JP2010212342A - Magnetic memory using voltage induced magnetization reversal, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic memory capable of eliminating the need of a high current density for magnetization reversal, suppressing the decline of the thermal stability of magnetization and achieving a high recording density. <P>SOLUTION: In the magnetic memory, the movable layer of a magnetic element is the 2-layer structure of a ferromagnetic layer and an oxide antiferromagnetic layer having an electromagnetic effect, and voltage induced magnetization reversal is used as an information input system. The method of manufacturing the magnetic memory using the voltage induced magnetization reversal as the information input system includes a Cr layer formation step of epitaxially growing and forming a threefold symmetry Cr(110) layer on an Au(111) layer and a Cr layer formation step of oxidizing the formed Cr(110) layer and forming a threefold symmetry Cr<SB>2</SB>O<SB>3</SB>(0001) layer as a method of forming the oxide antiferromagnetic layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic memory using voltage-induced magnetization reversal and a method for manufacturing the same, and more particularly to a voltage induction of a two-layer structure in which a movable layer of a magnetic element is a ferromagnetic layer and an oxide antiferromagnetic layer having an electromagnetic effect. The present invention relates to a magnetic memory using magnetization reversal and a manufacturing method thereof.

  A magnetic memory has a magnetic element having an insulator sandwiched between upper and lower ferromagnets, and the magnetization directions of the upper and lower ferromagnets are parallel (same) and antiparallel (reverse). This utilizes the fact that the tunnel current (tunnel resistance) of the insulator is different, and is excellent in non-volatility, rewrite resistance, high-speed response, and the like. For this reason, it is widely used in various fields.

  For writing (inputting information) to a conventional magnetic memory, for example, a bit line in the horizontal direction upward and a word line for writing in the vertical direction (hereinafter abbreviated as “word line”) are all used. Many magnetic elements are arranged at intervals, and a magnetic element is arranged at the intersection of the word line and the bit line when viewed from above, and electricity is passed through the word line and the bit line. This is done by making the magnetization direction of the body parallel or anti-parallel to the upper ferromagnetic body.

In the case of such an MRAM (Magnetic Random Access Memory) using a conventional magnetic memory, consumer products are limited to about 4 Mb and a recording density of about 1 kbit / inch ² . However, the demands of users for increasing the storage capacity and miniaturization of magnetic memory in recent years have become increasingly severe, and various research and development aimed at realizing a magnetic memory having a recording density of 1 Tbit / inch ² or more. Has been made.

In order to realize such a recording density of 1 Tbit / inch ² or more, the element size needs to be about 10 nm × 10 nm, and accordingly, the bit line and the word line also need to be thinned. However, in the conventional magnetic memory, when the element size is reduced, it is necessary to increase the induction magnetic field necessary for reversing the magnetization direction (magnetization reversal), and a large current density is required. For example, in the element having a size of about 10 nm × 10 nm, a current density of 1.6 × 10 ⁸ A / cm ² is required to generate a write magnetic field of 100 Oe.

However, since such a large current density exceeds the allowable limit of the bit line and the word line at the time of writing, the above-described 100 Oe write magnetic field cannot be generated, and at present, it is 1 Tbit / inch ² or more. It was difficult to obtain a high recording density.

  Thus, it has been proposed to use techniques such as spin injection magnetization reversal (Patent Document 1, Non-Patent Document 1), microwave induced magnetization reversal (Non-Patent Document 2), etc., instead of the conventional magnetization reversal by an induced magnetic field. .

JP 2004-186274 A

J. et al. Hayaka et al. IEEE Transactions on Magnetics 44, 1962 (2008) S. Okamoto et al. Applied Physics Letters 93, 10256 (2008)

However, even in the spin injection magnetization reversal, a large recording current of 10 ⁶ A / cm ² or more must be passed through the word line and the bit line in order to reverse the magnetization by the spin polarization current. Difficult to get.

  Also, in microwave induced magnetization reversal, in order to generate an alternating magnetic field by microwaves, an induced current similar to that in the prior art is required, so that it is difficult to obtain a high recording density.

  It has also been pointed out that even if a magnetic memory with such a high recording density can be manufactured, the thermal stability of magnetization decreases due to the reduction in the size of the magnetic element accompanying the increase in recording density.

  For this reason, it has been desired to develop a magnetic memory that does not require a high current density for magnetization reversal and suppresses a decrease in the thermal stability of the magnetization to enable a high recording density.

  As a result of intensive studies aimed at solving the above problems, the present inventor has found that the movable layer of the magnetic element has a two-layer structure of a ferromagnetic layer and an oxide antiferromagnetic layer having an electromagnetic effect. There is a magnetic memory that uses voltage-induced magnetization reversal of an oxide antiferromagnetic layer for input, and has excellent thermal stability in the direction of magnetization despite being a nanomagnetic material, and a method for manufacturing the same Invented. The invention of each claim will be described below.

The invention described in claim 1
The movable layer of the magnetic element has a two-layer structure of a ferromagnetic layer and an oxide antiferromagnetic layer having an electromagnetic effect,
A magnetic memory using voltage-induced magnetization reversal, characterized in that voltage-induced magnetization reversal is used as an information input method.

  In the invention of this claim, unlike the conventional input of information using current, the movable layer has a two-layer structure of a ferromagnetic layer and an oxide antiferromagnetic layer having an electromagnetic effect. Using an element, a voltage is applied to cause spin reversal in the oxide antiferromagnetic layer (voltage-induced magnetization reversal), and magnetic coupling at the interface between the oxide antiferromagnetic layer and the ferromagnetic layer ( By switching magnetic anisotropy), the magnetic field of the ferromagnetic layer is also reversed, and the magnetic field of the movable layer is reversed, that is, information is input.

As described above, according to the present invention, when inputting information, unlike the prior art, it is not necessary to flow electricity with a large current density to a bit line, a word line, etc., so that power consumption can be greatly reduced. In addition, even an element having a size of about 10 nm × 10 nm can sufficiently input information, and a magnetic memory with a high recording density of 1 Tbit / inch ² or more can be provided.

  In addition, the use of magnetic coupling at the interface between the oxide antiferromagnetic material layer and the ferromagnetic material layer can suppress a decrease in thermal stability, and even a nano-sized magnetic material can maintain recording. A magnetic memory with excellent performance can be provided. In addition, a magnetic memory excellent in high-speed response (about 10 ns) can be provided.

  Furthermore, in the present invention, the voltage required for the magnetization reversal is determined by the electric field strength (V / m), so that the necessary voltage is reduced as the element size is reduced, so that further energy saving is possible. Specifically, in the prior art, a voltage of several hundred volts was necessary, but in the present invention, a voltage of several mV is sufficient.

The great effects as described above can be exhibited sufficiently not only with a magnetic memory with a high recording density of 1 Tbit / inch ² or more, but with a recording density of 1 Gbit / inch ² or more.

  And when the magnetic memory of this invention is mounted in MRAM, in addition to each effect mentioned above, it becomes possible to aim at the spread of MRAM to a consumer market by the high durability which MRAM inherently has. Specifically, for example, an alternative to FeRAM can be expected as a memory mounted on a mobile phone. From the viewpoint of high-speed response, when mounted on an automobile or the like, it can be expected to contribute by improving collision safety. The magnetic memory of the present invention can also be suitably used for a hard disk device (HDD) or the like, and can provide a hard disk device having a small storage size and a high storage capacity.

The invention described in claim 2
The oxide antiferromagnetic layer is
The magnetic memory using voltage-induced magnetization reversal according to claim 1, wherein the magnetic memory is α-Cr ₂ O ₃ or YMnO ₃ having a corundum structure.

In the present invention, α-Cr ₂ O ₃ (corundum-structured Cr ₂ O ₃ ) or corundum-structured YMnO ₃ is used as the oxide antiferromagnetic material layer. Inversion can be caused, which is preferable.

That is, by using the corundum structure, it is possible to use the electromagnetic effect, so that electric field-induced magnetization reversal can be generated with a small electric field. Among these, α-Cr ₂ O ₃ is preferable.

The invention according to claim 3
The α-Cr ₂ O ₃ is
3. The magnetic memory using voltage induced magnetization reversal according to claim 2, wherein the magnetic memory is formed on an Au layer.

As described above, an oxide antiferromagnetic layer having a corundum structure is preferable in order to cause field-induced magnetization reversal with a small electric field. Since Cr ₂ O ₃ formed on the Au layer is easily and stably formed as Cr ₂ O ₃ (α-Cr ₂ O ₃ ) having a corundum structure, electric field-induced magnetization reversal can be performed with a small electric field. The resulting magnetic memory can be easily provided. Further, since Au is used, it is preferable because it is not only chemically stable but also has a small electric resistance when reading data.

  In principle, the Au layer is preferably a finely formed Au (111) layer by epitaxial growth. In this case, Cr atoms are located in contact with three adjacent Au atoms.

  Further, although depending on the recording density and size of the magnetic memory, in the case of a nanomagnetic element, the thickness of the Au layer is preferably about 20 nm.

The invention according to claim 4
The Au layer is
4. The magnetic memory using voltage-induced magnetization reversal according to claim 3, wherein the magnetic memory is formed on an Ag layer.

As described above, α-Cr ₂ O ₃ having a corundum structure is preferable for causing electric field-induced magnetization reversal with a small electric field, and α-Cr ₂ O ₃ can be easily and stably formed on the Au layer. Can be formed. Such an Au layer can be easily formed on the Ag layer, and as a result, Cr ₂ O ₃ (α-Cr ₂ O ₃ ) having a corundum structure can be easily and stably formed. Is possible. Further, since Ag is used, it is preferable because it is chemically stable and the electric resistance at the time of reading data becomes small.

  Although depending on the recording density and size of the magnetic memory, in the case of a nanomagnetic element, the thickness of the Ag layer is about 100 nm from the aspect of relaxing the lattice distortion of Ag and ensuring the flatness of the surface. preferable.

The invention described in claim 5
The Ag layer is
5. The magnetic memory using voltage-induced magnetization reversal according to claim 4, wherein the magnetic memory is formed on a silicon layer.

In the present invention, since the Ag layer is formed on the silicon layer, the formation of the Ag layer is facilitated, whereby the formation of the Au layer is facilitated, and further, the Cr ₂ O ₃ (corundum structure) α-Cr ₂ O ₃ ) can be easily and stably formed. Further, since silicon is used, it is preferable because it is chemically relatively stable.

  Note that, in principle, the surface of the silicon layer on which the Ag layer is formed is preferably a 7 × 7-Si (111) (marked by Wood notation) surface.

The invention described in claim 6
The ferromagnetic layer is
6. The magnetic memory using voltage-induced magnetization reversal according to claim 1, wherein the magnetic memory is a Co layer.

In the present invention, since Co having ferromagnetism is used as the ferromagnetic layer, it has a sufficient effect on the tunnel junction element even if it is thin, and it is epitaxially grown with a Cr ₂ O ₃ having a corundum structure, and further has an anti-strength. Since the magnetic coupling at the interface of the magnetic layer with Cr is good, it is easy to change the direction of its own magnetization in response to the change of the spin of Cr, and the direction of magnetization for realizing the memory function is also stable.

  The Co layer is preferably a Co (111) layer formed by epitaxial growth and having twins in principle.

The invention described in claim 7
A movable layer of a magnetic element has a two-layer structure of a ferromagnetic layer and an oxide antiferromagnetic layer having an electromagnetic effect, and a method of manufacturing a magnetic memory using voltage-induced magnetization reversal as an information input method,
As a method of forming the oxide antiferromagnetic layer,
A Cr layer forming step of epitaxially growing a three-fold symmetric Cr (110) layer on the Au (111) layer;
And a Cr ₂ O ₃ layer forming step of oxidizing the formed Cr (110) layer to form a three-fold symmetric Cr ₂ O ₃ (0001) layer. Is a method of manufacturing a magnetic memory using

In the present invention, a three-fold symmetric Cr (110) layer is formed on the Au (111) layer by epitaxial growth, and the formed Cr (110) layer is oxidized to form a three-fold symmetric Cr. _{Since the 2} O ₃ (0001) layer is formed, it is possible to reliably manufacture the nano-sized magnetic element according to claim 1 and thus a magnetic memory using voltage-induced magnetization reversal.

This is formed by epitaxially growing a three-fold symmetric Cr (110) layer on the Au (111) layer, and further oxidizing the formed Cr (110) layer to form a three-fold symmetric Cr ₂ O ₃ (0001). This is because it is possible to reliably form Cr ₂ O ₃ (0001) (α-Cr ₂ O ₃ (0001)) having a corundum structure.

  As a specific means for epitaxially growing Cr (110), a method such as physical vapor deposition of Cr using a molecular beam epitaxy method or the like at 100 ° C. in vacuum can be employed.

The invention according to claim 8 provides:
As a method of forming the Au (111) layer,
The magnetism using voltage-induced magnetization reversal according to claim 7, further comprising an Au (111) layer forming step of epitaxially growing an Au (111) layer on the Ag (111) layer. A memory manufacturing method.

  In the invention of this claim, since the Au (111) layer is formed by epitaxial growth on the Ag (111) layer, the Au (111) layer according to claim 7 is extended. In addition, it is possible to reliably and easily manufacture the nano-sized magnetic element described in 1) and a magnetic memory using voltage-induced magnetization reversal.

  As a method for forming the Au (111) layer, there is a molecular beam epitaxy method or the like, specifically, “epitaxial growth on 100 nm-thick Ag (111) / 7 × 7-Si (111)”. Kingetsu et al. , J .; Appl. Phys. 90, 5104 (2001). It is described in.

The invention according to claim 9 is:
As a method of forming the Ag (111) layer,
The voltage-induced magnetization reversal according to claim 8, further comprising an Ag (111) layer forming step of performing heat treatment after forming an Ag layer on the 7 × 7-Si (111) layer. Is a method of manufacturing a magnetic memory using

  In the present invention, since an Ag layer is formed on the 7 × 7-Si (111) layer and then heat-treated to form the Ag (111) layer, the Ag ( 111) layer, and thus, the nano-sized magnetic element according to claims 1, 3, and 4, and the magnetic memory using voltage-induced magnetization reversal can be reliably manufactured.

  As a specific film formation method for the Ag layer, a molecular beam epitaxy method or the like can be employed. As a specific heat treatment method, a treatment such as exposure to an atmosphere of 400 ° C. in a vacuum for about 30 minutes can be employed.

The invention according to claim 10 is:
As a method of forming the 7 × 7-Si (111) layer,
10. The voltage-induced magnetization reversal according to claim 9, further comprising a silicon heat treatment step in which the silicon substrate is exposed to a high temperature in a vacuum and 7 × 7-Si (111) is produced on the surface thereof. A method for manufacturing a magnetic memory.

  In the present invention, 7 × 7-Si (111) layer is formed on the surface by heat treatment of exposing the silicon substrate to a high temperature in a vacuum. Thus, it is possible to reliably manufacture the nano-sized magnetic element according to claim 1, claim 3, claim 4, and claim 5, and further, a magnetic memory using voltage-induced magnetization reversal.

  In addition, as high temperature heat processing temperature, 1100-1250 degreeC is preferable and it is especially preferable in it being about 1200 degreeC. The silicon substrate is preferably a Si (111) substrate.

The invention according to claim 11
As a method of forming the ferromagnetic layer,
8. A Co (111) layer forming step for forming a Co (111) layer by epitaxial growth on the three-fold symmetric Cr ₂ O ₃ (0001) layer. 10. A method of manufacturing a magnetic memory using voltage-induced magnetization reversal according to any one of 10.

Since the invention of this claim is formed by epitaxially growing a Co (111) layer on a three-fold symmetric Cr ₂ O ₃ (0001) layer by a molecular beam epitaxy method, etc., It becomes possible to reliably manufacture the nano-sized magnetic element according to any one of claims 4, 5, and 6 and further a magnetic memory using voltage-induced magnetization reversal. In addition, the bonding at the interface between both layers is good.

The reason why Co is changed to Co (111) is that epitaxial growth is performed with Cr ₂ O ₃ (0001) having a corundum structure.

  In the present invention, a material layer that undergoes voltage-induced magnetization reversal is formed, and this phenomenon causes input to the magnetic memory. Therefore, it has low power consumption, high durability, high-speed response, and high recording density, and recording A magnetic memory having excellent retention can be provided.

It is a figure which shows the cross-sectional structure and principle of operation | movement in the magnetic element of the 1st Embodiment of this invention. 1 is a perspective view showing an arrangement of atoms in an oxide antiferromagnetic material layer in a magnetic element according to a first embodiment of the present invention. FIG. 3 is a plan view showing an arrangement of atoms when an oxide antiferromagnetic material layer is viewed from the c-axis direction in the magnetic element according to the first embodiment of the present invention. The main process at the time of forming an oxide antiferromagnetic substance layer in the magnetic element of the 1st Embodiment of this invention, and a mode that the principal part of a magnetic element is formed with the progress of the process are shown. FIG. The surface of au (111) is a diagram showing a state in which Cr of _Cr 2 _O 3 (0001) in are arranged. It is a figure which shows the mode of 3 times symmetrical rotation. It is a diagram showing the test results of the Cr ₂ O ₃ and Ag array grid by X-ray diffractometer. It is a diagram showing the magnetization characteristics of the second embodiment of 1.0nm formed on the surface of the Cr ₂ O ₃ prepared by the method shown in the form thickness of the Co layer and the temperature dependence of the present invention. Is a graph showing the temperature dependence of the magnetization of the thickness of the Co layer of 2.3nm formed on the same _Cr 2 _{O 3} surface with FIG. It is a figure which shows the measurement result of an exchange bias when the magnetic field in 5K of the same Co layer as FIG. 9 is parallel to the direction of the spin of an antiferromagnetic material layer. The measurement result of the exchange bias when the magnetic field at 5 K of the same Co layer as in FIG. 9 is orthogonal to the spin direction of the antiferromagnetic material layer 10 is shown. It is a figure which shows the structure of the magnetic element of the 3rd Embodiment of this invention.

  Hereinafter, the present invention will be described based on embodiments. Note that the present invention is not limited to the following embodiments. Various modifications can be made to the following embodiments within the same and equivalent scope as the present invention.

(First embodiment)
The present embodiment relates to a magnetic element of a magnetic memory as an object, particularly to the principle and the structure of the main part. Hereinafter, these will be described with reference to the drawings.

  FIG. 1 is a diagram showing a cross-sectional structure of a main part of a magnetic element according to a first embodiment of the present invention and the principle of operation. FIG. 1 (1) shows a case where a voltage is applied from above to below. FIG. 1 (2) shows the case where the voltage is applied from the bottom to the top. In FIG. 1, 10 is an oxide antiferromagnetic layer, 50 is a ferromagnetic layer, 80 is an upper electrode, 81 is an upper wire, 90 is a lower electrode, and 91 is a lower wire. It is. A thin arrow in the oxide antiferromagnetic layer 10 indicates the direction of spin, and a thick arrow in the ferromagnetic layer 50 indicates the magnetization direction. The oxide antiferromagnetic material layer 10 and the ferromagnetic material layer 50 constitute a movable layer.

  In an actual magnetic element, the upper electrode 80 may also serve as a fixed layer (not shown) connected to a bit line (not shown), which will be described in a later embodiment. . Further, a nonmagnetic layer and a fixed layer are further formed above the upper electrode 80 and connected to a bit line, a read word line, etc., which are directly related to the gist of the present invention. It is not shown because it is obvious and obvious.

  As shown in FIG. 1, the spin of the oxide antiferromagnetic material layer 10 is reversed by reversing the positive and negative of the upper electrode 80 and the lower electrode 90. Along with this, the spin of the ferromagnetic layer 50 magnetically coupled to the oxide antiferromagnetic layer 10 at the interface is also reversed, and the magnetic direction of the movable layer is reversed.

Oxide antiferromagnetic layer:
The material, structure, and magnetic properties of the oxide antiferromagnetic material layer 10 will be described with reference to the drawings. The oxide antiferromagnetic material layer is made of α-Cr ₂ O ₃ (corundum structure Cr ₂ O ₃ ), and the corundum structure and atomic arrangement of the oxide antiferromagnetic material are shown in FIGS. It is like. 2 is a perspective view showing a state in which atoms are arranged in the corundum structure so as to be displaced in the vertical direction, and FIG. 3 is a plan view of the corundum structure shown in FIG. 2 viewed from the c-axis direction. 2 and 3, 10c indicated by ◯ is a chromium atom, and 10o indicated by ◎ is an oxygen atom. Of the two types of black arrows, the thick arrow is the movement of Cr ions, and the thin arrow is the direction of the Cr spin. Of the two types of white arrows, the thick and short arrows indicate the movement of O ions, and the thick and long arrows indicate the direction of the electric field. In addition, the crosses in some white circles indicate that the spin direction is upward with respect to the page.

In this α-Cr ₂ O ₃ crystal structure, a = b = 4.954 Å and c = 13.584 、, and the spin direction of Cr is parallel to the c-axis. 2 is the vertical direction of the figure, and in FIG. 3, the direction is perpendicular to the paper surface. When the electric field is reversed, the direction of Cr spin is also reversed.

(Second Embodiment)
The present embodiment relates to a manufacturing method. In particular, it relates to the formation of the oxide antiferromagnetic material layer 10 of the magnetic element shown in FIG. This will be described below with reference to the drawings.

In FIG. 4, the main steps when forming the oxide antiferromagnetic layer 10 of the magnetic element of the first embodiment and the main part of the magnetic element are formed as the process progresses. Show the state. In FIG. 4, 99 is a silicon substrate, 98 is an Ag layer formed by physical vapor deposition, 97 is an Ag (111) layer, 96 is an Au layer, and 11 is a Cr layer formed by physical vapor deposition. And 10 is α-Cr ₂ O _{3, that} is, an oxide antiferromagnetic layer, and the Ag (111) layer 97 and the Au layer 96 serve as the lower electrode 90.

The step of forming the magnetic element will be specifically described below. The following numbers correspond to the numbers in FIG.
(1) The silicon substrate 99 is heat-treated in a vacuum at 1200 ° C. for 1 minute to generate 7 × 7-Si (111) different from the inside on the surface.

(2) An Ag layer 98 having a thickness of 100 nm is formed by physical vapor deposition in a vacuum atmosphere at 0 ° C. on the silicon surface after the heat treatment.

(3) Exposure to an atmosphere of 400 ° C. for 30 minutes in a vacuum makes the surface an Ag (111) layer 97.

(4) The Au (111) layer 96 is epitaxially grown to a thickness of 20 nm by physical vapor deposition such as molecular beam epitaxy in a vacuum at 100 ° C.

(5) The Cr (110) layer 11 is epitaxially grown to a thickness of 20 nm by physical vapor deposition such as molecular beam epitaxy in a vacuum at 50 ° C.

(6) Exposure to an oxygen atmosphere at 800 ° C. and 3 × 10 ⁻⁵ Torr for 30 minutes to oxidize Cr to α-Cr ₂ O ₃ .

(7) At 2.3 ° C. on the surface of α-Cr ₂ O ₃ by molecular beam epitaxy in an atmosphere of 100 ° C., base pressure of 5 × 10 ⁻¹¹ Torr or less, and deposition of 5 × 10 ⁻¹⁰ Torr or less. A Co (111) thin film layer 50 having crystals is epitaxially grown.

  In addition, in order to actually form the magnetic elements of the fine magnetic memory by arranging them on the lattice on the substrate, other processes such as forming a resist at a necessary place or removing the resist are necessary. Similarly, in order to obtain a magnetic element, it is necessary to form an upper electrode layer, an insulator layer, an upper ferromagnetic layer and the like on the epitaxially grown Co (111) thin film layer 50. Similarly, in order to complete a magnetic memory, it is necessary to form bit lines, word lines, and the like. However, these matters are all well-known techniques. For this reason, the description about the method and process for forming them is omitted.

  In addition, in order to perform performance inspections and research and confirmation of physical properties, magnetic memories and magnetic elements having a Co thickness of 1.0 nm and the like were also produced.

Explanation of stacking in the α-Cr ₂ O ₃ layer:
Au (111) is formed by the steps (1) to (4), Cr (110) is formed by three-fold symmetry in the step (5), and Cr is further formed in the step (6). ₂ O ₃ (0001) is formed by three-fold symmetry rotation.

FIG. 5 shows a state in which Cr in Cr ₂ O ₃ (0001) is arranged on the surface of Au (111). FIG. 6 shows three times of Cr atoms in Cr (110) on the surface of Au (111). Symmetrical rotation (Nishiyama-Wassaman orientation relationship) is shown. In FIG. 5, 97a indicated by a large white circle is a gold atom, and 10c indicated by a small white circle is a Cr atom of the layer of interest in Cr ₂ O ₃ (0001). Further, in FIG. 6, small white circles 10c with 1 inside are Cr atoms of the layer of interest in Cr ₂ O ₃ (0001), and small white circles 10c with 2 inside are Au (111). Cr atoms arranged on the surface.

In FIG. 5, an equilateral triangle having a side of 5.767Å indicates a unit cell of Au (111). In addition, the rhombus indicates a unit cell of Cr ₂ O ₃ (0001), and the lattice mismatch is found to be −0.8%.

In FIG. 6, a rectangle indicated by a diagonal line in which Cr of the layer of interest occupies the apex (note that this rectangle indicates a unit cell of Cr (110)) is rotated by 120 °, and Cr ₂ O ₃ ( It can be seen that it matches the Cr atom position in (0001).

FIG. 7 shows the inspection result of the lattice arrangement of Cr ₂ O ₃ (1-104) and Ag (200) by an X-ray diffractometer. The upper figure is Cr ₂ O ₃ , the lower figure is Ag, the vertical axis is the intensity, and the horizontal axis is the diffraction angle, but it can be seen that the atoms are arranged neatly.

Co layer magnetic properties:
FIG. 8 shows a Co layer having a thickness of 2.3 nm formed on the upper surface of Cr ₂ O ₃ (0001) / Au (111) / Ag (111) / Si (111) manufactured by the above method. The magnetization characteristics of are shown. FIG. 8 shows the relationship between the magnetization characteristic (M) at room temperature (RT) and the magnetic field (H), the vertical axis is the magnetization (emu) per unit volume (1 cc), and the horizontal axis is the magnetic field. A solid line indicates a case where a magnetic field indicated by H in the drawing is parallel to the Co layer, and a broken line indicates a case where the magnetic field is vertical.

  FIG. 8 shows that a residual magnetization of about 500 emu / cc and a coercive force of about 50 Oe are observed at room temperature, and there are differences in the magnetization curves depending on the direction of the magnetic field.

  FIG. 9 shows the temperature dependence of the magnetization of the Co layer manufactured by the same method as in FIG. 9 shows the case where the magnetic field is perpendicular to the spin direction of the antiferromagnetic layer 10, the right figure shows the case where the magnetic field is parallel, the vertical axis shows the magnetization (emu), and the horizontal axis shows the temperature. (K), the solid line indicates that there is a magnetic field (FC), and the dotted line indicates that there is no magnetic field (ZFC).

From FIG. 9, regardless of the direction of the magnetic field, the temperature dependence of the magnetization of FC and ZFC is different, when the magnetic field is parallel to the Co layer, a peak is observed at 295K, and the magnetic field is perpendicular to the Co layer. It can be seen that the FC magnetization disappears at 295K or higher, and that the ZFC magnetization has a peak at 295K. From this, Cr ₂ O ₃ (0001) and Co (111) are magnetically coupled at the interface, and the direction of magnetic coupling is parallel to the direction of Cr spin in Cr ₂ O ₃ (0001). It can be seen that the direction is perpendicular to the plane.

  FIG. 10 shows the measurement result of the exchange bias when the magnetic field at 5 K of the same Co layer as in FIG. 9 is parallel to the spin direction of the antiferromagnetic material layer 10. The vertical axis in FIG. 10 is the magnetization (emu), the horizontal axis is the magnetic field (kOe), the solid line is with magnetic field (FC), and the dotted line is with no magnetic field (ZFC). An exchange bias of about 500 Oe was confirmed in a direction perpendicular to the surface of the Cr layer.

  FIG. 11 shows the measurement result of the exchange bias when the magnetic field at 5 K of the same Co layer as in FIG. 9 is orthogonal to the spin direction of the antiferromagnetic material layer 10. The vertical axis in FIG. 10 is the magnetic force / CGS electromagnetic unit (emu), the horizontal axis is the magnetic field (kOe), the solid line is with magnetic field (FC), and the dotted line is with no magnetic field (ZFC). It was confirmed that the exchange bias was almost zero in the direction parallel to the surface of the Cr layer.

(Third embodiment)
The present embodiment relates to a magnetic element. FIGS. 12A and 12B show the configuration of the magnetic element of the third embodiment. In FIG. 12, 30 is a write word line, 31 is an isolation transistor, 32 is a read word line, 40 is a bit line, 60 is a tunnel junction element, and 70 is a fixed layer ( The upper ferromagnetic layer). (1) of FIG. 12 shows a case where the upper electrode 80 is provided between the lower ferromagnetic layer 50 and the tunnel junction element 60, and (2) of FIG. 12 shows the lower ferromagnetic layer 50 and the tunnel. This is a case where the upper electrode 80 is not provided between the junction elements 60 and the upper ferromagnetic layer 70 also serves as the upper electrode 80.

  The magnetic memory of the present invention has low power consumption, high durability, high-speed response, high recording density, and excellent recording retention, so that the power consumption is severely restricted by mobile phones, vibration, heat, etc. It is expected to be used for automobiles with severe environmental aspects, especially for collision prevention devices.

10 Oxide Antiferromagnetic Layer 10c Cr Atom 10o Oxygen Atom 11 Cr (110) Layer 30 Write Word Line 31 Isolation Transistor 32 Read Word Line 40 Bit Line 50 Ferromagnetic Layer 60 Tunnel Junction Element 70 Fixed Layer ( Upper ferromagnetic layer)
80 Upper electrode 81 Upper wire 90 Lower electrode 91 Lower wire 96 Au layer 97 Ag (111) layer 98 Ag layer 99 Silicon substrate

Claims (11)

The movable layer of the magnetic element has a two-layer structure of a ferromagnetic layer and an oxide antiferromagnetic layer having an electromagnetic effect,
A magnetic memory using voltage-induced magnetization reversal, characterized in that voltage-induced magnetization reversal is used as an information input method. The oxide antiferromagnetic layer is
The magnetic memory using voltage-induced magnetization reversal according to claim 1, wherein the magnetic memory is α-Cr ₂ O ₃ or YMnO ₃ having a corundum structure. The α-Cr ₂ O ₃ is
The magnetic memory using voltage-induced magnetization reversal according to claim 2, wherein the magnetic memory is formed on an Au layer. The Au layer is
The magnetic memory using voltage-induced magnetization reversal according to claim 3, wherein the magnetic memory is formed on an Ag layer. The Ag layer is
5. The magnetic memory using voltage-induced magnetization reversal according to claim 4, wherein the magnetic memory is formed on a silicon layer. The ferromagnetic layer is
The magnetic memory using voltage-induced magnetization reversal according to any one of claims 1 to 5, wherein the magnetic memory is a Co layer. A movable layer of a magnetic element has a two-layer structure of a ferromagnetic layer and an oxide antiferromagnetic layer having an electromagnetic effect, and a method of manufacturing a magnetic memory using voltage-induced magnetization reversal as an information input method,
As a method of forming the oxide antiferromagnetic layer,
A Cr layer forming step of epitaxially growing a three-fold symmetric Cr (110) layer on the Au (111) layer;
And a Cr ₂ O ₃ layer forming step of oxidizing the formed Cr (110) layer to form a three-fold symmetric Cr ₂ O ₃ (0001) layer. Manufacturing method of magnetic memory using As a method of forming the Au (111) layer,
The magnetism using voltage-induced magnetization reversal according to claim 7, further comprising an Au (111) layer forming step of epitaxially growing an Au (111) layer on the Ag (111) layer. Memory manufacturing method. As a method of forming the Ag (111) layer,
The voltage-induced magnetization reversal according to claim 8, further comprising an Ag (111) layer forming step of performing heat treatment after forming an Ag layer on the 7 × 7-Si (111) layer. Manufacturing method of magnetic memory using As a method of forming the 7 × 7-Si (111) layer,
10. The voltage-induced magnetization reversal according to claim 9, further comprising a silicon heat treatment step in which the silicon substrate is exposed to a high temperature in a vacuum and 7 × 7-Si (111) is produced on the surface thereof. Manufacturing method of magnetic memory. As a method of forming the ferromagnetic layer,
8. A Co (111) layer forming step of forming a Co (111) layer by epitaxial growth on the three-fold symmetric Cr ₂ O ₃ (0001) layer. 11. A method for manufacturing a magnetic memory using voltage induced magnetization reversal according to any one of 10 above.

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