JPS6337888A - Bloch line memory - Google Patents

Abstract

PURPOSE:To attain excellent Bloch line transfer with simple constitution by forming a plane form of a part of a ridge of a magnetic substance layer in a periodic rugged shape having directivity along a magnetic wall and crossing the magnetic wall. CONSTITUTION:A magnetic thin film 4 is formed on a substrate 2. A magnetic domain 6 having a stripe shape is formed in the film 4. A magnetic wall 8 is formed around the magnetic domain 6. A magnetic substance layer 12 is formed on a region corresponding nearly to the magnetic domain 6 on the surface of the film 4. The layer 12 has an axis for easy magnetization in the direction of (x) and is magnetized clockwise. Both edges relating to the direction (y) of the layer 12 form symmetrical sawtooh shapes and overlapped partially with the magnetic wall 8. Through the constitution above, when a pulse magnetic field is applied downward in the film broadwise direction of the film 4, paired Bloch lines are moved to the right at the part 8a and to the left at the part 8b. Through the constitution above, since the Bloch line is transferred surely to a specific direction by the application of a simple square pulse magnetic field, a simple electric circuit is enough for the purpose.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to Bloch line memories. Bloch line memory is a memory that can record information at extremely high density and can be applied to various types of installed stones.

[Prior Art] At present, memories such as external memory for computers, memory for electronic files, and memory for still image files include magnetic tape, Winchester disk, floppy disk, optical disk, magneto-optical disk, magnetic bubble memory, etc. Various types of memory devices are used. Among these memory devices, other than the magnetic bubble memory, it is necessary to move the recording/reproducing head relative to the memory when recording or reproducing information. That is,
With such relative movement of the head, the head records an information string fixedly on the information track or reproduces the information string fixedly recorded on the information track.

However, in recent years, as there has been a demand for increasingly higher recording densities, tracking control to make the head accurately follow the information track has become more complex, and the quality of recorded and reproduced signals may deteriorate due to insufficient control. The quality of recorded and reproduced signals may deteriorate due to vibrations in the head moving mechanism and dust attached to the surface of the memory, and in the case of memories that are recorded and reproduced while coming into contact with heads such as magnetic tape, sliding When wear occurs, and in the case of a memory that performs recording and reproduction without contact with the head, such as an optical disk, focusing control is required for focusing, and because this control is insufficient, the quality of the recording and reproduction signal may deteriorate. There is a problem of doing so.

On the other hand, magnetic bubble memory can record information at a predetermined position and transfer the recorded information, and can reproduce information at a predetermined position while transferring the information, and when recording and reproducing, the head and It is believed that the above-mentioned problems do not occur even when the recording density is increased, and that high reliability can be achieved.

However, magnetic bubble memory uses circular magnetic domains (bubbles), which are generated by applying a magnetic field to a magnetic thin film such as a magnetic garnet film, whose axis of easy magnetization is perpendicular to the film surface, as information bits. Garnet)
The minimum bubble (diameter 0.3
Even if the recording density is used, the limit of the recording density is several tens of Mbits/CrrI', and it is difficult to further increase the density.

Therefore, recently, Bloch line memory has been attracting attention as a memory having a recording density that exceeds the recording density limit of the above-mentioned magnetic bubble memory. This Bloch line memory is
Because it uses a pair of Neel 5m wall structures (Bloch lines) sandwiched between Bloch domain wall structures that exist around magnetic domains generated in a magnetic thin film as information bits, it has a recording capacity of nearly two orders of magnitude compared to the above &a magnetic bubble memory. It is possible to increase the density. For example, when using a garnet film with a bubble diameter of 0.5 gm, it is possible to achieve a recording density of 1.6 Gbit/ctn' [[Nikkei Electronics 4, August 15, 1983, P141 N167
reference].

FIG. 6 shows a schematic perspective view of an example of a magnetic structure constituting the Bloch line memory.

In the figure, 2 is a substrate made of non-magnetic garnet such as GGG, NdGG, etc., and a magnetic garnet thin film 4 is provided on the substrate. The film can be formed by, for example, a liquid phase epitaxial growth method (LPE method), and its thickness is, for example, about 5 ALm. 6 is a striped magnetic domain formed in the magnetic garnet thin film 4, and a domain wall 8 is formed as an inner and outer boundary region of the magnetic domain.

The width of the striped magnetic domain 6 is, for example, about 5 μm, and the length is, for example, about 100 m. Further, the thickness of the &a domain wall is, for example, about 0.5 gm. As shown by the arrows, the direction of magnetization is upward within the magnetic domain 6, while the direction of magnetization is downward outside the magnetic domain 6.

The direction of magnetization within the domain wall 8 gradually rotates from the inner surface (that is, the surface facing the magnetic domain 6) to the outer surface in a twisted manner.

The direction of this rotation is opposite on both sides of the Bloch line 10 that is perpendicular to the domain wall 6 as a boundary. 6th
In the figure, the direction of magnetization at the center in the thickness direction of the +a domain wall is indicated by an arrow, and the direction of magnetization at the Bloch line 10 is similarly indicated.

Note that a downward bias magnetic field HB is applied to the above-described magnetic structure from the outside.

As illustrated, there are two types of Bloch lines 10 with different magnetization directions, and the presence or absence of a pair of these Bloch lines corresponds to information "1" and "0". The Bloch line pair exists at regular positions in the domain wall 8, that is, at any one of the potential wells. Further, each Bloch line pair is sequentially transferred to an adjacent potential well by applying a pulsed magnetic field perpendicular to the substrate surface. Thus, the recording of information to the Bloch line memory (writing of Bloch 2 Holt line pairs to the domain wall 8) and the reproduction of the information recorded in the Bloch line memory (reading of the Bloch line pair in the domain wall 8) are performed using the Bloch line memory. This can be carried out at a predetermined position l while transferring the pairs within the domain wall 8. The above information can be recorded and reproduced by applying a pulsed magnetic field of a predetermined strength perpendicular to the substrate surface to a predetermined portion.Although not shown in FIG. As a means for applying a pulsed magnetic field for reproduction, conductive patterns for pulsed current application are formed on the surface of the magnetic thin film 4 at predetermined positional relationships with respect to the striped magnetic domains 6, respectively.

[Problem to be solved by the invention 1 However, in the Bloch line memory as described above,
The potential wells for the Bloch line pairs are formed, for example, by providing a regular pattern on the surface of the magnetic thin film so as to cross the domain wall.

FIG. 7 is a partial plan view of a Bloch line memory showing an example of such a pattern.

In the figure, on the surface of the magnetic thin film 4, a large number of line-shaped patterns 9 extending in a direction across the striped magnetic domains 6 are provided in parallel. The pattern may be, for example, Cr,
Consists of conductor layers such as A I , A u , T i , etc.
Its width is, for example, about 0.5 Bm, and the array pea of 2,000 is, for example, about Igm. Due to the distortion caused by the formation of the patterned conductor layer, the potential wells within the domain wall 8 can be arranged regularly and periodically.

Further, as the pattern 9, in addition to the conductor layer, for example, a magnetic layer, or a material in which ions such as H ions, He ions, Ne ions, etc. are implanted in the pattern shape near the surface of the magnetic thin film 4 is used. You can also do that. Each potential well formed by these patterns is symmetrical with respect to the Bloch line transfer direction.

By the way, as mentioned above, Bloch line transfer is achieved by applying a pulsed magnetic field perpendicular to the film surface of the magnetic G film 4, and using the precession of magnetization generated by this to transfer the voltage to the adjacent potential well. This is done by moving the However, in the case of a symmetrical potential well like the one described above, it is not possible to stably move it in a specific direction by using a simple rectangular pulsed magnetic field as the pulsed magnetic field. As the pulsed magnetic field HP for Bloch line transfer, a pulsed magnetic field having a shape in which the fall time is sufficiently larger than the rise time is used, thereby ensuring irreversible transfer in a specific direction.

For this reason, the electrical circuit for generating a pulsed magnetic field is more complicated than in the case of generating a rectangular pulsed magnetic field, and since the fall time is long, it is difficult to improve the transfer speed, and the power consumption also increases. There was a point.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the problems of the conventional Bloch line memory as described above, and to provide a Bloch line memory that can realize stable, high-speed, and good Bloch line transfer with a simple configuration. do.

[Means for Solving the Problems] According to the present invention, in order to achieve the above-mentioned objects, information is recorded using blow two holes in domain walls formed around magnetic domains in a magnetic thin film. In the Bloch line memory to be carried out, a magnetic layer is partially formed on the Ia-based film, and the planar shape of at least a part of the edge of the magnetic layer crosses the domain wall and extends in one direction along the domain wall. A Bloch line memory is provided which is characterized in that it has a periodic uneven shape with a certain characteristic.

[Example] Hereinafter, specific examples of the present invention will be described with reference to the drawings.

FIG. 1(a) is a partial plan view of a Bloch line memory according to the present invention, and FIG. 1(b) is a sectional view thereof taken along line B--B.

In FIG. 1, 2 is a non-magnetic garnet substrate, and 4 is a non-magnetic garnet substrate.
is a magnetic garnet thin film. Magnetic domains 6 having a striped planar shape are formed in the magnetic garnet thin film. 8 is a domain wall around the striped magnetic domain 6.

The direction of magnetization within the striped magnetic domain 6 is upward, and the direction of magnetization in the portion of the magnetic thin film 4 outside the magnetic domain is downward. Further, a downward bias magnetic field is applied from the outside.

A ferromagnetic layer 12 is formed on the surface of the magnetic l film 4 in a region substantially corresponding to the striped magnetic domains 6. The ferromagnetic layer is made of, for example, a thin layer of CoPt or the like, and its thickness is, for example, about 0.1 μLm. The ferromagnetic layer 12 has an axis of easy magnetization in the X direction and is magnetized to the right.

As shown in FIG. 1(a), both end edges of the ferromagnetic layer 12 in the X direction have a symmetrical sawtooth shape and partially overlap the domain wall 8. The arrangement pitch of the sawtooth-shaped teeth at the edge of the ferromagnetic layer 12 is, for example, about 4 pm. The ferromagnetic layer 12 having such a planar shape can be formed by, for example, ion milling.

FIGS. 2(a) and 2(b) are schematic plan views showing pairs of Bloch lines within a domain wall.

FIG. 2(a) shows the blow and hole pair in one domain wall portion 8a shown in FIG. 1(a) above, and FIG.
b) shows the Bloch line pair in the other domain wall portion 8b. As shown in FIG. In the part of the line pair, the part between the two Bloch lines 1O faces to the left. As shown in FIG. 2(b), the domain wall magnetization in the domain wall portion 8b is directed to the left in the portion other than the Bloch line pair, and in the Bloch line pair portion, the portion between the two Bloch lines 10 is oriented to the left. On the contrary, it is facing to the right.

FIGS. 3 and 4 are diagrams for explaining the magnetic properties within the domain wall in this example.

(&) in Figure 3 is the domain wall portion 8 in Figure 1 (a) above.
It shows the partial plane shape along the direction a, and (b) in Fig. 3 shows the partial plane shape along the direction a.
is a graph showing the in-plane magnetic field component along the direction of the domain wall with the rightward direction being positive at the position within the domain wall corresponding to FIG. 3(k), and (C) of FIG. It is a graph showing the distribution of force required for movement.

As shown in FIG. 3(b), the ferromagnetic layer 12 is magnetized in the X direction, and the planar shape of the edge of the ferromagnetic layer is a directional sawtooth shape on the domain wall portion 8a. The in-plane magnetic field component H2 in the X direction generated based on this has a sawtooth distribution with periodicity corresponding to the uneven shape of the edge portion of the ferromagnetic layer 12. L2 As shown in FIG. 2(a), in the magnetic 1V portion 8a, the direction of domain wall magnetization between the two Bloch lines 10 of the Bloch line pair is leftward, so the negative portion of H9 (FIG. 3) In (b) 18
The Bloch line pair is stably located at the point (indicated by ), which becomes a potential well.

In this embodiment, when a pulsed magnetic field is applied downward in the thickness direction of the magnetic thin film 4, the domain wall portion 8a is caused by the gyroscopic effect.
The magnetization within the domain wall rotates clockwise in FIG. The magnitude of the driving force for the Bloch line pair movement due to this gyroscopic effect is (4π/γ) M V wal l . Here, γ is the gyro constant and M is the domain wall 8
is the magnitude of saturation magnetization, and vwa1□ is the domain wall movement speed. In the part where the Bloch line exists, the domain wall movement speed is vwall;αγn11He, so the magnitude of the above driving force is 4πfiMa*He, where A is the parameter within the domain wall, and α is Gilbert's damping constant. , He acts on the domain wall z
is the effective magnetic field in the direction (including the pulsed magnetic field Hp and the change in the demagnetizing field due to domain wall movement).'' On the other hand, based on the presence of the above-mentioned in-plane magnetic field component H2,
Rotation of magnetization within the domain wall due to the above-mentioned gyro effect is suppressed. The magnitude of this suppressing force is 2πAMeH sentence.

Therefore, the driving force Fd that moves the Bloch line to the right in the domain wall portion 8a is Fd=4πf1Mct*HHe-2trn*H.

= 2 πX Ma (2He Hx / Q)
Since α is smaller than l, Hx is extremely effective in controlling Bloch line movement. That is, at a position where Hx is positive, extra force is required to move the Bloch line pair compared to when there is no in-plane magnetic field component. Assuming that this force is F', F' has a distribution as shown in FIG. 3(C).

In this figure, the rightward force is considered positive, and the blow 2
To move the Bloch line pair to the right, a driving force as shown by the solid line is required, and to move the Bloch line pair to the left, a driving force of the opposite polarity as shown by the dotted line is required. is necessary.

FIG. 4(a) is the domain wall portion 8 in FIG. 1(a) above.
It shows the partial plane shape along b, and (b) in Fig. 4
is a graph showing the in-plane magnetic field component along the direction of the domain wall at the position within the domain wall corresponding to FIG. 4(a), with the rightward direction being positive; FIG. It is a graph showing the distribution of force required for anti-movement. These are the same figures as FIGS. 3(&) to (C) above.

As shown in FIG. 2(b) above, in the domain wall portion 8b, the direction of domain wall magnetization between the two Bloch lines 10 of the Bloch line pair is rightward, so the positive portion of H (see FIG. The Bloch line pair is stably located at a point (indicated by 20 in (b)), which becomes a potential well.

When a pulsed magnetic field is applied downward in the thickness direction of the magnetic thin M4, the magnetization within the domain wall in the domain wall portion 8b rotates clockwise in FIG. 2(b) in the same manner as explained with reference to FIG. As a result, the Bloch line pair is moved to the left along the domain wall portion 8b (in addition, at this time, the Bloch line pair is moved leftward along the domain wall portion 8b).
is also generally moved upward in the y direction).

In the domain wall portion 8b, at a position where Hx is negative, extra force is required to move the Bloch line pair compared to when there is no in-plane magnetic field component. If this force is F', then dF' has a distribution as shown in FIG. 4(C). In this figure, the leftward force is positive, and in order to move the Bloch line pair leftward, a driving force as shown in the X-ray is required, and in order to move the Bloch line pair rightward, a leftward force is required. A driving force as shown by the dotted line with the opposite polarity is required.

FIG. 5 is a diagram showing the above-mentioned pulsed magnetic field and the driving force for moving the Bloch line pair generated with the application of the pulsed magnetic field.

FIG. 5(a) shows a waveform diagram of the pulsed magnetic field HP, which is a substantially rectangular pulsed magnetic field whose rise time and fall time are equal (for example, rise time t = 50n).
sec, peak time t = 1r
Po
0 n s e c , s'1 time t f = 50
The fact that He changes with time due to the application of this pulsed magnetic field, which is 1; is generated, and a negative force (indicated by 24 in FIG. 5(b)) is generated at the time of falling.The driving force 22 drives the Bloch line pair rightward in the domain wall portion 8a, and 8b drives the Bloch line pair leftward.On the other hand, the driving force 24 drives the Bloch line pair leftward in the domain wall portion 8a, and drives the Bloch line pair rightward in the domain wall portion 8b.

Therefore, as the driving force 22, FIG. 3(C) and FIG. 4(
By determining the waveform of the pulsed magnetic field so that a driving force having a larger peak value than the force shown by the solid line in C) is generated, the magnetic domain wall portion 8a increases as the pulsed magnetic field rises.
Then, the Bloch line pair moves to the right over the potential wall to the adjacent potential well, and at the domain wall portion 8b, the Bloch line pair moves to the left over the potential wall to the adjacent potential well.

Then, as the pulse magnetic field falls, the Bloch line pair receives a leftward force in the 8i wall portion 8a due to the driving force 24 (11-)), and the Bloch line pair receives a rightward force in the fii wall portion 8b, but in this case, it moves. Since the potential wall in the desired direction exists over a long distance, the driving force 24 disappears before the Bloch line pair crosses the potential wall, and eventually the Bloch line pair returns to the adjacent original potential. It cannot move into the well, thus resulting in the Bloch line pair being moved clockwise by one potential well.

In the above embodiment, the periodic uneven shape of the edge of the magnetic layer formed on the surface of the magnetic thin film has a sawtooth shape, but in the present invention, the uneven shape has a directionality. Any other suitable shape may be used as long as it has a shape.

Furthermore, in one aspect of the present invention, the magnetic layer may be formed so as to correspond to a region other than the stripe magnetic domain (i+Tf7).

[Effect of the invention 1] According to the present invention as described above, the Bloch line can be reliably transferred in a specific direction by applying a Qi pure rectangular pulse magnetic field. Since the time is short, the transfer speed can be improved and the access time can be shortened, and the power consumption can also be reduced, thus making it possible to realize a Bloch line memory that is stable, high-speed, and operates well with a simple configuration.

[Brief explanation of drawings]

FIG. 1(a) is a partial plan view of the Bloch line memory of the present invention, and FIG. 1(b) is a sectional view thereof taken along line B--B. FIGS. 2(a) and 2(b) are schematic plan views showing pairs of Bloch lines within a domain wall. FIGS. 3 and 4 are diagrams for explaining magnetic properties within a domain wall. FIG. 5 is a diagram showing a pulsed magnetic field and a driving force for moving a pair of Bloch lines generated due to the application of the pulsed magnetic field. FIG. 6 is a schematic perspective view of the magnetic structure constituting the Bloch line memory. FIG. 7 is a partial plan view of the Bloch line memory. FIG. 8 is a diagram showing the waveform of the pulsed magnetic field. 2: plate, 4: magnetic thin film, 6: magnetic domain, 8: domain wall, lO: Bloch line, 12 two ferromagnetic layers. Agent Patent Attorney Jo Taira Yamashita Figure 3 Figure 4 1?

Claims (2)

[Claims] (1) In a Bloch line memory that records information using Bloch lines within a domain wall formed around a magnetic domain in a magnetic thin film, a magnetic layer is partially formed on the magnetic thin film, and the magnetic A Bloch line memory characterized in that the planar shape of at least a part of the edge of the body layer has a periodic uneven shape that crosses the domain wall and has directionality along the domain wall. (2) The Bloch line memory according to claim 1, wherein the magnetic thin film is a magnetic garnet thin film.