KR102236586B1 - Magnetic anisotropy-controlled magnetic memory device by proton and magnetic memory device using thereof - Google Patents

Abstract

A magnetic memory device according to an embodiment of the present invention includes: a lower electrode; A magnetic layer formed on the lower electrode; An oxide layer formed on the magnetic layer and having an open lattice structure; And an upper electrode formed on the oxide layer, wherein the upper electrode decomposes moisture around the upper electrode by a voltage applied between the upper electrode and the lower electrode to generate hydrogen ions, and the generated hydrogen The magnetic anisotropy of the magnetic layer is controlled by ions.

Description

A magnetic memory device in which magnetic anisotropy is controlled by hydrogen ions, and a magnetic memory device using the same.

The present invention relates to a magnetic memory structure and a magnetic memory device using the same, and more particularly, to a characteristic in which hydrogen ions move due to voltage application.

Recently, due to the development of IoT, artificial intelligence, and big data technologies, development of a next-generation nonvolatile memory device capable of high integration and high efficiency at low process cost is required to efficiently process and store vast amounts of data. Among the next-generation memories, magnetic memory is attracting great attention as a technology capable of replacing the existing silicon-based memory due to its characteristic non-volatile, fast operation speed, and excellent durability. Such a magnetic memory stores information according to the direction of magnetization in the magnetic tunnel junction, and in this case, it is necessary to develop a technology for lowering the energy of reversing the magnetization direction.

A method of changing the orbital structure by applying a voltage in the magnetic tunnel junction (MTJ) structure has been proposed, but it does not show satisfactory operating time (speed) and stability.

Korean Patent Publication No. 10-0232667

It is intended to provide a magnetic memory device and a magnetic memory device having improved operating speed and stability and low operating energy by controlling magnetic anisotropy by a new method from the prior art.

A magnetic memory device according to an embodiment of the present invention includes: a lower electrode; A magnetic layer formed on the lower electrode; An oxide layer formed on the magnetic layer and having an open lattice structure; And an upper electrode formed on the oxide layer, wherein the upper electrode decomposes moisture around the upper electrode by a voltage applied between the upper electrode and the lower electrode to generate hydrogen ions, and the generated hydrogen The magnetic anisotropy of the magnetic layer is controlled by ions.

The oxide layer may be a rare earth oxide.

The oxide layer may be formed of any one of Yttria-Stabilized Zirconia (YSZ), Barium Cerium Yttrium Zirconate (BZCY), and Gadolinium-doped Ceria (GDC).

The magnetic memory device may further include an antioxidant layer formed between the magnetic layer and the oxide layer to prevent oxidation of the magnetic layer.

The antioxidant layer may be made of Pd.

The upper electrode may be formed of any one or at least two compounds of Cu, Pt, and Ir.

A magnetic memory device according to an embodiment of the present invention has a cross shape, a first terminal formed at four ends of the cross shape, a second terminal formed at a position facing the first terminal, a third terminal, and the A lower electrode having a fourth terminal formed at a position facing the third terminal; A magnetic layer formed on the cross-shaped cross portion of the lower electrode; An oxide layer formed on the magnetic layer and having an open lattice structure; And an upper electrode formed on the oxide layer, wherein moisture around the upper electrode is decomposed by a gate voltage applied between the upper electrode and the first terminal of the lower electrode to generate hydrogen ions, and the generated hydrogen The magnetic anisotropy of the magnetic layer is changed by ions, and a current is generated by a switching voltage applied between the first and second terminals of the lower electrode, thereby inducing a spin orbital torque for switching the magnetization of the magnetic layer. do.

A method of driving a magnetic memory device according to an embodiment of the present invention,

A cross-shaped, formed at four ends of the cross-shaped, a first terminal, a second terminal formed at a position facing the first terminal, a third terminal, and a fourth formed at a position facing the third terminal A lower electrode on which a terminal is formed; A magnetic layer formed on the cross-shaped cross portion of the lower electrode; An oxide layer formed on the magnetic layer and having an open lattice structure; And an upper electrode formed on the oxide layer,

Applying a gate voltage between the upper electrode and the first terminal of the lower electrode, whereby moisture around the upper electrode is decomposed to generate hydrogen ions, and magnetic anisotropy of the magnetic layer is changed by the generated hydrogen ions; Applying a switching voltage between the first terminal and the second terminal of the lower electrode to generate a current in the lower electrode, thereby inducing a spin current by a spin trajectory torque for switching the magnetization of the magnetic layer; And maintaining the switched magnetization state by turning off the gate voltage and the switching voltage.

According to an embodiment of the present invention, by controlling the movement of hydrogen ions by voltage to control magnetic anisotropy, a magnetic memory device having improved durability and operation speed and low operating energy and a magnetic memory device using the same can be provided.

1 is a diagram illustrating a magnetic memory device according to an embodiment of the present invention.
2 is a view for explaining the operation of the upper electrode of FIG. 1.
3 is a diagram illustrating an example of the oxide layer of FIG. 1.
4 is a diagram illustrating a magnetic memory device according to an embodiment of the present invention.
5 is a diagram illustrating an operation of a magnetic memory device according to an embodiment of the present invention.
6 and 7 show experimental results of a magnetic memory device according to an embodiment of the present invention.
8 is a diagram illustrating a magnetic memory device according to an embodiment of the present invention.

Terms or words used in this specification and claims are limited to their usual or dictionary meanings and should not be interpreted, and that the inventor can appropriately define the concept of terms in order to describe his own invention in the best way. Based on the principle, it should be interpreted as a meaning and concept consistent with the technical idea of the present invention.

Throughout the specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless specifically stated to the contrary.

In the specification and claims, the use of a singular word when used with the term “comprising” may mean “one”, or “one or more”, “at least one”, and “one or more than one”. May be.

The use of the term "or" in the claims indicates that although the present disclosure supports only selectables and definitions representing "and/or", selectables are mutually exclusive or are only expressly indicated to represent selectables " And/or is used to mean ".

Features and advantages of the present invention will become apparent from the following detailed description. However, since various changes and modifications within the spirit and scope of the present invention will become apparent to those skilled in the art from this detailed description, the detailed description and specific examples represent specific embodiments of the present invention, but only It should be understood that it is given as an example. Various exemplary embodiments of the invention are discussed in detail below with respect to the accompanying drawings, in which exemplary embodiments of the invention are shown. While specific implementations are discussed, this is done for illustrative purposes only. Those skilled in the art will recognize that other components and configurations may be used without departing from the spirit and scope of the present invention. The same numbers represent the same elements throughout.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating a magnetic memory device 1 according to an embodiment of the present invention.

Referring to FIG. 1, the magnetic memory device 1 includes a lower electrode 110, a magnetic material layer 120, an oxide layer 130, and an upper electrode layer 140 that are sequentially stacked. The upper electrode 140 decomposes moisture around the upper electrode 140 by a voltage applied between the upper electrode 140 and the lower electrode 110 to generate hydrogen ions, and the magnetic material layer ( 120) magnetic anisotropy is controlled. Specifically, the generated hydrogen ions move to the magnetic material layer 120 by the applied voltage and influence the spin orbital coupling of the magnetic material layer 120 to control the magnetic anisotropy of the magnetic material layer 120.

FIG. 2 is a diagram for explaining the operation of the upper electrode 140 of FIG. 1.

Referring to FIG. 2, when a voltage is applied between the upper electrode 140 and the lower electrode 110, the upper electrode 140 _{decomposes the surrounding moisture (H 2} O) to decompose hydrogen ions (H ⁺ ) and oxygen ( O ₂ ) is generated. The generated hydrogen ions (H ⁺ ) move in the direction of the lower electrode 110 by an electric field inside the magnetic memory device 1.

Metal such as Au may be used for the upper electrode 140. Depending on the embodiment, the upper electrode 140 may be formed of a material that easily decomposes water among metals. For example, the upper electrode 140 may be formed of any one or at least two compounds among Cu, Pt, and Ir.

3 is a diagram illustrating an example of the oxide layer 130 of FIG. 1.

Since the oxide layer 130 is a path through which hydrogen ions generated in the upper electrode 140 travel, the ionic conductivity needs to be high in order to increase the switching speed of the magnetic memory device 1. Accordingly, the oxide layer 130 may be made of a material having an open grid structure. As the oxide layer 130, for example, a rare earth oxide may be used. One can be used.

It is preferable that the thickness of the oxide layer 130 is thin in order to improve the switching speed. The thickness of the oxide layer 130 may be, for example, about 5 nm.

4 is a diagram illustrating a magnetic memory device 1'according to an embodiment of the present invention.

Referring to FIG. 4, the magnetic memory device 1 ′ further includes an antioxidant layer 150 between the magnetic material layer 120 and the oxide layer 130 compared to the magnetic memory device 1 of FIG. 1. The antioxidant layer 150 may be made of, for example, Pd.

According to this embodiment, since the magnetic material layer 120 does not directly contact the oxide layer 130, oxidation of the magnetic material layer 120 can be prevented. Accordingly, since it becomes possible to apply a-voltage, rapid release of hydrogen ions is possible.

5 is a diagram for explaining the operation of the magnetic memory devices 1 and 1'according to an embodiment of the present invention. In FIG. 5, only the lower electrode 110 and the magnetic material layer 120 are shown to cover all of the magnetic memory devices 1 and 1 ′. The left side of FIG. 5 shows a case where +6V is applied between the upper electrode 140 and the lower electrode 110, and the right side of FIG. 5 shows -6V between the upper electrode 140 and the lower electrode 110. It indicates the case of application.

5, when +6V is applied between the upper electrode 140 and the lower electrode 110, hydrogen ions (H ⁺ ) generated in the upper electrode 140 move toward the lower electrode 110 It is distributed at the interface between the magnetic material layer 120 and the lower electrode 110. When -6V is applied between the upper electrode 140 and the lower electrode 110, hydrogen ions (H ⁺ ) distributed at the interface between the magnetic material layer 120 and the lower electrode 110 are transferred to the upper electrode 140. ^{By moving, hydrogen ions (H +} ) at the interface between the magnetic material layer 120 and the lower electrode 110 decrease.

6 and 7 show experimental results of a magnetic memory device according to an embodiment of the present invention. In this experiment, the magnetic memory device 1'of FIG. 4 was used, a Pd layer was used as the lower electrode 110, a Co layer was used as the magnetic material layer 120, and a Pd layer was used as the antioxidant layer 150. Is used, YSZ having a thickness of 5 nm is used as the oxide layer 130, and Pt is used as the upper electrode 140.

6 is a graph showing changes in magnetic anisotropy of the magnetic memory element 1'. The left side of FIG. 6 shows a case where +6V is applied between the upper electrode 140 and the lower electrode 110, and the right side of FIG. 6 shows -6V between the upper electrode 140 and the lower electrode 110. It indicates the case of application.

As shown in FIG. 6, it can be seen that a change in magnetic anisotropy appears as the voltage applied between the upper electrode 140 and the lower electrode 110 is reversed.

7 is a graph showing _{a magnetization ratio (M r} /M _s ) of the magnetic memory device 1 according to an exemplary embodiment of the present invention. In FIG. 7, a voltage of +6V and a voltage of -6V were switched between the upper electrode 140 and the lower electrode 110 at 0.5Hz.

As shown in FIG. 7, when the voltage between the upper electrode 140 and the lower electrode 110 was inverted, a change in the magnetization ratio accordingly was also observed at the same speed.

In fact, it was confirmed that the magnetic memory device 1'according to the embodiment of the present invention has a switching time less than 1 ms, which is a measurable resolution, and a cyclability greater than ^{10 3.} This is the fastest speed among the research results reported so far in controlling magnetic anisotropy by moving ions through voltage control.

8 is a diagram illustrating a magnetic memory device according to an embodiment of the present invention. The magnetic memory device operates in a spin orbit torque (SOT) method including the magnetic memory device 1 ′ of FIG. 4. 8 illustrates that the magnetic memory device 1 ′ is included, the anti-oxidation layer 150 may be omitted, but may be implemented to include the magnetic memory device 1.

Referring to FIG. 8, the gate terminal #0 is connected to the upper electrode 140 of the magnetic memory device, and the first to fourth terminals #1 to #4 are connected to the cross-shaped lower electrode 110. do.

The operation of such a magnetic memory device is as follows.

_{First, a gate voltage V G} is applied between the gate terminal #0 and the first terminal #1 (Stage 1). Accordingly, an electric field is formed across the oxide layer 130, and hydrogen ions induced by the voltage change the magnetic anisotropy of the magnetic layer 120.

Next, a short (nanosecond unit) current pulse is applied (the switching voltage Vsw is turned on), and a spin current is induced by the spin lobe torque that applies a torque for switching (Stage 2).

Next, as soon as the magnetization is switched to the opposite state, the gate voltage V _G and the switching voltage Vsw are turned off to maintain the magnetic data in a high anisotropic state, which is usually stable against thermal fluctuations.

As described above, the present invention has been described in detail through preferred embodiments, but the present invention is not limited thereto, and various changes and applications can be made without departing from the technical spirit of the present invention. It is self-explanatory to the technician. Therefore, the true scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Claims (8)

A cross-shaped, formed at four ends of the cross-shaped, a first terminal, a second terminal formed at a position facing the first terminal, a third terminal, and a fourth formed at a position facing the third terminal A lower electrode on which a terminal is formed;
A magnetic layer formed on the cross-shaped cross portion of the lower electrode;
An oxide layer formed on the magnetic layer and having an open lattice structure; And
An upper electrode formed on the oxide layer;
A method of driving a magnetic memory device comprising:
Applying a gate voltage between the upper electrode and the first terminal of the lower electrode, whereby moisture around the upper electrode is decomposed to generate hydrogen ions, and the magnetic anisotropy of the magnetic layer is changed by the generated hydrogen ions;
Generating a current in the lower electrode by applying a switching voltage between the first and second terminals of the lower electrode, thereby inducing a spin trajectory torque for switching the magnetization of the magnetic layer; And
Maintaining the switched magnetization state by turning off the gate voltage and the switching voltage.
A method of driving a magnetic memory device comprising: a.
The method of claim 1,
The method of driving a magnetic memory device, wherein the oxide layer is a rare earth oxide.
The method of claim 2,
The oxide layer is a method of driving a magnetic memory device, comprising any one of Yttria-Stabilized Zirconia (YSZ), Barium Cerium Yttrium Zirconate (BZCY), and Gadolinium-doped Ceria (GDC).
The method of claim 1,
A driving method of a magnetic memory device, further comprising an antioxidant layer formed between the magnetic layer and the oxide layer to prevent oxidation of the magnetic layer.
The method of claim 4,
The method of driving a magnetic memory device, wherein the antioxidant layer is made of Pd.
The method of claim 1,
The upper electrode is a driving method of a magnetic memory device, characterized in that made of any one or at least two compounds of Cu, Pt, and Ir.


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