KR101164888B1 - Apparatus and method for writing data - Google Patents

Abstract

An embodiment relates to a data writing apparatus.
The data writing apparatus according to the embodiment relates to an apparatus for writing data into a magnetic line element having perpendicular magnetic anisotropy (PMA), and is oblique to a width direction of the magnetic line element, and has a length of the magnetic line element. And a current applying unit configured to apply current so that currents in opposite directions flow through the first conductive wire and the second conductive wire and the first conductive wire and the second conductive wire which are arranged at a predetermined interval in the direction.

Description

Data writing device and writing method {APPARATUS AND METHOD FOR WRITING DATA}

An embodiment relates to a data writing apparatus and a writing method.

Ferromagnetic materials are applied to information storage and are used as various memory devices. Recently, active studies on the change of magnetization state using current have revealed that the magnetization state can be changed by passing a current through the ferromagnetic device.

Interaction occurs between spins of electrons and spins of atoms flowing by electric current. Such a phenomenon is used to change the magnetization state of the ferromagnetic element, and is called spin transfer torque (STT) because angular momentum is exchanged between electrons and atoms.

Recently, various devices using spin transfer torque have been proposed. Among them is IBM's proposed race track memory. Racetrack memory has a feature of storing information using a magnetic domain in a ferromagnetic nanowire device. Ferromagnetic nanowires used in racetrack memories are classified into nanowires having in-plane magnetic anisotropy (IMA) and perpendicular magnetic anisotropy (PMA) according to their magnetic properties. Nanowire devices usually have a thickness from several A to several nm, with widths of several hundred nm. The nanowire device is said to have horizontal magnetic anisotropy if the magnetization state in the longitudinal direction is preferred, and vertical magnetic anisotropy if the magnetization state is easily formed in the thickness direction.

1 is a diagram illustrating a racetrack memory 10 for storing information according to horizontal magnetic anisotropy. 2 shows a racetrack memory 20 for storing information according to perpendicular magnetic anisotropy.

As shown in FIGS. 1 and 2, when information of “1” or “0” is stored in the form of magnetic domain, a magnetic domain wall is formed in the boundary region in which the magnetization direction of the magnetic domain is changed. The magnetic domain wall means an area in which the magnetization direction gradually changes from the magnetization direction of one magnetic domain to the magnetization direction of another adjacent magnetic domain.

FIG. 3 is a diagram illustrating four magnetic domain wall shapes that may exist in a magnetic line device having perpendicular magnetic anisotropy.

Since the magnetization amount is always preserved when the temperature is constant, the magnetic domain walls have a magnetization state in a direction away from the magnetization direction preferred by the nanowires. In particular, the magnetic domain walls formed from nanowires having perpendicular magnetic anisotropy may have four forms (+ y blot, -y bloch, -x niel, + yl) as shown in FIG.

The magnetic domain wall is determined by the width and thickness of the magnetic nanowire device. The thinner and smaller the nanowire element is, the more the Bloc magnetic domain wall is formed. Since the thickness of the PMA wire element is several nm to several nm and the width is several hundred nm, the magnetic domain wall is always formed in the form of the Bloch magnetic domain wall. The magnetization direction of the wall may have two directions, + y and -y.

4 is a diagram illustrating information loss <A3> of a racetrack memory due to an increase in information density and a magnetic domain wall merging phenomenon <A2> as the length of the magnetic domain decreases.

The magnetic domain walls serve to distinguish each bit. Therefore, reducing the spacing between the magnetic domain walls reduces the size of the unit bits, it is possible to store more information in the same length.

However, when the distance between the magnetic domain walls gets closer, that is, the length of the magnetic domain is shortened <A2>, the energy becomes unstable because two magnetic domain walls exist in a narrow space. As a result, the phenomenon that the magnetic domain disappears as the magnetic domain walls merge with each other occurs.

Embodiments provide an apparatus and a method capable of preventing the magnetic domain wall from being merged when the magnetic domain and the magnetic domain wall are formed in the magnetic line element.

The data writing apparatus according to the embodiment relates to a device for writing data to a magnetic line element having perpendicular magnetic anisotropy, which is oblique to the width direction of the magnetic line element and is arranged at a predetermined interval in the longitudinal direction of the magnetic line element. And a current applying unit configured to apply current so that currents in opposite directions flow through the first and second conductive wires, and the first and second conductive wires.

A data writing apparatus according to another embodiment relates to an apparatus for writing data into a magnetic line element having perpendicular magnetic anisotropy, and comprising: a magnetic insulating layer disposed on a magnetic line element and a magnetic insulating layer disposed on the magnetic line element. And a current applying unit configured to apply a current so that current flows from the magnetic wire element through the magnetic insulating layer to the fixed magnetic layer.

The data writing method according to the embodiment relates to a method of writing data into a magnetic line element having perpendicular magnetic anisotropy, wherein two conductors are oblique to the width direction of the magnetic line element, and are fixed in the longitudinal direction of the magnetic line element. Arranging at intervals, and applying current so that currents in opposite directions flow through the two conductive wires.

A data writing method according to another embodiment relates to a method of writing data into a magnetic line element having perpendicular magnetic anisotropy, comprising: disposing a magnetic insulating layer on the magnetic line element, and arranging a pinned magnetic layer on the magnetic insulating layer. The method may further include disposing the magnetic wire element perpendicularly to the longitudinal direction of the magnetic wire element, and applying a current so that the current flows from the magnetic wire element through the magnetic insulating layer to the fixed magnetic layer.

According to the embodiment, it is possible to provide an apparatus and a method capable of preventing the magnetic domain wall from being merged when the magnetic domain and the magnetic domain wall are formed in the magnetic wire element.

1 illustrates a race track memory for storing information according to in-plane magnetic anisotropy (IMA).
FIG. 2 is a diagram of a racetrack memory for storing information in accordance with a perpendicular magnetic anisotropy (PMA). FIG.
3 is a view showing four magnetic domain wall shapes that may exist in a magnetic line element having perpendicular magnetic anisotropy.
4 is a diagram illustrating information loss of a racetrack memory due to an increase in information density according to a decrease in the length of a magnetic domain and a merger phenomenon of the magnetic domain walls;
FIG. 5 is a diagram showing imaginary experimental results for showing how well the magnetic domain walls merge according to the polarity of the magnetic domain walls. FIG.
6 illustrates a general method of writing data into a magnetic line element using current.
FIG. 7 is a side view of the phenomenon shown in FIG. 6; FIG.
8 is a view showing a method of writing data in a magnetic element using a slanted conductive line, polarity of the magnetic domain wall and polarization rotation phenomenon.
Fig. 9A shows a data writing apparatus and a writing method according to the first embodiment.
9B is a view showing phantom experimental results for showing a process of forming a domain and a domain wall according to the first embodiment.
Fig. 10A is a diagram showing a data writing apparatus and a writing method according to the second embodiment.
FIG. 10B is a view showing a spin transfer torque phenomenon according to a second embodiment and a magnetic domain and a magnetic domain wall formed in a magnetic wire element by the phenomenon; FIG.

Hereinafter, prior to the detailed description of the embodiments will be briefly described the problem to be solved by the present invention and the basic principles of the present invention.

The phenomenon that the magnetic domain disappears due to the merged magnetic domain wall is highly dependent on the polarity of the magnetic domain wall.

FIG. 5 is a diagram showing an imaginary experiment result to show how well the magnetic domain walls merge according to the polarity of the magnetic domain walls. <B1> shown in FIG. 5 is a case where the magnetic domain walls are formed with opposite polarities, and <B2> is a case where the same polarity is formed.

When a magnetic domain having a magnetization state in the + z direction (+ Ms) is made to a part of the magnetic element in which the magnetization states are aligned in the -z direction (-Ms), and an external magnetic field in the -z direction (-Ms) is applied The length of the domain becomes shorter and shorter. As the length of the domain decreases, the energy becomes unstable for two domain walls in a narrow space. As the length of the magnetic domain decreases gradually and the external magnetic field becomes the threshold value, the two magnetic domain walls can no longer exist together at a close distance. As a result, the two magnetic domain walls are merged to cause the magnetic domain to disappear, resulting in the loss of information stored in the magnetic element.

As shown in FIG. 5, in the case of <B2> having the same polarity of the magnetic domain walls, an external magnetic field of 29Oe is required to combine the magnetic domain walls, but in the case of <B1> having the opposite polarities, the 140Oe An external magnetic field is needed. In other words, if the polarities of two adjacent magnetic domain walls are opposite to each other, there may be a magnetic domain having a much shorter distance between the magnetic domain walls.

Accordingly, it can be seen that the magnetic domain walls can be further reduced by reducing the length of the magnetic domains than when the polarities of the magnetic domain walls are opposite to each other.

FIG. 6 is a diagram illustrating a general method of writing data into the magnetic line elements 20 using current. FIG. 7 is a side view illustrating the phenomenon shown in FIG. 6.

One of the methods used to write magnetic domains in a magnetic wire element is a method using a magnetic field generated in a conductive wire through which current flows. 6 and 7, the magnetic field generated when the conductive wire 30 is disposed in the width direction of the magnetic wire element 20 and a current 31 is flowed through the conductive wire 30. It is a method of forming magnetic domains.

6 and 7, when the angle between the magnetic line element 20 and the conductive line 30 is perpendicular, the polarity of the magnetic domain wall may not be determined. The reason is that the polarity of the magnetic domain wall is determined by the magnetic field in the width direction given from the outside when the magnetic domain wall is made. When the magnetic line element 20 and the conductive wire 30 are perpendicular to each other, the magnetic field in the width direction is This is because only a magnetic field in the longitudinal direction is generated, not generated. In addition, the polarity of the two magnetic domain walls in this situation is determined randomly by the thermal fluctuation phenomenon.

FIG. 8 is a diagram illustrating a method of writing data into the magnetic line element 20 using the inclined conductive line 30, the polarity of the magnetic domain wall, and the polarity rotation phenomenon.

The method illustrated in FIG. 8 is a method for reducing random effects due to temperature, and is a method of making the angle θ formed by the magnetic line element 20 and the conductive line 30 slightly out of the vertical direction. At this time, among the magnetic domain walls formed on the magnetic wire element 20, the magnetic domain wall a formed below the conductive wire 30 has a magnetic field in the width direction of the magnetic wire element 20, so that the polarity of the magnetic domain wall is increased. Can be determined. However, the magnetic domain wall b formed on the outside of the conductive wire 30 is moved by the magnetic field as soon as it is formed. In this way, the moving magnetic domain wall b has a phenomenon called 'Walker break down'. This phenomenon is a phenomenon in which the polarity of the moving magnetic domain wall is continuously rotated.

As a result, in order to determine the polarity of the magnetic domain wall, a current pulse length of several picoseconds should be possible. However, controlling the time for passing the current to several ps is practically difficult and is greatly influenced by random phenomena caused by temperature fluctuations or slight non-uniformity present in the magnetic element.

Hereinafter, in the case of forming magnetic domains and magnetic domain walls (when data is written) in a magnetic line element having perpendicular magnetic anisotropy, two adjacent adjacent ones are not sensitive to the effects of thermal fluctuation and current application time. A data writing apparatus and a method of forming a magnetic domain so that the polarities of the magnetic domain walls are opposite to each other will be described in detail.

[data Writing device  One]

9A is a diagram showing a data writing apparatus 900 and a writing method according to the first embodiment.

Referring to FIG. 9A, the data writing apparatus 900 according to the first embodiment may include a first conductive line 921, a second conductive line 923, and a current applying unit 930.

The first conductive line 921 and the second conductive line 923 may be disposed in parallel with each other above or below the magnetic wire element 920. In addition, the first conductive wire 921 may be disposed above the magnetic wire element 910, the second conductive wire 923 may be disposed below the 910 of the magnetic wire element, and the first conductive wire 921 may be disposed on the magnetic wire element 910. The second conductive line 923 may be disposed below the magnetic line element 910 and may be disposed above the 910 of the magnetic line element.

The first conductive line 921 and the second conductive line 923 may be disposed at regular intervals G in the longitudinal direction of the magnetic wire element 910. The distance G determines the size of the unit bit (magnitude of the magnetic domain), and the longer the time when the magnetic domain walls formed outside the conductors merge with each other, the longer the interval G between the conductors becomes. Therefore, it is preferable to set the space | interval between the 1st conducting wire 921 and the 2nd conducting wire 923 short enough.

In addition, the first conductive line 921 and the second conductive line 923 are disposed to have a predetermined angle θ that is not 0 degrees with respect to the width direction of the magnetic line element 910. That is, the first conductive line 921 and the second conductive line 923 should be disposed obliquely with respect to the width direction of the magnetic wire element 910. When the conducting wires are disposed at an angle of 45 degrees with the magnetic wire elements 910, respectively, the magnetic field in the width direction of the magnetic wire elements 910 may be maximized to accurately determine the polarity of the magnetic domain walls. However, as the angle θ of the conducting wire approaches 0 degrees to 90 degrees, the length of the magnetic domain formed by that length becomes longer. Therefore, the angle θ of the conductive wire may be an angle greater than 0 degrees within a range such that the magnetic field in the width direction minimizes the effect of thermal fluctuation and determines the polarity of the magnetic domain wall.

The current applying unit 930 is connected to the first conductive line 921 and the second conductive line 923, and applies current so that the directions of the currents flowing in the first conductive line 921 and the second conductive line 923 are opposite to each other. do.

[data Writing device  Data of 1 How to fill in ]

Hereinafter, a data writing method of the data writing apparatus 900 according to the first embodiment, that is, a method of creating a desired magnetization state will be described.

First, currents in opposite directions flow through the current applying unit 930 through the first conductive line 921 and the second conductive line 923. When currents in opposite directions flow through the first and second conductive lines 921 and 923, magnetic domains and magnetic domain walls are formed in the magnetic line elements 910. At this time, one magnetic domain and two magnetic domain walls are made by one conductive wire.

Here, the magnetic domain walls formed between the first conductive line 921 and the second conductive line 923, that is, the outer side of the first conductive line 921 and the outer side of the second conductive line 923 have different polarities. However, as the magnetic fields generated between the first conductive line 921 and the second conductive line 923 are added together, a strong magnetic field is generated, and the first conductive line 921 and the second conductive line ( The two magnetic domain walls created between 923 are joined together.

The magnetic domain walls respectively formed below the first conductive line 921 and the second conductive line 923 are stably fixed below the conductive line while a current flows through the conductive line. This is because the magnetic field in the z direction is reversed with respect to the left and right of the conductor. While the magnetic domain wall is fixed, the magnetic domain wall is formed in a shape in which the Bloch magnetic domain wall and the Neil magnetic domain wall are combined.

 The magnetic domain walls remaining below the first conductive wire 921 and the second conductive wire 923 are determined by the widthwise components of the magnetic wire element 910. Accordingly, when no current is applied to the first conductive line 921 and the second conductive line 923, the magnetic domain walls having opposite polarities remain below the first conductive line 921 and the second conductive line 923.

FIG. 9B is a diagram illustrating a virtual experiment result for illustrating a process of forming a domain and a domain wall according to the first embodiment. -Ms shown in FIG. 9B means magnetization in the -z direction, and + Ms means magnetization in the + z direction.

FIG. 9B is a magnetic field generated when an angle formed by a width direction of a conductive line and a magnetic line element is set to about 15 degrees, and currents in opposite directions flow through the two conductive lines, respectively. It shows how it is formed.

As shown in FIG. 9B, when the time of applying the current is 0.08 ns, the magnetic domain is formed, when the magnetic domain wall outside the conductor moves at 0.16 ns, and the magnetic domain wall outside the conductor is combined at 0.26 ns. At 0.76 ns, the magnetic domain wall is stabilized against the magnetic field. Thereafter, when the current application is stopped, the polarities of the magnetic domain walls are aligned, and the polarities of the two magnetic domain walls formed are opposite to each other. That is, as shown in FIG. 9B, when the magnetic domain in the + z direction is formed, the magnetic domain wall in the -y direction is formed on the left side of the magnetic domain in the + z direction, and the magnetic domain wall in the + y direction is formed on the right side.

In addition, if the directions of the currents between the two conductors are reversed, a magnetic domain in the -z direction is formed, a magnetic domain wall in the + y direction is formed on the left side of the magnetic domain in the -z direction, and a magnetic domain wall in the -y direction is formed on the right side. Can be. Therefore, the directions of the magnetic domain walls formed on both sides are always opposite to each other according to the direction of the magnetic domains to be formed, and the magnetic domains in the + z direction and the magnetic domains in the -y direction can be stably attached to each other.

According to the embodiment, as shown through the virtual experimental results, the data can be written by stably forming the magnetic domain and the magnetic domain wall.

In the case where data is written into the magnetic line element according to the first embodiment, that is, when the magnetic domain and the magnetic domain wall are formed, it is preferable to satisfy the following conditions.

First, the magnitude of the magnetic field generated by the current flowing in the conductive wire should be large enough to change the magnetization state of the magnetic wire element.

Second, the current flowing through the wire should be long enough to merge the magnetic domain walls formed outside the wire. After the time enough for the two magnetic domain walls formed between the two conductors to merge, the time is not important.

Third, the distance between the two leads should be short enough. Since the distance between the two wires ultimately determines the size of one bit, and the time that the magnetic domain walls formed outside the wires merge with each other becomes longer as the distance between the wires increases, it is better to arrange the two wires close to each other.

Fourth, the two conductive wires should be arranged obliquely with respect to the width direction of the magnetic wire element, and should not be arranged to be 0 degrees with respect to the width direction of the magnetic wire element.

Fifth, the direction of the current flowing in the two leads should be reversed.

[data Writing device  2]

The second embodiment relates to an apparatus and method for writing data into a magnetic element using a spin torque writing method, and more particularly, to an apparatus and method for making polarities of two adjacent magnetic domain walls opposite to each other. . This spin torque write method utilizes a spin transfer torque (STT) phenomenon. STT means that the magnetization state is transmitted by the flowing electrons.

10A is a diagram showing a data writing apparatus 1000 and a writing method according to the second embodiment. FIG. 10B is a view illustrating magnetic domains and magnetic domain walls formed in the magnetic line element 1100 by the STT phenomenon and the STT phenomenon according to the second embodiment.

Referring to FIG. 10A, the data writing apparatus 1000 according to the second embodiment may include a magnetic insulating layer 1200, a pinned magnetic layer 1300, and a current applying unit 1400.

The magnetic insulating layer 1200 may be disposed on the magnetic line element 1100. The magnetic insulating layer 1200 may have a thickness of a number A and may serve as a spacer between the pinned magnetic layer 1300 and the magnetic line element 1100.

The pinned magnetic layer 1300 may be disposed on the magnetic insulating layer 1200, and may be disposed perpendicularly to the length direction of the magnetic line element 1100. The pinned magnetic layer 1300 is referred to as a 'fixed layer' because the magnetization state is not changed, and on the contrary, the magnetic line device 1100 is also referred to as a 'free layer' because the magnetization state may be changed.

The current applying unit 1400 may allow a current to flow from the magnetic wire element 1100 to the stator magnetic layer 1300 through the magnetic insulating layer 1200.

[data Writing device  2 data How to fill in ]

The data writing method according to the second embodiment will be described below.

First, when a current is applied through the current applying unit 1400, a current flows from the magnetic wire element 1100 to the staging magnetic layer 1300 through the magnetic insulating layer 1200. That is, a movement path of electrons is formed from the stator magnetic layer 1300 toward the magnetic line element 1100. Accordingly, the magnetization state of the side of the pinned magnetic layer 1300 is transferred toward the magnetic line element 1100, thereby changing the magnetization state of the region of the magnetic line element 1100 below the magnetic insulation layer 1200.

In general, the magnetic direction of ferromagnetic materials is determined by the spin direction of electrons in the 3D orbital. In addition, current flow means that free electrons are moved by applying an electric field from the outside. When current flows in this way, the spin of the electron and the spin of the 3D opal electron of the ferromagnetic material interact with each other to give an alignment force. Will receive. If the magnetization direction of the pinned magnetic layer 1300 is determined, the spin direction of flowing electrons is aligned with the magnetization direction of the pinned magnetic layer 1300. When electrons having aligned spins pass through the magnetic insulating layer 1200 and enter the magnetic line device 1100, the spin of the flowed back electrons and the spins of electrons of the three-dimensional optal of the magnetic line device 1100 are aligned with each other. The phenomenon occurs. Accordingly, a force is applied to turn the magnetization direction of the magnetic wire element 1100. Therefore, a phenomenon in which the magnetization state of the pinned magnetic layer 1300 is transferred toward the magnetic line device 1100 is generated through electrons flowing therethrough.

Since the data writing apparatus 1000 according to the second exemplary embodiment has a structurally stacked structure, a vertical current is generated by the magnetic insulating layer 1200 disposed between the pinned magnetic layer 13300 and the magnetic line element 1100. Done. Accordingly, as shown in FIG. 10B, the magnetic field 12 that is rotated by the current in the vertical direction is formed in the region C of the magnetic line element 1100 below. The polarity of the two magnetic domain walls (A, B) formed on both sides of the magnetic domain (C) by the rotating magnetic field 12 may be opposite to each other.

As described above, the embodiment has been described in detail by applying to the apparatus and method for writing data by forming the magnetic domain and the magnetic domain wall in the magnetic wire element, but is not limited to this, those skilled in the art to which the present invention belongs It will be appreciated that the invention can be practiced as an apparatus and method for controlling the polarity of magnetic domain walls without changing the technical spirit or essential features.

Therefore, the embodiments described above are to be understood in all respects as illustrative and not restrictive, and the scope of the present invention is indicated by the following claims rather than the above description, and the meaning and scope of the claims And all changes or modifications derived from the equivalent concept should be interpreted as being included in the scope of the present invention.

Claims (7)

The present invention relates to an apparatus for writing data in a magnetic line element having perpendicular magnetic anisotropy,
First and second conductive wires intersecting the width direction of the magnetic wire element and disposed at regular intervals in the longitudinal direction of the magnetic wire element; And
And a current applying unit configured to apply current to the first conductive line and the second conductive line so that currents in opposite directions flow.
The method of claim 1,
And the first conductive wire and the second conductive wire are arranged at an angle of 45 degrees with the width of the magnetic wire element.
delete A method of writing data in a magnetic line element having perpendicular magnetic anisotropy,
Arranging two conductive wires at an interval with respect to the width direction of the magnetic wire element, and spaced apart from each other in the longitudinal direction of the magnetic wire element; And
And applying current to the two conductive wires so that currents in opposite directions flow.
The method of claim 4, wherein
And the two conductive wires are arranged at an angle of 45 degrees with respect to the width direction of the magnetic wire element.
delete The method of claim 4, wherein
And after the data writing is completed on the magnetic line elements, polarities of two adjacent magnetic domain walls among magnetic domain walls formed on the magnetic line elements are opposite to each other.

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