Magnetic Memory Element and Method of Manufacturing the Same

Abstract

A magnetic memory element (100) is provided with: an antiferromagnetic layer (110) that is laminated on a substrate (2) and comprises a canted antiferromagnetic body having a magnetic order with a canted magnetic moment; a heavy metal layer (120) that is laminated on the antiferromagnetic layer (110) and comprises a non-magnetic heavy metal exhibiting a spin Hall effect; and, an oxide layer (130) on the heavy metal layer (120). The roughness of the interface between the antiferromagnetic layer (110) and the heavy metal layer (120) is 1.0 nm or less. When a write current flows in the in-plane direction to the heavy metal layer (120), a spin current is generated, and, by the spin orbit torque generated by the spin current acting on the magnetic order of the antiferromagnetic layer (110), the magnetic order can be inverted.

Description

Technical Field

[0001] The present invention relates to a magnetic memory element.

Background Art

[0002] In recent years, magnetic resistance memories using ferromagnetic materials capable of storing the direction of magnetization as "0" and "1" information have attracted attention as a representative example of non-volatile memories. Recently, a magnetization reversal phenomenon using a spin current has been found as a writing method and is being generalized. In particular, the magnetization reversal phenomenon that occurs by passing an electric current through a multilayer film composed of a ferromagnetic material and a non-magnetic heavy metal (such as tungsten (W) and platinum (Pt)) is called spin-orbit torque magnetization reversal and is actively studied as a next-generation technology.

[0003] In addition, for further speeding up of magnetic resistance memories, replacement of ferromagnetic materials with antiferromagnetic materials has been studied (see, for example, Non-Patent Document 1). The reason is that the response speed of spins in antiferromagnetic materials is 2 to 3 orders of magnitude faster than that in ferromagnetic materials in the THz band (pico (10 -12 ) seconds), and since the interaction between magnetic materials is small, there is a possibility of further speeding up and high integration of magnetic devices such as magnetic resistance memories.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] While it has been demonstrated that a magnetic memory element using an antiferromagnet can write and read information electrically in the same way as a ferromagnet, the small read signal has been a problem in applications.

[0006] The present invention has been made in view of the above problems, and an object thereof is to enhance the read signal in a magnetic memory element using an antiferromagnet.

Means for Solving the Problems

[0007] The magnetic memory element according to the present invention includes an antiferromagnetic layer made of a canted antiferromagnet having a canted magnetic order of the magnetic moment, and a contact layer that contacts the antiferromagnetic layer and is made of a material different from the canted antiferromagnet. The roughness of the interface between the antiferromagnetic layer and the contact layer is 1.0 nm or less. When a spin current flows through the contact layer, the torque generated by the spin current acts on the magnetic order of the antiferromagnetic layer, and the magnetic order can be reversed.

Effects of the Invention

[0008] According to the present invention, by setting the roughness of the interface between the antiferromagnetic layer and the contact layer to 1.0 nm or less, the interface is smoothed, the spin current injected from the contact layer into the antiferromagnetic layer through the interface is increased, and the magnetic characteristics of the antiferromagnetic layer can be optimally maintained. Therefore, it is possible to enhance the read signal of the magnetic memory element.

Brief Description of the Drawings

[0009]

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Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, throughout the drawings, the same or similar components are denoted by the same reference numerals. The drawings are schematic, and the relationship between the planar dimensions and the thickness, and the ratio of the thicknesses of the respective members are different from the actual ones. Also, it goes without saying that there are portions where the dimensional relationships and ratios are different between the drawings.

[0011] In this embodiment, the multilayer film may be denoted by the materials of the respective layers constituting the multilayer film. For example, when a layer of material b and a layer of material c are sequentially laminated on a layer of material a, this multilayer film is denoted as "material a / material b / material c". Also, the thickness (nm) of each layer may be described in parentheses after the material name. For example, a layer having a thickness of ti (nm) and made of material j is denoted as "material j(ti)".

[0012] First, with reference to FIG. 1, the configuration of a conventional magnetic memory element 1 (see Non-Patent Document 1) using an antiferromagnet will be described. The magnetic memory element 1 includes a substrate 2, a metal layer 10 on the substrate 2, an antiferromagnetic layer 11 on the metal layer 10, a heavy metal layer 12 on the antiferromagnetic layer 11, and an oxide layer 13 on the heavy metal layer 12.

[0013] The substrate 2 is made of an insulator such as Si / SiO2. The metal layer 10 is made of a metal such as ruthenium (Ru). The antiferromagnetic layer 11 is made of an antiferromagnet such as Mn3Sn. The heavy metal layer 12 is made of a nonmagnetic heavy metal such as tantalum (Ta), tungsten (W), platinum (Pt). The oxide layer 13 is a cap layer for preventing oxidation, and is made of a metal oxide such as aluminum oxide (AlOx) or magnesium oxide (MgO).

[0014] Here, the thicknesses (nm) of the metal layer 10, the antiferromagnetic layer 11, the heavy metal layer 12, and the oxide layer 13 are denoted as t0, t1, t2, and t3, respectively. For example, the magnetic memory element 1 is composed of a multilayer film of Ru(t0) / Mn3Sn(t1) / W(t2) / AlOx(t3)=Ru(2) / Mn3Sn(40) / W(5) / AlOx(5).

[0015] The magnetic memory element 1 is manufactured, for example, by forming an Ru layer (metal layer 10) and an Mn3Sn layer (antiferromagnetic layer 11) on a substrate 2 at room temperature, annealing at a predetermined temperature (e.g., 450 °C) for a predetermined time (e.g., 30 minutes), and then laminating the heavy metal layer 12 and the oxide layer 13 at room temperature.

[0016] In the conventional magnetic memory element 1, the reason for providing the Ru layer between the substrate 2 and the Mn3Sn layer is that if annealing is performed after forming the Mn3Sn layer without providing the Ru layer, the Mn3Sn layer crystallizes, the interface between the Mn3Sn layer and the heavy metal layer 12 becomes rough, and it becomes difficult to drive the device.

[0017] When an in-plane writing current is passed through the heavy metal layer 12 of the magnetic memory element 1, due to the spin Hall effect, the spin-orbit torque (SOT) acts on the magnetic order of the antiferromagnetic layer 11, and thus the direction of the magnetic order can be reversed.

[0018] Next, the magnetic memory element according to this embodiment will be described. Different from the conventional magnetic memory element 1, the magnetic memory element according to this embodiment is manufactured by an improved heat treatment process without providing an Ru layer, as will be described later.

[0019] As shown in FIG. 2A, the magnetic memory element 100 according to the present embodiment includes a substrate 2, an antiferromagnetic layer 110 made of an antiferromagnet laminated on the substrate 2, a heavy metal layer 120 which is a thin film of a nonmagnetic heavy metal laminated on the antiferromagnetic layer 110, and an oxide layer 130 on the heavy metal layer 120. Alternatively, the magnetic memory element 102 shown in FIG. 2B may be employed. In the magnetic memory element 102, the heavy metal layer 120, the antiferromagnetic layer 110, and the oxide layer 130 are laminated in this order on the substrate 2.

[0020] In the present embodiment, mainly, an example in which the contact layer in contact with the antiferromagnetic layer 110 is the heavy metal layer 120 is given, but a contact layer made of other metals or metal oxides, or a chalcogenide material such as a topological insulator may be employed. As long as a contact layer is provided on at least one side of the antiferromagnetic layer 110, the present embodiment is applicable.

[0021] Next, with reference to FIG. 3, as an example of the antiferromagnet constituting the antiferromagnetic layer 110, the characteristics of Mn3Sn will be described.

[0022] Mn3Sn is an antiferromagnet having a crystal structure called a kagome lattice based on a triangle, and as shown in FIG. 3, it has a structure in which the kagome lattices are stacked in the

[0001] direction. Manganese (Mn) located at the vertices of the kagome lattice exhibits a non-collinear magnetic structure in which the magnetic moments (the directions of the localized spins) are inclined by 120 degrees with respect to each other at a temperature of 420 K or lower due to geometric frustration. The unit of six spins of three types arranged on two layers of the kagome lattice forms a spin order called a cluster magnetic octupole represented by a hexagon. This non-collinear magnetic structure can be regarded as a ferromagnetic order (the thick arrow in the center of FIG. 3) of the cluster magnetic octupole. This ferromagnetic order macroscopically breaks time-reversal symmetry.

[0023] The cluster magnetic octupoles correspond to the Weyl points, which are topological electronic structures, and the direction of the virtual magnetic field (equivalent to 100 - 1000 Tesla (T) in real space conversion) in momentum space. The response derived from the Weyl points and the virtual magnetic field can be controlled by the direction of the cluster magnetic octupoles.

[0024] The magnetic structure as shown in FIG. 3 has orthorhombic symmetry, and only one of the three magnetic moments of Mn located at the vertices of the triangle is parallel to the easy axis of magnetization. Since the other two magnetic moments are canted with respect to the easy axis of magnetization, it is considered that a weak ferromagnetic moment is induced. In this way, an antiferromagnet with canted magnetic moments and having a small magnetization is called a canted antiferromagnet.

[0025] The crystal orientation of Mn3Sn plays an important role in enhancing the readout signal of the magnetic memory element. For example, in the measurement of the anomalous Hall effect, only the crystal grains in which the magnetic order of the cluster magnetic octupoles has a component in the plane - normal direction (perpendicular to the surface of substrate 2) contribute to the Hall voltage. However, when a Ru layer (metal layer 10) is inserted as in the conventional magnetic memory element 1 (FIG. 1), the kagome planes of Mn3Sn near the Ru layer are aligned almost in the in - plane direction (parallel to the surface of substrate 2), and the contribution to the Hall voltage becomes small. Also, the flow of current through the Ru layer is also a cause of the decrease in the readout voltage. Therefore, in this embodiment, as shown in FIGS. 2A and 2B, the magnetic memory elements 100 and 102 are provided without a Ru layer so that the Mn3Sn layer has a crystal orientation that exhibits a larger Hall voltage.

[0026] Here, when the Ru layer is not provided, as described above, if annealing is performed after depositing the heavy - metal layer 120 after forming the Mn3Sn layer (antiferromagnetic layer 110), the Mn3Sn layer crystallizes and the interface between the Mn3Sn layer and the heavy - metal layer 120 becomes rough. Therefore, in this embodiment, annealing is not performed immediately after forming the Mn3Sn layer, and annealing is performed after forming the entire multilayer film.

[0027] Regarding the manufacturing method of the magnetic memory element 100 according to this embodiment, the case of forming Mn3Sn / W / AlOx on a Si / SiO2 substrate and the case of forming Mn3Sn / Ta / AlOx will be described as examples.

[0028] In the case of Mn3Sn / W / AlOx, on a Si / SiO2 substrate, a Mn3Sn layer is deposited at room temperature using a DC magnetron sputtering apparatus with a base pressure of less than 5×10 -7 Pa. Then, a W layer is deposited at room temperature by a molecular beam epitaxy (MBE) apparatus under an ultra-high vacuum with a base pressure of less than 2×10 -8 Pa. Note that the deposition of the W layer can also be performed using a DC magnetron sputtering apparatus. Next, an AlOx layer is deposited at room temperature using an RF magnetron sputtering apparatus with a base pressure of less than 5×10 -7 Pa. All layers are deposited without breaking the vacuum. After manufacturing Mn3Sn / W / AlOx, the magnetic memory element 100 is manufactured by annealing at a predetermined temperature (for example, 450°C) for a predetermined time (for example, 30 minutes).

[0029] In the case of Mn3Sn / Ta / AlOx, on a Si / SiO2 substrate, a Mn3Sn layer and a Ta layer are deposited using a DC magnetron sputtering apparatus with a base pressure of less than 5×10 -7 Pa, and an AlOx layer is deposited using an RF magnetron sputtering apparatus. All layers are deposited at room temperature without breaking the vacuum. After forming the film of Mn3Sn / Ta / AlOx, the magnetic memory element 100 is manufactured by annealing at a predetermined temperature (for example, 500°C) for a predetermined time (for example, 30 minutes).

[0030] In this way, the magnetic memory element 100 according to this embodiment is manufactured by annealing at a temperature equal to or higher than the crystallization temperature of the antiferromagnetic layer 110 after forming all layers of the multilayer film including the antiferromagnetic layer 110. The magnetic memory element 102 shown in FIG. 2B is also manufactured by the same method.

[0031] By fabricating the magnetic memory elements 100 and 102 through an improved heat treatment process, even without providing the Ru layer, the interface between the antiferromagnetic layer 110 and the contact layer in contact with the antiferromagnetic layer 110 can be smoothed, and an enhancement of the readout signal can be expected.

[0032] Hereinafter, unless otherwise specified, the magnetic memory element 100 shown in FIG. 2A will be targeted. However, the following description also applies to the magnetic memory element 102 shown in FIG. 2B.

[0033] Next, with reference to FIGS. 4A to 4C, the anomalous Hall effect, write operation, and read operation of the magnetic memory element 100 will be described.

[0034] FIG. 4A shows the configuration of the magnetic memory element 100 having a Hall bar structure. The sample of the magnetic memory element 100 is fabricated to a predetermined size (for example, 16 μm × 96 μm). Electrodes 152 and 154 made of Au / Ti are disposed at both ends in the longitudinal direction (x direction) of the sample, and electrodes 162 and 164 made of Au / Ti are disposed in the short-side direction (y direction). A write current I write or a read current I read flows, and a Hall voltage V H is detected between the electrodes 162 and 164. Note that in FIG. 4A, the substrate 2 and the oxide layer 130 are omitted.

[0035] When writing information to the magnetic memory element 100, as shown in FIG. 4B, a write current I write (pulse current) is passed in the longitudinal direction (x direction) through the heavy metal layer 120. As a result, a spin current is generated in the plane perpendicular direction (z direction) by the spin Hall effect, and the SOT acts on the magnetic order of the antiferromagnetic layer 110, thereby reversing the magnetic order. At this time, by applying a weak bias magnetic field Hx in the x direction, the magnetic order of the antiferromagnetic layer 110 is affected by the bias magnetic field Hx, and the rotation direction of the magnetic order is determined.

[0036] In this way, information (“0” or “1”) can be written to the antiferromagnetic layer 110. The write current Iwrite Depending on the direction, the magnetic order direction of the antiferromagnetic layer 110 can be controlled. For example, when a write current I in the +x direction write flows, the magnetic order reverses from the +z direction (“1”) to the -z direction (“0”), and when a write current I in the -x direction write flows, the magnetic order reverses from the -z direction (“0”) to the +z direction (“1”).

[0037] When reading the information stored in the antiferromagnetic layer 110, as shown in FIG. 4C, a read current I read (DC) is passed in the x direction. As a result, a Hall voltage V in the y direction is generated by the anomalous Hall effect H . The sign of the Hall voltage V H is determined by the z-direction component of the magnetic order of the antiferromagnetic layer 110. For example, when the magnetic order of the antiferromagnetic layer 110 is in the +z direction, it corresponds to “1”, and when it is in the -z direction, it corresponds to “0”. In this way, the information stored according to the direction of the magnetic order of the antiferromagnetic layer 110 can be read as the Hall voltage V read by passing a read current I H .

[0038] Next, with reference to FIGS. 5A to 5D and FIG. 6, the measurement results of the anomalous Hall effect of the conventional magnetic memory element 1 and the magnetic memory element 100 of this embodiment will be described. Here, the multilayer film of the magnetic memory element 1 used for the measurement is Ru(2) / Mn3Sn(40) / W(5), and the multilayer film of the magnetic memory element 100 is Mn3Sn(40) / W(5).

[0039] In FIGS. 5A and 5B, for each of the Ru / Mn3Sn / W film and the Mn3Sn / W film, the change in the Hall voltage V with respect to the perpendicular magnetic field Hz when a read current I of 0.2 mA is applied under a perpendicular magnetic field Hz read is shown. As shown in FIGS. 5A and 5B, in both samples, an obvious hysteresis of the Hall voltage V H is observed. Also, the Hall voltage V at zero magnetic field in the Mn3Sn / W film H H ​The difference (Hall voltage change) ΔV H field is about 140 μV, which is about 1.6 times larger than the Hall voltage change of the Ru / Mn3Sn / W film.

[0040] In FIGS. 5C and 5D, for the Ru / Mn3Sn / W film and the Mn3Sn / W film respectively, the write current I write at room temperature when a bias magnetic field of μ0Hx = 0.1 T is applied in the current direction (x direction) H with respect to the Hall voltage V H is shown. Also in this case, in order to measure the Hall voltage V write after applying the write current I read a read current I of 0.2 mA is applied.

[0041] From FIG. 5C, in the Ru / Mn3Sn / W film, it can be seen that a Hall voltage change ΔV of about 25 μV write occurs when the write current I H current is applied. This behavior indicates that the spin current generated in the W layer by flowing the write current I write in the magnetic memory element 1 reverses the Hall voltage V H derived from the cluster magnetic octupoles and virtual magnetic field of Mn3Sn (reversed by spin-orbit torque). Here, from FIGS. 5A and 5C, the ratio ΔV H current / ΔV H field in the Ru / Mn3Sn / W film is about 0.29.

[0042] In the Mn3Sn / W film, from FIG. 5D, a Hall voltage change ΔV of about 70 μV write occurs when the write current I H current is applied, and it can be seen that the value of the read signal is about 3 times larger than that of the Ru / Mn3Sn / W film. Also, from FIGS. 5B and 5D, the ratio ΔV H current / ΔV H fieldSince it is about 0.5, it can be seen that the ratio at which magnetic order is reversed increases (from about 29% to about 50%) compared to the Ru / Mn3Sn / W film. Thus, in the Mn3Sn / W film, it is possible to electrically control a larger read signal (Hall voltage) than in the Ru / Mn3Sn / W film.

[0043] (Hall voltage V H ) = (read current I read ) × (Hall resistance R H ), and the Hall voltage V H increases in proportion to the read current I read . In the Mn3Sn / W film, as shown in Fig. 6, by passing a read current I write of about 3 mA, which is one-tenth of the write current I read , it was found that a Hall voltage V H of 1 mV can be extracted without being affected by the temperature rise of the magnetic memory element 100.

[0044] To examine the interface state between the Mn3Sn layer and the W layer, measurement was performed by an atomic force microscope (AFM). The surface state of the Mn3Sn / W film obtained by the AFM measurement reflects the interface state between the Mn3Sn layer and the W layer. Fig. 7 shows the AFM image of the Mn3Sn(40) / W(5) film in the Hall bar structure. The root mean square (RMS) roughness of the AFM image is defined as in Equation (1).

Equation

[0045] From the above, the increase in the readout signal in the magnetic memory element 100 of the Mn3Sn / W multilayer film is mainly due to the following reasons: (i) By removing the Ru layer, the crystal grains of the Mn3Sn layer are arranged in the plane direction that increases the readout signal, and (ii) By annealing after depositing all the layers of the multilayer film, the roughness of the interface between the Mn3Sn layer and the W layer becomes 1.0 nm or less, and the interface becomes smooth.

[0046] Next, referring to FIGS. 8 to 12, the results of various measurements (X-ray diffraction, RMS roughness, anomalous Hall effect) when the heavy metal layer 120 of the magnetic memory element 100 or 102 according to this embodiment is made of Ta will be described.

[0047] <X-ray diffraction> As described above, the magnetic memory element 100 is manufactured by annealing after depositing all the layers of the multilayer film. FIG. 8 shows the X-ray diffraction patterns of the Mn3Sn(40) / Ta(5) / Al2O3 film formed on a substrate (Si / SiO2) at different annealing temperatures T A (400 °C, 500 °C, 600 °C, 650 °C, 700 °C).

[0048] From FIG. 8, when 400 °C ≤ T A ≤ 650 °C, all the peaks in the X-ray diffraction pattern are due to Mn3Sn or the substrate (Si / SiO2), and the reaction between the Mn3Sn layer and the Ta layer is negligibly small, suggesting that the Mn3Sn layer is single-phase. On the other hand, when T A = 700 °C, a peak appears near 29°, but it is found to be unrelated to the crystal orientation of Mn3Sn. No compound (Mn-Ta, Sn-Ta, or Mn-Ta-Sn) having a large peak at this angle has been found.

[0049] <RMS roughness> FIG. 9 shows the AFM images ((a) to (e)) of the Mn3Sn(40) / Ta(5) / Al2O3 film formed at different annealing temperatures T A (400 °C, 500 °C, 600 °C, 650 °C, 700 °C). From FIG. 9, when 400 °C ≤ T AWhen it is ≤650 °C (images (a) to (d)), it can be seen that the RMS roughness slightly increases from about 0.4 nm to about 0.6 nm as T A increases. On the other hand, at T A = 700 °C (image (e)), the RMS roughness rapidly increases to about 1.4 nm. This suggests that the structure of the film has been deformed by the reaction between the Mn3Sn layer and the Ta layer.

[0050] Fig. 10 shows a transmission electron microscope (TEM) image of the cross-section of the Mn3Sn(40) / Ta(5) / Al2O3 film fabricated at T A = 500 °C. In Fig. 10, the boundaries between the layers are indicated by white lines. From the TEM image, the RMS roughness of the film surface is about 0.6 nm, while the RMS roughness at the interface between the Mn3Sn layer and the Ta layer is about 0.5 nm, which is found to be almost in agreement with the results obtained from the AFM measurement (image (b)) in Fig. 9.

[0051] <Anomalous Hall effect> Fig. 11 shows the magnetic field dependence (graphs A to E) of the anomalous Hall conductivity σ A = -ρ yx / ρ H / ρ 2 (S / cm) of the Mn3Sn(40) / Ta(5) / Al2O3(3) films fabricated at different annealing temperatures T H (400 °C, 500 °C, 600 °C, 650 °C, 700 °C). Here, ρ H is the Hall resistivity of the Mn3Sn(40) / Ta(5) layer (= V A ·(t1 + t2)), and ρ is the resistivity of the Mn3Sn(40) / Ta(5) layer. All the films shown in graphs A to E exhibit a finite hysteresis at 300 K. In particular, at T yx = 500 °C (graph B), σ A at zero magnetic field (H = 0) and 300 K takes the maximum value of 18 S / cm. On the other hand, at T yx = 700 °C (graph E), it can be seen that σ

[0052] For the Mn3Sn / Ta / Al2O3 film of the magnetic memory element 100 with the hall bar structure shown in Fig. 4A, a write current I is applied in the x direction write (pulse current of 100 ms) and a bias magnetic field of μ0Hx = 0.1 T are applied, and then a read current I of 0.2 mA read (pulse current of 500 ms) is applied to measure the hall voltage V H . Also, the hall voltage V under the vertical magnetic field Hz in the Mn3Sn / Ta / Al2O3 film H field is also measured, and the change in the hall voltage V when the magnetic order of all magnetic domains in the Mn3Sn layer is reversed H is represented by ΔV H field is obtained.

[0053] In Fig. 12, for the Mn3Sn / Ta / Al2O3 film, the change in the ratio V write to the write current I H / |ΔV H field | is shown by a solid line. Also, in Fig. 12, for the Ta(5) / Mn3Sn(40) / Al2O3(3) film of the magnetic memory element 102 shown in Fig. 2B, the change in the ratio V write to the write current I H / |ΔV H field | is shown by a dotted line. This Ta / Mn3Sn / Al2O3 film was fabricated by annealing at 500 °C after depositing all layers.

[0054] The difference between the hall voltage V write when the write current I is swept from positive to negative H (I write = +0) and the hall voltage V write when the write current I is swept from negative to positive H (I write = -0) is denoted as ΔV H current . The ratio ΔV H current / |ΔV H field | indicates the ratio of the actually reversed magnetic domains (reversal ratio) to the reversibly magnetizable all magnetic domains.

[0055] As can be seen from FIG. 12, the Mn3Sn / Ta / Al2O3 film and the Ta / Mn3Sn / Al2O3 film have opposite polarities, and it can be seen that the SOTs in opposite directions act on each other. Also, it can be seen that the inversion ratios of both films reach about 40%. Note that the difference ΔV read in the Hall voltage V H when a read current I H current of 0.2 mA is applied to the Mn3Sn / Ta / Al2O3 film is about 70 μV, which is about three times larger than the Hall voltage change ΔV H current ~25 μV of the conventional magnetic memory element 1 (Ru / Mn3Sn / W film).

[0056] From the above, in order to obtain a large read signal in the Mn3Sn / Ta / Al2O3 film, it is preferable that the reaction between the Mn3Sn layer and the Ta layer is small and the roughness of the interface between the Mn3Sn layer and the Ta layer is small. Specifically, the roughness of the interface is preferably 1.0 nm or less, and more preferably 0.6 nm or less. By reducing and smoothing the roughness of the interface in this way, it is possible to increase the spin current injected into the Mn3Sn layer through the interface and enhance the read signal of the Mn3Sn layer.

[0057] The magnetic memory element according to this embodiment can function as a magnetic random access memory (MRAM) element. Hereinafter, the magnetic memory element of the MRAM will be described with reference to FIGS. 13 and 14.

[0058] FIG. 13 shows the configuration of the magnetic memory element 200 of the SOT-MRAM. The magnetic memory element 200 includes a magnetic resistance element 210, a heavy metal layer 220, a first terminal 231, a second terminal 232, a third terminal 233, and transistors Tr1 and Tr2.

[0059] The heavy metal layer 220 is made of a non-magnetic heavy metal (such as W, Ta) showing the spin Hall effect, or a chalcogenide material such as a topological insulator. The magnetoresistive element 210 includes a free layer 212 that contacts the heavy metal layer 220 and whose magnetic order can be reversed, a non-magnetic layer 214 on the free layer 212, and a reference layer 216 that contacts the non-magnetic layer 214 and whose magnetic order is fixed in the perpendicular direction.

[0060] Similar to the antiferromagnetic layer 110 in FIGS. 2A and 2B, the free layer 212 is a thin film made of a canted antiferromagnet. The non-magnetic layer 214 is made of an insulator (for example, MgO). The reference layer 216 is made of a ferromagnet (for example, CoFeB). The magnetoresistive element 210 functions as a magnetic tunnel junction (MTJ) element.

[0061] The first terminal 231, the second terminal 232, and the third terminal 233 are made of metal. The first terminal 231 is connected to the reference layer 216, the second terminal 232 is connected to one end of the heavy metal layer 220, and the third terminal 233 is connected to the other end of the heavy metal layer 220. The first terminal 231 is connected to the ground line 240. The ground line 240 is set to a ground voltage. Note that the ground line 240 may be set to a reference voltage other than the ground voltage.

[0062] The transistors Tr1 and Tr2 are, for example, N-channel metal oxide semiconductor (NMOS) transistors. The second terminal 232 is connected to the drain of the transistor Tr1, and the third terminal 233 is connected to the drain of the transistor Tr2. The gates of the transistors Tr1 and Tr2 are connected to the word line WL. The source of the transistor Tr1 is connected to the first bit line BL1, and the source of the transistor Tr2 is connected to the second bit line BL2.

[0063] Similar to the magnetic memory elements 100 and 102 in FIGS. 2A and 2B, the magnetic memory element 200 in FIG. 13 is fabricated by forming a multilayer film composed of a heavy metal layer 220, a magnetic resistance element 210, etc. over the entire layer and then annealing at a predetermined temperature. The roughness of the interface between the free layer 212 and the heavy metal layer 220 is preferably 1.0 nm or less, and more preferably 0.6 nm or less.

[0064] In the magnetic resistance element 210, "0" and "1" data are assigned according to the resistance state. For example, when the magnetic order of the reference layer 216 and the magnetic order of the free layer 212 are in the same direction (parallel state), the magnetic resistance element 210 is in a low resistance state, and when they are in opposite directions (antiparallel state), the magnetic resistance element 210 is in a high resistance state. Therefore, the former data can be determined as "0" and the latter data as "1".

[0065] When writing data to the magnetic resistance element 210, a weak bias magnetic field is applied in the direction of the write current I write The word line WL is set to a high level to turn on the transistors Tr1 and Tr2, one of the first bit line BL1 and the second bit line BL2 is set to a high level, and the other is set to a low level. As a result, a write current I write flows between the first bit line BL1 and the second bit line BL2 in the in-plane direction of the heavy metal layer 220, generating a spin current. By SOT, the magnetic order of the free layer 212 can be reversed, and data can be written. The data to be written can be changed by the direction of the write current I write .

[0066] When reading the data stored in the magnetic resistance element 210, the word line WL is set to a high level to turn on the transistors Tr1 and Tr2, one bit line (the second bit line BL2) is set to a high level, and the other bit line (the first bit line BL1) is set to an open state. As a result, a read current I read flows from the high-level second bit line BL2 to the third terminal 233, the heavy metal layer 220, the free layer 212, the non-magnetic layer 214, the reference layer 216, the first terminal 231, and the ground line 240. Due to the magnetoresistance effect, the read current Iread By measuring the magnitude of read , the resistance state of the magnetoresistive element 210, that is, the stored data can be discriminated.

[0067] As described above, by smoothing the interface between the free layer 212 and the heavy metal layer 220, the read signal of the magnetic memory element 200 can be enhanced.

[0068] FIG. 14 shows the configuration of a magnetic memory element 300 of a magnetoresistive random access memory (STT-MRAM) that reverses magnetic order using spin transfer torque (STT). The magnetic memory element 300 includes a magnetoresistive element 310, a first terminal 321, a second terminal 322, and a transistor Tr.

[0069] The magnetoresistive element 310 includes a reference layer 316 in which magnetic order is fixed in the plane perpendicular direction, a nonmagnetic layer 314 on the reference layer 316, and a free layer 312 that contacts the nonmagnetic layer 314 and whose magnetic order can be reversed.

[0070] The free layer 312 is a thin film made of a canted antiferromagnet, similar to the antiferromagnetic layer 110 of FIGS. 2A and 2B. The nonmagnetic layer 314 is made of an insulator (for example, MgO). The reference layer 316 is made of a ferromagnet (for example, CoFeB). The magnetoresistive element 310 also functions as an MTJ element.

[0071] The first terminal 321 and the second terminal 322 are made of metal. The free layer 312 is connected to the first terminal 321, and the reference layer 316 is connected to the second terminal 322. The first terminal 321 is connected to the bit line BL, and the second terminal 322 is connected to the transistor Tr.

[0072] The transistor Tr is, for example, an NMOS transistor. The second terminal 322 is connected to the drain of the transistor Tr, the source line SL is connected to the source, and the word line WL is connected to the gate.

[0073] Similar to the magnetic memory elements 100 and 102 in FIGS. 2A and 2B, the magnetic memory element 300 in FIG. 14 is fabricated by forming a multilayer film including a magnetoresistive element 310, a first terminal 321, etc. over the entire layer and then annealing at a predetermined temperature. The roughness at the interface between the free layer 312 and the nonmagnetic layer 314 and the roughness at the interface between the free layer 312 and the first terminal 321 are preferably 1.0 nm or less, more preferably 0.6 nm or less.

[0074] Similar to the magnetoresistive element 210 in FIG. 13, "0" and "1" data are assigned to the magnetoresistive element 310 according to the resistance state.

[0075] When writing data to the magnetoresistive element 310, the word line WL is set to a high level to turn on the transistor Tr, and a writing current I in the plane perpendicular direction is applied between the bit line BL and the source line SL. write By this, the magnetic order of the free layer 312 can be reversed by STT, and data can be written. The data to be written can be changed by the direction of the writing current I. write

[0076] When reading the data stored in the magnetoresistive element 310, the word line WL is set to a high level to turn on the transistor Tr, and a reading current I is applied between the bit line BL and the source line SL. By measuring the magnitude of the reading current I due to the magnetoresistive effect, the resistance state of the magnetoresistive element 310, that is, the stored data can be discriminated. read read

[0077] As described above, by smoothing the interface between the free layer 312 and the contact layer (nonmagnetic layer 314, first terminal 321), the read signal of the magnetic memory element 300 can be enhanced.

[0078] In FIGS. 13 and 14, although an example in which the magnetoresistive elements 210 and 310 are MTJ elements is shown, they can also function as giant magnetoresistance (GMR) elements. In this case, the nonmagnetic layers 214 and 314 are made of metal (conductor).

[0079] The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention.

[0080] For example, in the above-described embodiment, Mn3Sn was cited as an example of the canting antiferromagnet, but the present embodiment is applicable to canting antiferromagnets such as those having a composition formula of Mn3X (X = Sn, Ge, Ga, Rh, Pt, Ir, etc.), Mn3YN (Y = Sn, Ni, Ga), Mn5Si3, RuO2.

Explanation of Reference Numerals

[0081] 2 substrate 100, 102, 200, 300 magnetic memory element 110 antiferromagnetic layer 120 heavy metal layer 130 oxide layer 152, 154, 162, 164 electrode 210, 310 magnetoresistive element 212, 312 free layer 214, 314 non-magnetic layer 216, 316 reference layer 220 heavy metal layer

Claims

1. An antiferromagnetic layer made of a canted antiferromagnet having a canted magnetic order with a magnetic moment cancelled, and a contact layer in contact with the antiferromagnetic layer and made of a material different from the canted antiferromagnet, comprising: the roughness of the interface between the antiferromagnetic layer and the contact layer is 1.0 nm or less, When a spin current flows through the contact layer, the torque generated by the spin current acts on the magnetic order of the antiferromagnetic layer, and the magnetic order is reversible, a magnetic memory element.

2. The magnetic memory element according to claim 1, wherein the canted antiferromagnet exhibits an anomalous Hall effect.

3. The magnetic memory element according to claim 1, wherein the canted antiferromagnet has a spin order of cluster magnetic octupoles.

4. The magnetic memory element according to claim 1, wherein the antiferromagnetic layer has the magnetic order in the plane normal direction.

5. The magnetic memory element according to claim 1, wherein the roughness of the interface is 0.6 nm or less.

6. The contact layer is made of a material exhibiting a spin Hall effect, and when a write current flows in the in-plane direction, the spin current is generated, In the antiferromagnetic layer, the magnetic order is reversible by the spin-orbit torque generated by the spin current acting on the magnetic order, the magnetic memory element according to any one of claims 1 to 5.

7. When a write current flows in the plane normal direction with respect to the contact layer and the antiferromagnetic layer, the magnetic order of the antiferromagnetic layer is reversible by spin transfer torque, the magnetic memory element according to any one of claims 1 to 5.

8. A method for manufacturing a magnetic memory element, comprising an antiferromagnetic layer made of a canted antiferromagnet having a canted magnetic order with a magnetic moment cancelled, and a contact layer in contact with the antiferromagnetic layer and made of a material different from the canted antiferromagnet and for applying a torque to the magnetic order of the antiferromagnetic layer by a spin current, forming a multilayer film composed of at least the antiferromagnetic layer and the contact layer at room temperature, After forming the entire multilayer film, annealing the multilayer film at a temperature equal to or higher than the crystallization temperature of the antiferromagnetic layer to smooth the interface between the antiferromagnetic layer and the contact layer so that the roughness becomes 1.0 nm or less, a method for manufacturing a magnetic memory element.

9. Forming the multilayer film is Depositing the antiferromagnetic layer on the substrate at room temperature, depositing the contact layer on the antiferromagnetic layer at room temperature, and depositing an oxide layer made of a metal oxide on the contact layer at room temperature; The method for manufacturing a magnetic memory element according to claim 8, comprising the above.

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