JPH03154283A - Magnetic memory element and its manufacturing method - Google Patents

Abstract

PURPOSE:To increase the bit density of a storage element by forming a vertical magnetization pattern to a second magnetic thin film pattern formed on the first magnetic thin film of a single crystal which holds a Bloch line using a magnetic flux generated by a magnetic head. CONSTITUTION:A stripe domain 2 exists in the first magnetic thin film 1 of the single crystal. The magnetization is perpendicular to the plane of the figure and in a downward direction inside of the stripe domain 2, and is perpendicular to the plane in an upward direction on the outside. In a roughly parallel direction to the stripe domain 2 of the magnetic thin film 1 and its magnetic wall 3, the direction 9 of the magnetization of the magnetic thin film 1 is reversed in a prescribed cycle. On the other hand, the direction 9 of the magnetization of the magnetic thin film 1 does not change when in a direction roughly orthogonal to the striped domain 2 and its magnetic wall 3. Such magnetic pattern is used for vertical magnetic recording, and can be formed by the magnetic flux generated from the gap 11 of a ring-shaped magnetic head 10.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a Bloch line memory element using a Bloch line memory existing in the domain wall of a stripe domain of a single crystal magnetic thin film having an axis of easy magnetization perpendicular to the film surface. In relation to
In particular, it relates to the transfer pattern of Bloch line pairs, which are information carriers.

[Conventional technology]

In a single-crystal magnetic thin film for magnetic bubbles (for example, a magnetic garnet film), the boundaries of magnetic domains (regions perpendicular to the thin film surface and magnetized upward or downward) are called domain walls.

In most regions of this domain wall, the magnetization is oriented in a direction parallel to the domain wall surface, forming a Bloch domain wall. However, within this Bloch domain wall, there are parts where the direction of magnetization is reversed. In this magnetization reversal portion, the direction of magnetization is perpendicular to the domain wall surface, forming a Neel domain wall.

This part of the Neel domain wall in the domain wall is called the Bloch line.

As shown in FIG. 3(a), the Bloch line is a positive Bloch line 5 that rotates with magnetization pointing upward in the figure when the direction of magnetization in the domain wall 3 changes from rightward direction 3a to leftward direction 3b.
a, and a negative Bloch line 5b that rotates with its magnetization directed downward in the figure, as shown in FIG. 3(b).

Furthermore, when two Bloch lines are close to each other and the polarities of the Bloch lines 5 are both positive as shown in FIG. 3(c), the two Bloch lines 5-1°5-2
When , the Bloch lines 5-1, 5-2 disappear, forming an unstable pair. This also applies to the case where the polarities of the two Bloch lines 5-1, 5-2 are both negative Bloch lines 5b. Therefore, if the polarities of the two Bloch lines 5-1 and 5-2 are a combination of positive and negative as shown in FIG. .5-2, it twists once, so even if they are close, the Bloch line is 5-1.5-2.
does not disappear and forms a stable pair.

A Bloch line memory device uses such Bloch line pairs as information carriers.

Regarding the principle of Bloch line memory elements, see, for example, IE Transactions on Magnetics, MNG 19, (1983).
Pages 1838 to 1840 (Engineering EEE, Trans
, Magnetics, MAG-19, (19
83) pp. 1838-1840).

To move such Bloch line pairs, a bias magnetic field pulse (amplitude 3 to 300) is applied perpendicularly to the single crystal magnetic thin film.
e) may be applied. The Bloch line pair moves along the domain wall due to the rotation of magnetization and movement of the domain wall caused by the bias magnetic field pulse. Details of this are described in the above-mentioned document.

Although the Bloch line pair can be moved using bias magnetic field pulses, it is difficult to make the distance moved by one pulse the same every time. In particular, when a row of Bloch line pairs corresponding to a data pattern is lined up, the moving distance of the Bloch line pairs is different depending on a part where many Bloch line pairs exist in close proximity and a part where they exist in isolation. . Therefore, for Bloch line pair transfer, a transfer pattern similar to bubble transfer in a bubble memory or a bit fixing pattern is required. IE Transaction on as an example of a transfer pattern
Magnetics, M.G.22 (1983
), pp. 784-789 (IEEE, Tran
s, Magnetics, MAG-22 (19
83), pp. 784-789), there is a method in which a striped conductor pattern is formed on a single crystal magnetic thin film and a current is applied to this. Bloch line bit fixation is achieved by applying direct current to periodically arranged conductor patterns. Furthermore, as described in Japanese Patent Application Laid-Open No. 59-98384, there is also a method in which a striped magnetic thin film is formed on a single crystal magnetic thin film in a direction perpendicular to the striped magnetic domains. This is done by setting the coercive force (Hc) of the striped magnetic thin film to an appropriate value to set the Bloch line at a predetermined position.

In either bit fixing method, the repetition period of the pattern is a bit length of 1 bit.

Further, a domain wall including Bloch line pairs exists at the boundary of striped magnetic domains. Therefore, in the Bloch line memory element, it is necessary to fix the stripe magnetic domains at predetermined positions. As a method for fixing striped magnetic domains, as described in IEE Transactions on Magnetics, M.N.G. 22, (1986), pages 784 to 789, striped magnetic domains are fixed by grooves in a single-crystal magnetic thin film. A method of forming and fixing a pattern is used. As for the depth of the groove pattern, it is effective to remove all the single crystal magnetic thin film at the groove and use a 100% group. Using the leakage magnetic field generated around this groove,
Striped magnetic domains can be fixed around this groove.

[Problem to be solved by the invention]

Among the above conventional techniques, those using conductor patterns,
The bit cannot be fixed if there is no externally supplied current. Therefore, it has the disadvantage that it cannot be used as a nonvolatile memory because it cannot store information when the power is turned off. Furthermore, in any of the above conventional techniques, the length of one bit is determined by the repetition period of the conductor pattern or stripes of the magnetic thin film. The current phosphorography technology has a limit of forming a pattern with a width of 0.6 μm at a repetition period of 1.2 μm. Furthermore, it is extremely difficult to uniformly create a pattern with such dimensions without defects. For example, when using a 0°4 μm bubble material, the width of the striped magnetic domain is approximately 0.4 μm, so the bit width can be set to 0.4 μm, and therefore the bit density of Bloch line memory is also approximately 200 Mb/aJ. be able to. However, pattern formation is an important issue in realizing such high-density devices. Moreover, even at this high density, it is extremely difficult to produce devices with few defects.

On the other hand, in the method proposed in Japanese Patent Application No. 63-41988, a magnetic thin film is formed in a --like manner on a single crystal magnetic thin film including Bloch lines, and within this magnetic thin film, the single crystal magnetic thin film is A magnetic domain pattern is formed that is almost perpendicular to the stripe domain of the magnetic field.

The Bloch line pair is fixed using the leakage magnetic field generated from this magnetic domain pattern.

FIG. 4 shows an example in which a perpendicular magnetization film is used as the magnetic thin film for bit fixing. In this figure, 2-1 to 3 are striped domains, 3-1 to 3 are domain walls, 4-1 to 7 are Bloch line pairs, 6 is an insulator spacer, 7 is a perpendicular magnetization film,
9 is the magnetization direction of the perpendicularly magnetized film.

The problem with using this perpendicular magnetization film is that this film is formed on the above-mentioned stripe fixing groove.

As shown in Figure 5, the width is about the same as the stripe magnetic domain width (0,5
It is necessary to form the perpendicular magnetization film 7 after filling the groove 15 (~5 μm) with a resin 16 or the like and sufficiently flattening it. When this flattening is performed using a resin, it is necessary to apply the resin in multiple times.

It is also necessary to reduce the thickness of the film in areas other than the grooves by etching it from above after coating.

There are also methods for forming deep grooves for fixing stripes, such as ion implantation and phosphoric acid etching, and ion milling, but each method has its advantages in terms of process time and processing accuracy.

An object of the present invention is to provide a bit fixing pattern and a stripe fixing pattern that can reduce the bit length of a Bloch line memory element without being limited by phosphorography.

[Means to solve the problem]

The above object is to form a second magnetic thin film pattern on a first single crystal magnetic thin film that maintains Bloch lines, and to form a second magnetic thin film pattern in the second magnetic thin film in a direction substantially perpendicular to the stripe domain of the first magnetic thin film. This is achieved by forming a magnetic domain pattern. The magnetization of the second magnetic thin film is perpendicular to the plane of the second thin film.

This magnetic domain pattern can be formed using a ring type head or a single magnetic pole type head used in magnetic recording. In the magnetic domain pattern, by making the width of the magnetic domain with magnetization in the same direction as the striped domain larger than the width of the magnetic domain with magnetization in the opposite direction, it is possible to generate a magnetic field that attracts the entire striped domain, Stripe fixation can be achieved.

[Effect]

A second magnetic thin film pattern is formed on a single-crystal first magnetic thin film including striped domains that maintain Bloch lines in its domain walls or on an insulating layer formed on the first magnetic thin film. The second magnetic thin film pattern is a thin film that is easily magnetized in the direction perpendicular to the thin film surface. In addition, the coercive force Hc is sufficiently larger than the saturation magnetic flux thickness 4πMs of the first magnetic thin film.
It is necessary to have That is, it is necessary to prevent the magnetization of the second magnetic thin film from changing due to the magnetic field generated by the first magnetic thin film. within the second magnetic thin film.

A magnetic head or the like is used to form a striped magnetic domain pattern in a direction substantially perpendicular to the substantially parallel striped domains formed in the first magnetic thin film. That is, by making the local magnetic field generated by a magnetic head or the like larger than the coercive force Ha of the second magnetic thin film, the magnetic domains of the second magnetic thin film are made into the above-described striped shape. Each magnetic domain has magnetization oriented in the perpendicular direction. Due to the magnetization of the second magnetic thin film, a magnetic field whose direction changes periodically along the direction of the domain wall is applied to the domain wall of the stripe domain in the first magnetic thin film. This magnetic field forms stably existing positions of Bloch line pairs.

Transfer of Bloch line pairs is performed by applying a bias magnetic field pulse having a sufficiently stronger driving force than this magnetic field. Since the magnetization pattern of the second magnetic thin film is formed using a magnetic head, there is no need for microfabrication technology to process the second magnetic thin film into a width equal to the bit length, and the gap width of the magnetic head is made sufficiently small. By localizing the magnetic field, the width of the striped magnetic domains generated in the second magnetic thin film pattern can be made sufficiently small. Therefore, a Bloch line memory element with a short bit length can be realized without being limited by microfabrication technology.

Furthermore, by making the width of the magnetic domain having magnetization in the same direction as the stripe domain in the second magnetic thin film pattern larger than the width of the magnetic domain having the opposite magnetization direction,
The total sum of the magnetic field generated from the entire second magnetic thin film can be set in a direction that attracts the striped domains. As a result, stripe fixation can be achieved.

〔Example〕

Example 1 A first example of the present invention is shown in FIG. FIG. 1(a) is a plan view of the Bloch line memory element of this example,
FIG. 1(b) is a sectional view taken along the line AA'.

The stripe domains 2 exist in the single-crystal first magnetic thin film 1. Inside the striped domain 2, the magnetization is perpendicular to the paper plane and downward, and outside it is perpendicular to the paper plane and upward.

In the cross-sectional view of FIG. 1(a), the directions are downward and upward, respectively. The boundary between the striped domains 2 is a domain wall 3, which is a Bloch-type domain wall in the magnetic thin film 1 used here.

If there is no Bloch line within the domain wall 3, the domain wall 3
The magnetization within −1 to 3 is rightward as shown in the cross-sectional view. This is determined by the in-plane magnetic field applied from the outside in eight directions. The magnitude of this in-plane magnetic field 8 needs to be on the order of 2 to 100 e. A magnetic thin film pattern 7 is arranged on the magnetic thin film 1 or on the insulating film 6 sandwiched therebetween. In this embodiment, this magnetic thin film 7 is magnetized in a direction perpendicular to the plane. Processing is performed such that the direction of magnetization 9 is directed at each location in the direction shown in the plan view and cross-sectional view of FIG. 1, respectively. That is, in a direction substantially parallel to the direction of the striped domain 2 of the magnetic thin film 1 and its domain wall 3, the direction 9 of magnetization of the magnetic thin film 2 is reversed at a predetermined period. On the other hand, the direction 9 of magnetization of the magnetic thin film 2 does not change in a direction substantially perpendicular to the direction of the striped domain 2 and its domain wall 3.

Such a magnetization pattern is used in perpendicular magnetic recording, and can be formed by a magnetic field generated from the gap 11 of the ring-shaped magnetic head 10 shown in FIG.

Further, it can be generated by a single magnetic pole type head for perpendicular magnetic recording shown in FIG. magnetic head 10 or 11
is placed at a predetermined position on the magnetic thin film 7, and a current pulse is applied to the coil 12 of the magnetic head 10 or 13 so that an upward magnetic field is applied to the magnetic thin film 7, thereby creating an upwardly magnetized region on the magnetic thin film 7. Form. Next, the position of the magnetic head 10 or 13 is moved to the left or right by a predetermined distance, and a current pulse of opposite polarity to the above is applied to the coil 12 of the magnetic head 10 or 13, thereby removing the downwardly magnetized region. It is formed on the magnetic thin film 7. By repeating this operation, a magnetization pattern as shown in FIG. 1 can be formed in the second magnetic thin film. The gap width of the magnetic head 10 or 13 can be reduced to 0 if manufactured using a thin film process.
．． It can be made as small as 1 to 0.2 μm. Furthermore, writing of the magnetization pattern is a one-time process, and there is no need to move the magnetic thin film 7 at high speed as in normal magnetic recording operations. Therefore, the distance between the head and the magnetic image [7] can be made extremely small. Therefore, magnetic image 1
1! By setting the material properties and film thickness of J 7 to appropriate values, it is possible to set the repetition period of the magnetization pattern of the magnetic thin film 7 to 0.2 to 064 μm.

The composite magnetic field of the magnetic field generated by the magnetic thin film 7 formed by the method described above and the externally applied in-plane magnetic field 8 is as shown by the arrow in FIG. 8 in the single crystal magnetic thin film 1.

If this strength is expressed as a positive value for the rightward direction and a negative value for the leftward direction, it will be as shown in FIG. That is, in the central part of the region 9-1 where the magnetic thin film 7 is magnetized upward and in the part of the magnetic thin film 1 below the region 9-2 where the magnetic thin film 7 is magnetized downward, the magnetic field 14
The direction of is to the left. On the other hand, in the portion of the magnetic thin film 1 below the central portion of the region 9-2 that is magnetized to the left, the direction of the magnetic field 14 is to the right.

The magnetization within the domain wall 3 between Bloch lines 5-1 and 5-2 exists when the Bloch line pair 5-1.5-2 shown in FIG. The region 12 where the magnetic field is directed to the left exists in the portion 4-1°4-2 of the magnetic thin film 1 where the composite in-plane magnetic field is directed to the left. Therefore, the Bloch line pair 5-1.5-2 is equal to this 4-1.4
-2. In FIG. 1, the stable positions of Bloch line pairs are 4-1 to 4-8.

As a result of the above, it becomes possible to hold or fix the Bloch line pair 5-1, 5-2 at a predetermined position by the magnetic field generated by the perpendicular magnetization pattern of the magnetic thin film pattern 7.

Bit fixing using this method does not significantly differ in the magnetic field applied to the magnetic thin film 1 from fixing using a conventional striped conductor pattern or striped magnetization pattern, so Bloch line transfer can be achieved by applying magnetic field pulses as in the conventional method. It is possible to do so.

On the other hand, regarding the fixation of the drive magnetic domain, as mentioned above,
In addition, as shown in FIG. 1, by increasing the number of downward magnetization regions of the magnetic thin film pattern 7 compared to the upward magnetization direction, stripe magnetic domains can be separated from the magnetic thin film pattern 7.
The sum of the components of the magnetic field applied in the direction perpendicular to the plane is downward. As a result, the stripe magnetic domain 3 becomes the magnetic thin film pattern 7.
is sucked under. As a result, stripe magnetic domain fixation can be realized.

As described above, if the method of this embodiment is used, the bit period is 0.
．． It becomes possible to realize a Bloch line memory element of 2 to 0.4 μm. By setting the bubble diameter (strip domain width) of the bubble material used to 0°4 μm,
Bloch line memory devices of 800 Mb to 1.2 Gb/cd can be realized.

[Embodiment 2] A second embodiment of the present invention will be described using FIG. 2. The second magnetic thin film patterns 7-1 to 7-3 for bit fixing and stripe fixing in this embodiment are the same as those in the first embodiment. The difference is that the second magnetic thin film patterns 7-1 to 7-3
This is the magnetic domain structure of

In order to hold the striped magnetic domains at a predetermined position as described above, it is necessary to apply a magnetic field perpendicular to the surface of the single crystal magnetic film 1 and in the same direction as the magnetization of the striped magnetic domains to the portion where the striped magnetic domains are desired to be fixed. The bit fixing pattern shown in FIG. 1 has a problem in that the position of the tip of the striped magnetic domain moves depending on the magnitude of the magnetic field (bias magnetic field) applied to the entire element in a direction perpendicular to the single crystal magnetic film 1.

Therefore, in this embodiment, as shown in FIG. 2, the magnetic domains 16 at the ends of the magnetic thin film pattern are oriented upward, thereby increasing the variation depending on the location of the perpendicular magnetic field applied near the tips of the striped magnetic domains. As a result, it was possible to solve the problem that the position of the stripe magnetic domain tip was moved by the bias magnetic field.

In this method, the width of the downward magnetic domain 17 at the end of the second magnetic thin film pattern is 0.5 to 3 of the stripe magnetic domain width.
The width of the upward magnetic domain 16 is 1 to 5 times the width of the stripe magnetic domain.
It's double.

〔Effect of the invention〕

According to the present invention, a pair of Bloch lines is fixed by forming a perpendicular magnetization pattern using a magnetic head or the like on a second magnetic thin film pattern formed on a first single-crystal magnetic thin film that holds Bloch lines. Since it is possible to form patterns for transfer and transfer, it solves the problem of limitations on minimum processing dimensions and many defects in fixing Bloch line pairs using conventional glue lithography and forming thin film patterns of magnetic materials and conductors for transfer. However, since the period of one bit can be reduced from the conventional limit value of 1.2 .mu.m to 0.2 to 0.4 .mu.m, there is an effect that the bit density of the Bloch line memory element can be increased by 3 to 6 times.

[Brief explanation of the drawing]

1 and 2 are diagrams showing the planar shape and cross-sectional shape of a memory element according to an embodiment of the present invention, FIG. 3 is a diagram showing the magnetization of a domain wall including Bloch lines and Bloch line pairs, and FIG. 4 is a diagram showing vertical A plan view and a sectional view showing a conventional method of bit fixing using a magnetized film, FIG.
FIG. 7 is a front view showing a magnetic head used in an embodiment of the present invention, and FIG. 8 is a diagram showing a composite magnetic field of a magnetic field generated by a second magnetic thin film and an external magnetic field in a second embodiment of the present invention. , FIG. 9 is a diagram showing the distribution of the composite magnetic field in the first embodiment. Explanation of symbols 1...Single crystal magnetic thin film, 2...Stripe domain, 3...Domain wall, 4...Stable position of Bloch line,
Death...Bloch line, 6...Insulating layer, 7...Second
magnetic thin film, 8... external magnetic field, 9... magnetization of second magnetic thin film, 10... ring type magnetic head, 11...
Gap of magnetic head, 12... Coil of magnetic head, 13... Single pole type magnetic head, 14... Nonmagnetic substrate, 15... Groove pattern of single crystal magnetic film, 16.
...Resin'1fJl Figure (b) Z Figure (b) Atsushi ■

Claims (1)

[Claims] 1. Bloch lines existing in the domain walls of striped domains of a single crystal first magnetic thin film having an easy axis of magnetization perpendicular to the film surface are used as information storage means, and the first magnetic A pattern consisting of a second magnetic thin film formed on a thin film or an insulating layer formed on the first magnetic thin film, and the second magnetic thin film pattern has a magnetic domain magnetized perpendicular to the film surface. A magnetic memory element characterized in that stripe domains are identified and Bloch lines are fixed by leakage magnetic fields generated from the magnetic domains. 2. The magnetic memory element according to claim 1, wherein the second magnetic thin film pattern is magnetized in a direction perpendicular to the film surface. 3. The magnetic memory element according to claim 1, wherein the width of the second magnetic thin film pattern is 1 of the width of the stripe domain.
A magnetic memory element characterized in that the magnetic memory element is three times as large. 4. A method of manufacturing a magnetic memory element according to claim 1, wherein a magnetic field generated by a magnetic head is used to form a magnetic domain pattern of the second magnetic thin film. 5. The method for manufacturing a magnetic memory element according to claim 4,
A method of manufacturing a magnetic memory element, wherein the magnetic head is a ring-shaped head. 6. The method for manufacturing a magnetic memory element according to claim 4,
A method of manufacturing a magnetic memory element, wherein the magnetic head is a single-pole head. 7. In a magnetic memory element that uses as an information carrier a Bloch line existing in a domain wall of a stripe domain of a first magnetic thin film having an axis of easy magnetization perpendicular to the film surface, provided in contact with the first magnetic thin film pattern. . A magnetic memory element further comprising a second magnetic thin film in which a magnetic domain pattern is formed in a direction substantially perpendicular to the longitudinal direction of the striped domains. 8. The magnetic memory element according to claim 1, wherein the second magnetic thin film is provided with an insulating layer interposed therebetween. 9. In a magnetic memory element that uses as an information carrier Bloch lines existing in the magnetic domain walls of striped domains in a first magnetic thin film having an axis of easy magnetization perpendicular to the film surface, provided in contact with the first magnetic thin film. A magnetic memory element comprising a magnetic domain pattern of the Bloch line fixing and stripe magnetic domains in the second magnetic thin film pattern.