Magnetic tunnel junction free layer and magnetic tunnel junction structure having the same

Abstract

The application provides a magnetic tunnel junction free layer and a magnetic tunnel junction structure with the same. The magnetic tunnel junction free layer comprises a first magnetic composite layer, an antiferromagnetic spacer structure and a second magnetic composite layer which are sequentially stacked along a first direction. The first magnetic composite layer and the second magnetic composite layer are in antiferromagnetic coupling under the action of the antiferromagnetic spacer structure, and the magnetization directions thereof are opposite. Since the above structure adopts a plurality of magnetic composite layers, the overall thickness of the magnetic layer is increased while the magnetization direction is controlled to be perpendicular to the film interface, thereby increasing the data retention capability of the device. In addition, in order to reduce the write current, the above structure makes the magnetization directions of different magnetic composite layers opposite, reduces the total magnetic moment of the overall structure, thereby reducing the write current and realizing high device erasing resistance. In addition, the structure can obtain a higher TMR, thereby improving the data reading speed.

Description

Technical Field

[0001] This invention relates to the field of magnetic tunnel junction technology, and more specifically, to a magnetic tunnel junction free layer and a magnetic tunnel junction structure having the same. Background Technology

[0002] Spin Transfer Torque Magnetic Random Access Memory (STT-MRAM) is a novel type of non-volatile memory whose core storage unit is a magnetic tunnel junction (MTJ) structure. A typical MTJ structure consists of a pinned layer, a barrier layer, and a free layer. The pinned layer, also called the reference layer, maintains its magnetization direction, while only the magnetization direction of the free layer is changed to be in the same or opposite direction as the pinned layer. The MTJ structure relies on quantum tunneling to allow electrons to pass through the barrier layer. The tunneling probability of polarized electrons is related to the relative magnetization directions of the pinned and free layers. When the magnetization directions of the pinned and free layers are the same, the tunneling probability of polarized electrons is high, and the MTJ structure exhibits a low-resistance state (Rp). Conversely, when the magnetization directions of the pinned and free layers are opposite, the tunneling probability of polarized electrons is low, and the MTJ structure exhibits a high-resistance state (Rap). MRAM utilizes the Rp and Rap states of the MTJ structure to represent the logic states "1" and "0," respectively, thereby achieving data storage. The tunneling magnetoresistance value is expressed as: TMR = 100% × (R) ap -R p ) / R p .

[0003] STT-MRAM utilizes the spin-transfer torque (STT) effect of current to perform write operations on MRAM. When a spin-polarized current passes through a magnetic thin film, the polarization current interacts with the local electrons of the magnetic film, exerting a torque on the local magnetic moment of the film, causing it to tend to align with the polarization direction of the spin-polarized current. This phenomenon is called the spin-transfer torque effect (STT effect). Applying a polarization current opposite to the magnetization direction to the magnetic film, when the polarization current intensity exceeds a certain threshold, causes the magnetic moment of the film itself to flip. The spin-transfer torque effect allows the magnetization direction of the free layer in an MTJ structure to be parallel or antiparallel to the magnetization direction of the pinned layer, thus enabling the "write" operation.

[0004] MRAM applications require the MTJ structure to possess both high endurance and data retention. To achieve good data retention, the free layer of the MTJ structure needs high perpendicular magnetic anisotropy. Generally, the higher the perpendicular magnetic anisotropy of the free layer, the greater the required write current. Since current needs to pass through the barrier layer during STT-MRAM writing, the barrier layer will break down after multiple writes to the MTJ structure, leading to device failure. A higher write current is detrimental to improving endurance.

[0005] Therefore, the existing MTJ structure urgently needs to solve the problem of simultaneously maintaining high data retention capacity and high write resistance. Summary of the Invention

[0006] The main objective of this invention is to provide a magnetic tunnel junction free layer and a magnetic tunnel junction structure having the same, so as to solve the problem that the magnetic tunnel junction structure in the prior art is difficult to maintain both high data retention capacity and high write resistance at the same time.

[0007] To achieve the above objectives, according to one aspect of the present invention, a magnetic tunnel junction free layer is provided, comprising a first magnetic composite layer, an antiferromagnetic spacer structure, and a second magnetic composite layer sequentially stacked along a first direction, wherein the first magnetic composite layer and the second magnetic composite layer are antiferromagnetically coupled under the action of the antiferromagnetic spacer structure, and their magnetization directions are opposite.

[0008] Furthermore, the first magnetic composite layer includes a first ferromagnetic layer, a first spacer layer, and a second ferromagnetic layer stacked sequentially along a first direction. The magnetization directions of the first ferromagnetic layer and the second ferromagnetic layer are the same, and both magnetization directions are perpendicular to the thin film interface.

[0009] Furthermore, the material of the first spacer layer includes any one or more of Ta, Mo, W, Ti, Hf, Zr, Nb, TaN, TiN, NbN, TaB, TiB, MoB, HfB, ZrB, NbN, and WB.

[0010] Furthermore, the second magnetic composite layer includes a third ferromagnetic layer, a second spacer layer, and a fourth ferromagnetic layer stacked sequentially along the first direction. The magnetization directions of the third ferromagnetic layer and the fourth ferromagnetic layer are the same, and both magnetization directions are perpendicular to the thin film interface.

[0011] Furthermore, the material of the second spacer layer includes any one or more of Ta, Mo, W, Ti, Hf, Zr, Nb, TaN, TiN, NbN, TaB, TiB, MoB, HfB, ZrB, NbN, and WB.

[0012] Furthermore, the antiferromagnetic spacer structure includes a spacer film and an antiferromagnetic coupling layer sequentially stacked along a first direction or in a direction opposite to the first direction. The spacer film is a non-magnetic spacer layer, or the spacer film includes multiple spacer sub-films stacked along the first direction, at least one of the spacer sub-films being a non-magnetic spacer sub-film.

[0013] Furthermore, the non-magnetic spacer layer or non-magnetic spacer film is an oxide, preferably made of materials including MgO or AlO. x MgAlO x TiO x TaO x GaO x and FeO x Any one or more of the following.

[0014] Furthermore, the material of the antiferromagnetic coupling layer includes any one or more of Ru, Ir, and Cr.

[0015] Furthermore, the free layer of the magnetic tunnel junction also includes a reinforcing layer located on the side of the second magnetic composite layer away from the antiferromagnetic spacer structure. Preferably, the reinforcing layer is an oxide, and more preferably, the material of the reinforcing layer includes MgO or AlO. x MgAlO x TiO x TaO x GaO x and FeO x Any one or more of the following.

[0016] According to another aspect of the present invention, a magnetic tunnel junction is provided, comprising a reference layer, a barrier layer and a free layer stacked sequentially, wherein the free layer is the aforementioned magnetic tunnel junction free layer.

[0017] The present invention provides a magnetic tunnel junction free layer comprising a reference layer, a barrier layer, and a free layer stacked sequentially. The free layer includes a first magnetic composite layer, an antiferromagnetic spacer structure, and a second magnetic composite layer stacked sequentially in a direction away from the barrier layer. The first and second magnetic composite layers are antiferromagnetically coupled and have opposite magnetization directions. Because the above structure employs multiple magnetic composite layers, while controlling the magnetization direction to be perpendicular to the thin film interface, the overall thickness of the magnetic layers is increased, thereby increasing the data retention capability of the device. Furthermore, to reduce write current, the above structure makes the magnetization directions of the different magnetic composite layers opposite, reducing the total magnetic moment of the overall structure, thereby reducing the write current and achieving high device write / erase tolerance. In addition, this structure can achieve a higher TMR, improving data read speed. Attached Figure Description

[0018] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 A cross-sectional structural diagram of a free layer of a magnetic tunnel junction provided according to an embodiment of the present invention is shown.

[0020] Figure 2 A schematic cross-sectional view of another magnetic tunnel junction free layer provided according to an embodiment of the present invention is shown.

[0021] Figure 3 A type of Figure 1 A schematic cross-sectional view of the magnetic tunnel junction in the free layer of the magnetic tunnel junction is shown; and

[0022] Figure 4 A type of Figure 2 The diagram shows a cross-sectional view of the magnetic tunnel junction in the free layer of the magnetic tunnel junction.

[0023] The above figures include the following reference numerals:

[0024] 10. Artificial antiferromagnet; 20. Structural transition layer; 30. Reference layer; 40. Barrier layer; 50. First magnetic composite layer; 510. First ferromagnetic layer; 520. First spacer layer; 530. Second ferromagnetic layer; 60. Antiferromagnetic spacer structure; 610. Spacer film; 620. Antiferromagnetic coupling layer; 70. Second magnetic composite layer; 710. Third ferromagnetic layer; 720. Second spacer layer; 730. Fourth ferromagnetic layer; 80. Reinforcing layer. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of the invention described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] As described in the background section of this application, the existing MTJ structure urgently needs to solve the problem of simultaneously maintaining high data retention capacity and high write resistance. To address the aforementioned technical problem, the applicant of this invention provides a magnetic tunnel junction free layer, characterized by comprising a first magnetic composite layer 50, an antiferromagnetic spacer structure 60, and a second magnetic composite layer 70 sequentially stacked along a first direction. Under the action of the antiferromagnetic spacer structure 60, the first magnetic composite layer 50 and the second magnetic composite layer 70 are antiferromagnetically coupled, with opposite magnetization directions.

[0029] Because the aforementioned magnetic tunnel junction free layer employs multiple magnetic composite layers, while controlling the magnetization direction to be perpendicular to the thin film interface, the overall thickness of the magnetic layer is increased, thereby enhancing the device's data retention capability. Furthermore, to reduce write current, the aforementioned antiferromagnetic spacing structure ensures that the magnetization directions of the different magnetic composite layers are opposite, reducing the overall magnetic moment of the structure and thus lowering the write current, achieving high device write / erase tolerance. In addition, this magnetic tunnel junction free layer can achieve a high TMR, improving data read speed.

[0030] In the free layer of the magnetic tunnel junction of the present invention, the first magnetic composite layer 50 may include a first ferromagnetic layer 510, a first spacer layer 520, and a second ferromagnetic layer 530 sequentially stacked along a first direction. The magnetization directions of the first ferromagnetic layer 510 and the second ferromagnetic layer 530 are the same, and both magnetization directions are perpendicular to the thin film interface. Figure 1 and Figure 2 As shown.

[0031] The first ferromagnetic layer 510 and the second ferromagnetic layer 530 are both ferromagnetic or subferromagnetic materials. Preferably, the materials of the first ferromagnetic layer 510 and the second ferromagnetic layer 530 are independently selected from any one or more of Co, Fe, Ni, CoB, FeB, NiB, CoFe, NiFe, CoNi, CoFeNi, CoFeB, NiFeB, CoNiB, CoFeNiB, FePt, FePd, CoPt, CoPd, CoFePt, CoFePd, FePtPd, CoPtPd and CoFePtPd to achieve a stronger magnetization effect.

[0032] Preferably, the material of the first spacer layer 520 includes one or more of Ta, Mo, W, Ti, Hf, Zr, Nb, TaN, TiN, NbN, TaB, TiB, MoB, HfB, ZrB, NbN, and WB. This material ensures interlayer ferromagnetic coupling between the first ferromagnetic layer 510 and the second ferromagnetic layer 530 on both sides of the first spacer layer 520. The magnetic moments of the magnetic layers can synchronously flip with an external field or applied current. Furthermore, the interfacial interaction between the first spacer layer 520 and the two magnetic layers enhances the perpendicular magnetic anisotropy of the free layer, improves the interfacial characteristics of the free layer, and thus improves the performance of the MTJ device.

[0033] In the above-described magnetic tunnel junction free layer of the present invention, the second magnetic composite layer 70 may include a third ferromagnetic layer 710, a second spacer layer 720, and a fourth ferromagnetic layer 730 sequentially stacked along a first direction. The magnetization directions of the third ferromagnetic layer 710 and the fourth ferromagnetic layer 730 are the same, and both magnetization directions are perpendicular to the thin film interface. Figure 1 and Figure 2 As shown.

[0034] The third ferromagnetic layer 710 and the fourth ferromagnetic layer 730 are both ferromagnetic or subferromagnetic materials. Preferably, the materials of the third ferromagnetic layer 710 and the fourth ferromagnetic layer 730 are independently selected from any one or more of Co, Fe, Ni, CoB, FeB, NiB, CoFe, NiFe, CoNi, CoFeNi, CoFeB, NiFeB, CoNiB, CoFeNiB, FePt, FePd, CoPt, CoPd, CoFePt, CoFePd, FePtPd, CoPtPd and CoFePtPd.

[0035] Preferably, the material of the second spacer layer 720 includes any one or more of Ta, Mo, W, Ti, Hf, Zr, Nb, TaN, TiN, NbN, TaB, TiB, MoB, HfB, ZrB, NbN, and WB. The above materials ensure interlayer ferromagnetic coupling between the third ferromagnetic layer 710 and the fourth ferromagnetic layer 730 on both sides of the second spacer layer 720. The magnetic moments of the magnetic layers can synchronously flip with an external field or applied current. Furthermore, the interfacial interaction between the second spacer layer 720 and the two magnetic layers enhances the perpendicular magnetic anisotropy of the free layer, improves the interfacial characteristics of the free layer, and thus improves the performance of the MTJ device.

[0036] In the free layer of the magnetic tunnel junction of the present invention, the antiferromagnetic spacer structure 60 enables the first magnetic composite layer 50 and the second magnetic composite layer 70 to be antiferromagnetically coupled with opposite magnetization directions. In a preferred embodiment, the antiferromagnetic spacer structure 60 includes a spacer film 610 and an antiferromagnetic coupling layer 620 sequentially stacked along a first direction. Figure 1 As shown.

[0037] In another preferred embodiment, the antiferromagnetic spacer structure 60 includes a spacer film 610 and an antiferromagnetic coupling layer 620 sequentially stacked in a direction opposite to the first direction, such as Figure 2 As shown.

[0038] The aforementioned spacer 610 may be a single-layer non-magnetic spacer or may include multiple layers of spacer sub-films stacked along the first direction, wherein at least one of the spacer sub-films is a non-magnetic spacer sub-film.

[0039] To improve the perpendicular magnetic anisotropy of the first magnetic composite layer 50, preferably, the non-magnetic spacer film or non-magnetic spacer sub-film is an oxide; more preferably, the material of the non-magnetic spacer layer or non-magnetic spacer sub-film includes MgO or AlO. x MgAlO x TiO x TaO x GaO x and FeO x Any one or more of the following.

[0040] In order to make the first magnetic composite layer 50 and the second magnetic composite layer 70 antiferromagnetically coupled and magnetization in opposite directions, the material of the antiferromagnetic coupling layer 620 may include any one or more of Ru, Ir and Cr, but is not limited to the above-mentioned preferred types. Those skilled in the art can reasonably select the type of the antiferromagnetic coupling layer 620 according to the prior art.

[0041] The aforementioned magnetic tunnel junction free layer of the present invention may further include a reinforcing layer 80 located on the side of the second magnetic composite layer 70 away from the antiferromagnetic spacer structure 60, such as... Figure 1 and Figure 2 As shown, the aforementioned reinforcing layer 80 can improve the perpendicular magnetic anisotropy of the second magnetic composite layer 70.

[0042] Preferably, the reinforcing layer 80 is an oxide; more preferably, the material of the reinforcing layer 80 includes MgO and AlO. x MgAlO x TiO x TaO x GaO x and FeO x Any one or more of the following.

[0043] According to another aspect of the present invention, a magnetic tunnel junction is also provided, comprising a reference layer 30, a barrier layer 40, and the aforementioned magnetic tunnel junction free layer, stacked sequentially, such as... Figure 3 and Figure 4 As shown.

[0044] Because the free layer in the aforementioned magnetic tunnel junction employs a multilayer magnetic composite layer, the overall thickness of the magnetic layer is increased while controlling the magnetization direction to be perpendicular to the thin film interface, thereby enhancing the device's data retention capability. Furthermore, to reduce write current, the aforementioned antiferromagnetic spacing structure ensures that the magnetization directions of the different magnetic composite layers are opposite, reducing the overall magnetic moment of the structure and thus lowering the write current, achieving high device write and erase tolerance.

[0045] In a preferred embodiment, the magnetic tunnel junction structure of the present invention further includes an artificial antiferromagnetic material 10 and a structural transition layer 20 sequentially stacked along the side of the reference layer 30 away from the barrier layer 40, such as... Figure 3 and Figure 4 As shown. The artificial antiferromagnet 10 is used to increase the flip field of the reference layer 30, so that the magnetization direction of the reference layer remains unchanged during the writing process, and only the magnetization direction of the free layer changes. In addition, the artificial antiferromagnetic structure can reduce the bias field of the free layer and avoid the phenomenon that the free layer is unstable in a certain magnetization direction. The structural transition layer 20 is used for the structural transition between the artificial antiferromagnet 10 and the reference layer 30. The artificial antiferromagnet 10 is usually (111) crystal orientation, while the reference layer 30 needs to achieve (001) crystal orientation to achieve high TMR. Therefore, an amorphous structural transition layer is added between the two so that the artificial antiferromagnet 10 and the reference layer 30 can each achieve the optimal crystal orientation.

[0046] The beneficial effects of this application will be further illustrated below with reference to embodiments and comparative examples.

[0047] The magnetic layers and spacer films in the following embodiments are all prepared by physical vapor deposition. Target materials or raw materials with specific components are selected, and the gas flow rate, deposition power, and deposition time of the deposition process are adjusted to obtain a layer structure with a corresponding material composition and thickness.

[0048] Example 1

[0049] The free layer provided in this embodiment includes a first ferromagnetic layer 510, a first spacer layer 520, a second ferromagnetic layer 530, a spacer film 610, an antiferromagnetic coupling layer 620, a third ferromagnetic layer 710, a second spacer layer 720, and a fourth ferromagnetic layer 730 deposited sequentially. The first ferromagnetic layer 510, the second ferromagnetic layer 530, the third ferromagnetic layer 710, and the fourth ferromagnetic layer 730 are all CoFeB alloys with a thickness of 1 nm; the first spacer layer 520 and the second spacer layer 720 are both W with a thickness of 0.3 nm; the spacer film 610 is a single-layer non-magnetic spacer film made of MgO with a thickness of 1 nm; and the antiferromagnetic coupling layer 620 is Ru with a thickness of 1 nm.

[0050] Example 2

[0051] The free layer provided in this embodiment includes a first ferromagnetic layer 510, a first spacer layer 520, a second ferromagnetic layer 530, an antiferromagnetic coupling layer 620, a spacer film 610, a third ferromagnetic layer 710, a second spacer layer 720, and a fourth ferromagnetic layer 730 deposited sequentially. The first ferromagnetic layer 510, the second ferromagnetic layer 530, the third ferromagnetic layer 710, and the fourth ferromagnetic layer 730 are all CoFeB alloys with a thickness of 1 nm; the first spacer layer 520 and the second spacer layer 720 are both W with a thickness of 0.3 nm; the spacer film 610 is a single-layer non-magnetic spacer film made of MgO with a thickness of 1.2 nm; and the antiferromagnetic coupling layer 620 is Ru with a thickness of 0.8 nm.

[0052] Example 3

[0053] The free layer provided in this embodiment includes a first ferromagnetic layer 510, a first spacer layer 520, a second ferromagnetic layer 530, a spacer film 610, an antiferromagnetic coupling layer 620, a third ferromagnetic layer 710, a second spacer layer 720, a fourth ferromagnetic layer 730, and a reinforcement layer 80, deposited sequentially. Specifically, the first ferromagnetic layer 510, the second ferromagnetic layer 530, the third ferromagnetic layer 710, and the fourth ferromagnetic layer 730 are all CoFeB alloys, each with a thickness of 1 nm; the first spacer layer 520 and the second spacer layer 720 are both W, with a thickness of 0.3 nm; the spacer film 610 is a single-layer non-magnetic spacer film made of MgO, with a thickness of 1.3 nm; the antiferromagnetic coupling layer 620 is Ru, with a thickness of 0.5 nm; and the reinforcement layer is MgAl2O4, with a thickness of 1.3 nm.

[0054] Example 4

[0055] The magnetic tunnel junction provided in this embodiment includes a reference layer 30, a barrier layer 40, and the free layer in Embodiment 1, which are stacked sequentially. The reference layer 30 is made of CoFeB and has a thickness of 1 nm; the barrier layer 40 is made of MgO and has a thickness of 1 nm.

[0056] Example 5

[0057] The magnetic tunnel junction provided in this embodiment includes a reference layer 30, a barrier layer 40, and a free layer as described in Embodiment 2, which are stacked sequentially. The reference layer 30 is made of CoFeB and has a thickness of 1 nm; the barrier layer 40 is made of MgO and has a thickness of 1 nm.

[0058] Example 6

[0059] The magnetic tunnel junction provided in this embodiment includes a reference layer 30, a barrier layer 40, and a free layer as described in Embodiment 3, which are stacked sequentially. The reference layer 30 is made of CoFeB and has a thickness of 1 nm; the barrier layer 40 is made of MgO and has a thickness of 1 nm.

[0060] Example 7

[0061] The magnetic tunnel junction provided in this embodiment includes an artificial antiferromagnet 10, a structural transition layer 20, a reference layer 30, a barrier layer 40, and the free layer from Embodiment 1, stacked sequentially. The artificial antiferromagnet 10 is made of (Co0.5 / Pt0.5)7 / Ru0.45 / (Co0.5 / Pt0.5)3, with a thickness in nm. The numbers outside parentheses indicate the number of times the Co / Pt structure repeats. The structural transition layer 20 is made of Ta with a thickness of 0.3 nm. The reference layer 30 is made of CoFeB with a thickness of 1 nm. The barrier layer 40 is made of MgO with a thickness of 1 nm.

[0062] Comparative Example 1

[0063] The magnetic tunnel junction provided in this embodiment includes a reference layer, a barrier layer, and a free layer stacked sequentially. The free layer includes a first magnetic layer, a non-magnetic intermediate layer, and a second magnetic layer stacked together. The first and second magnetic layers are both CoFeB alloys with a thickness of 1 nm; the non-magnetic intermediate layer is W with a thickness of 0.3 nm.

[0064] The TMR, Delta, and endurance of the MTJ devices with magnetic tunnel junctions in the embodiments and comparative examples of this application were tested respectively, and the test results are shown in the table below.

[0065] Table 1

[0066] / TMR Data retention metrics Erasable and rewritable Example 4 200％ 113 1E7 Example 5 200％ 115 2E8 Example 6 210％ 125 3E8 Example 7 205％ 113 3E7 Comparative Example 1 190％ 65 1E6

[0067] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0068] 1. Since the free layer of the above magnetic tunnel junction adopts a multilayer magnetic composite layer, while controlling the magnetization direction to be perpendicular to the thin film interface, the overall thickness of the magnetic layer is increased, thereby increasing the data retention capability of the device.

[0069] 2. To reduce the write current, the antiferromagnetic spacing structure described above makes the magnetization directions of different magnetic composite layers opposite, reducing the total magnetic moment of the overall structure, thereby reducing the write current and achieving high device write resistance.

[0070] 3. The above-mentioned magnetic tunnel junction can achieve a higher TMR, which improves the data reading speed.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., 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 free layer of a magnetic tunnel junction, characterized in that, The system comprises a first magnetic composite layer (50), an antiferromagnetic spacer structure (60), and a second magnetic composite layer (70) sequentially stacked along a first direction. Under the action of the antiferromagnetic spacer structure (60), the first magnetic composite layer (50) and the second magnetic composite layer (70) are antiferromagnetically coupled and magnetized in opposite directions. The antiferromagnetic spacer structure (60) comprises a spacer film (610) and an antiferromagnetic coupling layer (620) sequentially stacked along the first direction or in a direction opposite to the first direction. The spacer film (610) is a non-magnetic spacer layer, or the spacer film (610) comprises multiple spacer sub-films stacked along the first direction, at least one of the spacer sub-films (610) being a non-magnetic spacer sub-film. The non-magnetic spacer layer or the non-magnetic spacer sub-film is an oxide, and the material of the non-magnetic spacer layer or the non-magnetic spacer sub-film includes MgO and AlO. x MgAlO x TiO x TaO x GaO x and FeO x The material of the antiferromagnetic coupling layer (620) includes any one or more of Ru, Ir and Cr; the magnetic tunnel junction free layer further includes a reinforcement layer (80) located on the side of the second magnetic composite layer (70) away from the antiferromagnetic spacer structure (60), and the material of the reinforcement layer (80) is MgAl2O4.

2. The free layer of the magnetic tunnel junction according to claim 1, characterized in that, The first magnetic composite layer (50) includes a first ferromagnetic layer (510), a first spacer layer (520) and a second ferromagnetic layer (530) stacked sequentially along the first direction. The magnetization directions of the first ferromagnetic layer (510) and the second ferromagnetic layer (530) are the same and both magnetization directions are perpendicular to the thin film interface.

3. The free layer of the magnetic tunnel junction according to claim 2, characterized in that, The material of the first spacer layer (520) includes any one or more of Ta, Mo, W, Ti, Hf, Zr, Nb, TaN, TiN, NbN, TaB, TiB, MoB, HfB, ZrB, NbN and WB.

4. The free layer of the magnetic tunnel junction according to claim 1, characterized in that, The second magnetic composite layer (70) includes a third ferromagnetic layer (710), a second spacer layer (720) and a fourth ferromagnetic layer (730) stacked sequentially along the first direction. The magnetization directions of the third ferromagnetic layer (710) and the fourth ferromagnetic layer (730) are the same and are perpendicular to the thin film interface.

5. The free layer of the magnetic tunnel junction according to claim 4, characterized in that, The material of the second spacer layer (720) includes any one or more of Ta, Mo, W, Ti, Hf, Zr, Nb, TaN, TiN, NbN, TaB, TiB, MoB, HfB, ZrB, NbN and WB.

6. A magnetic tunnel junction, comprising a reference layer (30), a barrier layer (40), and a free layer stacked sequentially, characterized in that, The free layer is the magnetic tunnel junction free layer as described in any one of claims 1 to 5.

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