and between the second magnetic layer and the non-magnetic layer can break the originally degenerate electron transport states, so that four resistance states can be completely presented during electrical detection. Since the four magnetic states correspond to four different resistance states, electrical detection of the four magnetic states of the two magnetic layers can be further realized, and the magnitudes and windows of the four states can be regulated by an external electric field, ultimately realizing polymorphic storage in a single storage unit.

[0070] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0071] Reference Figure 1 , Figure 1 is a schematic structural diagram of a polymorphic magnetic storage device provided by an embodiment of the present invention.

[0072] The polymorphic magnetic storage device includes:

[0073] A substrate 11;

[0074] A bottom electrode 12 located on one side of the substrate 11, and the bottom electrode 12 includes a first bottom electrode 121 and a second bottom electrode 122;

[0075] A first magnetic layer 13 located on the side of the first bottom electrode 121 away from the substrate 11;

[0076] A non-magnetic layer 14 located on the side of the first magnetic layer 13 away from the substrate 11;

[0077] A second magnetic layer 15 located on the side of the non-magnetic layer 14 away from the substrate 11, and the second magnetic layer 15 extends in a first direction 18 to cover the second bottom electrode 122;

[0078] The first direction 18 is parallel to the plane where the substrate 11 is located and points from the first bottom electrode 121 to the second bottom electrode 122;

[0079] The second magnetic layer 15 includes a ferromagnetic layer and an antiferromagnetic layer;

[0080] The second magnetic layer 15 includes a first part, and the first part is located on the side of the second bottom electrode 122 away from the first bottom electrode 121;

[0081] An insulating layer 16 located on the side of the first part away from the substrate 11;

[0082] A top electrode 17 located on a side of the insulating layer 16 facing away from the substrate 11.

[0083] In this embodiment, the substrate 11 includes a silicon layer and a silicon oxide layer. In a direction perpendicular to the plane of the substrate 11, the silicon oxide layer is placed on the silicon layer in a stacked manner.

[0084] Optionally, in a direction perpendicular to the substrate 11, the thickness of the silicon layer can be about 500 nm, and the thickness of the silicon oxide layer can be about 280 nm.

[0085] It should be noted that the first bottom electrode 121 and the second bottom electrode 122 are oppositely arranged on the substrate 11 and have the same extending direction. The extending direction of the first bottom electrode 121 and the second bottom electrode 122 is perpendicular to the first direction 18 in the plane of the substrate 11.

[0086] Optionally, the first bottom electrode 121 and the second bottom electrode 122 can be a combination of a chromium thin film and a gold thin film. In a direction perpendicular to the plane of the substrate 11, the chromium thin film is on the side close to the substrate, and the gold thin film is placed on the chromium thin film in a stacked manner. The role of the chromium thin film is to act as an adhesion layer to ensure good contact between the gold thin film and the substrate 11. For the two bottom electrodes 12, in a direction perpendicular to the plane of the substrate 11, their thickness should not be too thick, as being too thick easily leads to poor contact between the first magnetic layer 13 and the bottom electrode 12. Therefore, in a direction perpendicular to the plane of the substrate 11, the thickness of the chromium thin film of the first bottom electrode 121 and the second bottom electrode 122 can be about 5 nm, the thickness of the gold thin film can be about 30 nm, and the distance between the first bottom electrode 121 and the second bottom electrode 122 can be about 50 μm.

[0087] Further, referring to Figure 2 , Figure 2 is a partial top view structural schematic diagram of a multi-state magnetic storage device provided by an embodiment of the present invention.

[0088] It should be noted that the first magnetic layer 13 covers a partial area of the first bottom electrode 121. Optionally, the first magnetic layer 13 covers the middle area of the first bottom electrode 121, such that the combination of the first bottom electrode 121 and the first magnetic layer 13 is symmetric in the direction perpendicular to the first direction 18, and this combination method improves the structural stability of the device.

[0089] Optionally, the first magnetic layer 13 can be a Fe3GeTe2 thin film. To ensure the coercivity field difference between the first magnetic layer 13 and the second magnetic layer 15, in the direction perpendicular to the plane of the substrate 11, the thickness of the first magnetic layer 13 should be significantly greater than that of the second magnetic layer 15. However, if the first magnetic layer 13 is too thick, its coercivity field will be too small, resulting in a too narrow window for the antiparallel state. On the other hand, if the second magnetic layer 15 is too thin, the environmental stability of the device will be reduced.

[0090] Therefore, in the direction perpendicular to the plane of the substrate 11, the thickness range of the first magnetic layer 13 is 30 nm - 40 nm. For example, the thickness of the first magnetic layer 13 is 33 nm or 36 nm or 38 nm, etc.

[0091] Furthermore, referring to Figure 3 , Figure 3 is a partial top view structural schematic diagram of a multi-state magnetic storage device provided by an embodiment of the present invention.

[0092] It should be noted that the projection of the non-magnetic layer 14 on the substrate 11 covers a part of the area of the first magnetic layer 13 and extends in the direction perpendicular to the first direction 18 in the plane of the substrate 11. In the extending direction, the projected area of the non-magnetic layer 14 is larger than that of the first magnetic layer 13. Its function is to block the direct coupling between the first magnetic layer 13 and the second magnetic layer 15.

[0093] Optionally, the non-magnetic layer 14 is a graphite thin film. Since the graphite flakes themselves have a large positive magnetoresistance, in the direction perpendicular to the plane of the substrate 11, if the thickness is too thick, a large positive magnetoresistance background will be introduced into the device magnetoresistance, resulting in a decrease in the magnetoresistance change rate caused by the magnetization intensity reversal of the magnetic layer. Therefore, in the direction perpendicular to the plane of the substrate 11, the thickness range of the non-magnetic layer is 0.4 nm - 20 nm. For example, the thickness of the non-magnetic layer is 7 nm or 12 nm or 17 nm, etc.

[0094] Furthermore, referring to Figure 4 , Figure 4 is a partial top view structural schematic diagram of a multi-state magnetic storage device provided by an embodiment of the present invention.

[0095] Optionally, the second magnetic layer 15 includes a ferromagnetic layer and an antiferromagnetic layer.

[0096] In this embodiment, the ferromagnetic layer is an intrinsic magnetic layer, and the antiferromagnetic layer is a natural oxide layer. In the direction perpendicular to the plane of the substrate 11, the antiferromagnetic layer is placed on the ferromagnetic layer in a superposed manner.

[0097] It should be noted that the second magnetic layer 15 is pre-annealed at 50°C for 120 minutes in an oxygen atmosphere. By oxidizing the second magnetic layer 15, a natural oxide layer with antiferromagnetism is formed on the surface of the second magnetic layer 15, thereby introducing an exchange bias effect in the second magnetic layer 15, and the exchange bias effect in the second magnetic layer 15 is regulated by an electric field.

[0098] It should be noted that the second magnetic layer 15 only covers a portion of the non-magnetic layer 14 , and in the process of extending, covers a portion of the second bottom electrode 122 , and continues to extend to the side of the second bottom electrode 122 away from the first bottom electrode 121 .

[0099] Optionally, the second magnetic layer 15 may be a Fe3GeTe2 film, and the thickness of the second magnetic layer 15 is in the range of 10nm-20nm in the direction perpendicular to the plane of the substrate 11. For example, the thickness of the second magnetic layer 15 is 13nm, 16nm, 18nm, etc.

[0100] Since annealing oxidation is required to introduce exchange bias, the thickness of the second magnetic layer 15 cannot be too thin. If it is too thin, oxidation will cause the material to denature. Therefore, we choose the range of 10nm-20nm, which can introduce a significant exchange bias effect after oxidation while ensuring its own stability.

[0101] For further reference, Figure 5 , Figure 5 A partial top view structural diagram of a multi-state magnetic memory device provided by an embodiment of the present invention.

[0102] It should be noted that the insulating layer 16 covers a local area of the first portion of the second magnetic layer 15 and extends perpendicularly to the first direction 18 in the plane of the substrate 11. The top electrode 17 covers a local area of the insulating layer 16, and the center of the top electrode 17 is located at the same position as the center of the insulating layer 16.

[0103] Optionally, the insulating layer 16 is a hexagonal boron nitride film. The function of hexagonal boron nitride is to serve as a dielectric layer. If it is too thin, it may be broken down under the action of the electric field and damage the device. In addition, it is difficult to prepare a boron nitride film with a large area if it is too thin, and the device requirements cannot be met. Since boron nitride itself has good dielectric properties, it is difficult to effectively apply voltage to the second magnetic layer 15 if it is too thick, and it is difficult to achieve a control effect. Therefore, in the direction perpendicular to the plane where the substrate 11 is located, the thickness of the insulating layer 16 ranges from 5nm to 20nm. For example, the thickness of the insulating layer 16 is 8nm, 10nm, 16nm, etc.

[0104] Optionally, the top electrode 17 is a gold film, and its thickness satisfies good conductivity. Therefore, in the direction perpendicular to the plane where the substrate 11 is located, the thickness of the top electrode 17 can be set to a range of 30nm-50nm. For example, the thickness of the top electrode 17 is 30nm, 40nm, 45nm, etc.

[0105] In this embodiment, the first magnetic layer 13, the non-magnetic layer 14, the second magnetic layer 15 and the insulating layer 16 together constitute a van der Waals heterojunction, and its materials include but are not limited to a combination of Fe3GeTe2 film and graphite film. A combination of a magnetic film and a non-magnetic film with a difference in surface work function and capable of forming a good interface can all be used as device units.

[0106] Van der Waals materials can maintain the crystal structure of the bulk phase at the nanoscale, and can maintain their own electronic structure differences at the interface when forming a van der Waals heterojunction. According to the Peltier effect and the spin Seebeck effect, when electrons pass through an interface composed of materials with different chemical potentials, a thermal effect is generated at the interface, which causes non-equilibrium spin accumulation at the interface.

[0107] In the present application, when electrons pass through the heterojunction vertically, heat is released and absorbed at the two interfaces between the first magnetic layer 13 and the non-magnetic layer 14 and the second magnetic layer 15 and the non-magnetic layer 14, forming a hot end and a cold end respectively, and then spin accumulation with opposite polarization directions is formed at the upper and lower interfaces. By introducing the interface spin correlation effect, the original degenerate resistance state is distinguished, presenting four clearly distinguished resistance states.

[0108] Optionally, in another embodiment of the present application, the first magnetic layer 13 and the second magnetic layer 15 are made of the same material, and are van der Waals ferromagnetic metal films.

[0109] It should be noted that, from the above embodiments, the first magnetic layer 13 and the second magnetic layer 15 are Fe3GeTe2 thin films, and their magnetism is related to thickness. Specifically, the thinner the thickness, the greater the coercive field. When there is a difference in thickness between the first magnetic layer 13 and the second magnetic layer 15, there is a difference in the coercive field between the two, thereby forming a combination of four magnetic states. Since the differences in crystal structure and electronic structure between the two are maintained at the interface, the four magnetic states can be accurately detected electrically.

[0110] Optionally, in another embodiment of the present application, the multi-state magnetic memory device further includes:

[0111] An encapsulation layer 19 is located on a side of the multi-state magnetic memory device away from the substrate 11 .

[0112] Optionally, the encapsulation layer 19 is a silicon dioxide thin film, and the silicon dioxide thin film is deposited on the side of the van der Waals heterojunction away from the substrate 11 by sputtering coating.

[0113] Optionally, in the direction perpendicular to the plane of the substrate 11, the thickness range of the encapsulation layer 19 is 4 nm - 8 nm. For example, the thickness of the encapsulation layer is 4 nm or 5 nm or 6 nm, etc. Since the function of silicon dioxide is to act as the encapsulation layer 19 to prevent the device from being damaged by external actions, the thickness only needs to meet the encapsulation requirements.

[0114] Optionally, based on the above embodiments of the present invention, in another embodiment of the present invention, a method for manufacturing a multi-state magnetic storage device is further provided. Refer to Figure 6 , Figure 6 which is a schematic flowchart of a method for manufacturing a multi-state magnetic storage device provided by an embodiment of the present invention.

[0115] The manufacturing method includes:

[0116] S101: As Figure 1 shown, provide a substrate 11.

[0117] In this step, the substrate 11 includes a silicon wafer and silicon dioxide attached to the silicon wafer.

[0118] S102: As Figure 1 shown, form a bottom electrode 12 on one side of the substrate 11, and the bottom electrode 12 includes a first bottom electrode 121 and a second bottom electrode 122.

[0119] In this step, the first bottom electrode 121 and the second bottom electrode 122 on the substrate are prepared by using ultraviolet lithography, coating, and stripping methods.

[0120] S103: As Figure 1 shown, form a first magnetic layer 13 on the side of the first bottom electrode 121 away from the substrate 11, and the first magnetic layer 13 covers the first bottom electrode 121.

[0121] S104: As Figure 1 shown, form a non-magnetic layer 14 on the side of the first magnetic layer 13 away from the substrate 11.

[0122] S105: As Figure 1 shown, form a second magnetic layer 15 on the side of the non-magnetic layer 14 away from the substrate 11, and the second magnetic layer 15 extends to cover the second bottom electrode 122.

[0123] S106: As Figure 1 shown, form an insulating layer 16 on the side of the second magnetic layer 15 away from the substrate 11.

[0124] In the above four steps, the first magnetic layer 13, the non-magnetic layer 14, the second magnetic layer 15, and the insulating layer 16 are all mechanically exfoliated to obtain thin films with the required thickness, and then positioned layer by layer through dry transfer under a microscope to form a van der Waals heterojunction. Among them, the second magnetic layer 15 is pre-annealed at 50 °C in an oxygen atmosphere for 120 minutes to form a ferromagnetic layer and an antiferromagnetic layer.

[0125] S107: As Figure 1 shown, a top electrode 17 is formed on the side of the insulating layer 16 facing away from the substrate 11.

[0126] In this step, the top electrode 17 is prepared by electron beam lithography through photolithography, coating, and stripping on the insulating layer.

[0127] Optionally, as Figure 1 shown, a packaging layer 19 is formed on the side of the multi-state memory device facing away from the substrate 11.

[0128] In this embodiment, the multi-state magnetic memory device prepared through the above steps can more significantly exhibit the interface effect compared with the multi-state magnetic memory device prepared by sputtering coating, and thus distinguish the originally degenerate resistance states. The quality of the interface effect in the van der Waals heterojunction is improved, and the combination of the bulk structure and the interface effect of the first magnetic layer 13 and the second magnetic layer 15 is better realized.

[0129] Furthermore, the inventor has obtained the test results of this multi-state magnetic memory device.

[0130] Optionally, the test system of the multi-state magnetic memory device based on the van der Waals heterojunction in this application includes a digital source meter and a commercial comprehensive physical test system. The resistance corresponding to different magnetic states of the device is tested through the comprehensive physical test system, and the device is regulated by applying a gate voltage using the digital source meter.

[0131] Reference Figure 7 , Figure 7 is the test result of a multi-state magnetic memory device provided by an embodiment of the present invention when no gate voltage is applied to the top electrode.

[0132] Specifically, as Figure 7 shown, due to the thickness difference between the first magnetic layer 13 and the second magnetic layer 15, there is also a difference in their coercive fields, thus forming four magnetic state combination modes. Since the crystal structure and the electronic structure difference between the two are maintained at the interface, these four magnetic states can be accurately detected electrically.

[0133] Reference Figure 8 , Figure 8Test results of a polymorphic magnetic storage device provided by an embodiment of the present invention when a voltage of 10V is applied to the top electrode.

[0134] For the polymorphic magnetic storage device in this application, the bottom electrode 12 provides electrical detection of the device, and the top electrode 17 provides gate voltage regulation for the second magnetic layer 15. A gate voltage is applied through the top electrode 17 to change the exchange bias of the second magnetic layer 15, thereby regulating the resistance magnitudes and windows of the four resistance states.

[0135] The above has introduced in detail a polymorphic magnetic storage device and a preparation method provided by the present invention. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

[0136] It should be noted that the various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0137] It also should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements inherent to the process, method, article or device, but also other identical elements inherent to these process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0138] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A polymorphic magnetic storage device, characterized in that, The multi-state magnetic memory device comprises: substrate; A bottom electrode located at one side of the substrate, the bottom electrode comprising a first bottom electrode and a second bottom electrode; a first magnetic layer located on a side of the first bottom electrode facing away from the substrate; a non-magnetic layer located on a side of the first magnetic layer facing away from the substrate; a second magnetic layer located on a side of the non-magnetic layer away from the substrate, the second magnetic layer extending in a first direction to cover the second bottom electrode; the first magnetic layer and the second magnetic layer are made of the same material and are van der Waals ferromagnetic metal films; the first direction is parallel to the plane where the substrate is located and points from the first bottom electrode to the second bottom electrode; the second magnetic layer includes a ferromagnetic layer and an antiferromagnetic layer; the second magnetic layer includes a first portion, and the first portion is located on a side of the second bottom electrode away from the first bottom electrode; an insulating layer located on a side of the first portion facing away from the substrate; A top electrode is located on a side of the insulating layer facing away from the substrate.

2. The polymorphic magnetic storage device according to claim 1, wherein The non-magnetic layer is a graphite film.

3. The polymorphic magnetic storage device according to claim 1, wherein The thickness of the first magnetic layer is in the range of 30nm-40nm; The thickness of the second magnetic layer is in the range of 10 nm to 20 nm.

4. The polymorphic magnetic storage device according to claim 1, characterized in that, The thickness of the non-magnetic layer is in the range of 1 nm to 20 nm.

5. The polymorphic magnetic storage device according to claim 1, wherein The thickness of the insulating layer is in the range of 5nm-20nm.

6. The polymorphic magnetic storage device according to claim 1, characterized in that, The thickness of the bottom electrode is in the range of 5nm-30nm.

7. The polymorphic magnetic storage device according to claim 1, wherein The thickness of the top electrode is in the range of 30nm-50nm.

8. The polymorphic magnetic storage device according to claim 1, wherein The multi-state magnetic memory device further comprises: A packaging layer is located on the multi-state magnetic memory device and is away from the substrate.

9. A method for preparing a polymorphic magnetic storage device, characterized in that, The preparation method comprises: providing a substrate; forming a bottom electrode on one side of the substrate, wherein the bottom electrode comprises a first bottom electrode and a second bottom electrode; forming a first magnetic layer on a side of the first bottom electrode facing away from the substrate, wherein the first magnetic layer covers the first bottom electrode; forming a non-magnetic layer on a side of the first magnetic layer facing away from the substrate; A second magnetic layer is formed on a side of the non-magnetic layer away from the substrate, wherein the second magnetic layer is pre-annealed and extends to cover the second bottom electrode; the first magnetic layer and the second magnetic layer are made of the same material, which is a van der Waals ferromagnetic metal film; forming an insulating layer on a side of the second magnetic layer facing away from the substrate; A top electrode is formed on a side of the insulating layer facing away from the substrate.

Images