JPH05189956A - Bloch line memory element - Google Patents

Abstract

PURPOSE:To widen a margin for reading out and erasing without generating a malfunction and to provide a solid-state memory having high versatility by cutting magnetic domains by using two pieces of such parallel conductors with which a specific magnetic field distribution is obtainable. CONSTITUTION:Two pieces of the parallel conductors 10 which are formed via a spacer 14 on a ferromagnetic material 13 are used. The magnetic fields generated by the parallel conductors 10 when the currents equal in amplitude and reverse from each other are impressed to the respective parallel conductors have the characteristic that the place where the vertical components thereof on the surface of the ferromagnetic material film attain the max. value and the place where the intra-surface components of the magnetic fields on the ferromagnetic material film surface are zero at least coincide with each other. The stripe magnetic domains having a Bloch line are not cut and the generation of such a malfunction that the magnetic domains without having the Bloch line are cut is obviated if the operation to cut the magnetic domains is executed by using such parallel conductors 10. The margin for reading out or erasing is thus expanded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid magnetic memory,
In particular, it relates to a Bloch line memory element suitable for realizing a large capacity file memory.

[0002]

2. Description of the Related Art Regarding Bloch line memory devices,
Japanese Patent Laid-Open No. 59-101092 describes a basic memory configuration. In this Bloch line memory element, the presence / absence of Bloch line pairs existing in the domain wall of the stripe magnetic domain arranged in the ferromagnetic material having the easy axis as the direction perpendicular to the film surface is used as information "1", "0". It is stored in correspondence with ". Since the Bloch line memory element cannot directly detect the Bloch line pair, which is an information carrier, the Bloch line is converted into a detectable bubble magnetic domain to read information. Therefore, a method of converting the presence or absence of Bloch lines into the presence or absence of bubble magnetic domains is important.

The method for converting the presence or absence of Bloch lines into the presence or absence of bubble magnetic domains is described in detail in the above-mentioned publication. The method will be described with reference to FIG. Figure 3
(A) shows a stripe magnetic domain 1 having a Bloch line 3 at the end and a stripe magnetic domain 1'having no Bloch line. The two parallel conductors 10 arranged orthogonal to each stripe magnetic domain are magnetic domain cutting conductors.
Magnetization 15-1 in the domain wall in the domain wall 2 around the stripe domain,
Focusing on 15-2, in the stripe domain 1 having the Bloch line 3 at the end, the directions of the domain wall magnetizations 15-1 on both sides thereof are parallel, and in the stripe domain 1 ′ having no Bloch line, the domain wall magnetizations on both sides thereof. The direction of 15-2 is anti-parallel. Therefore, when the domain walls on both sides of the striped magnetic domain are brought close to each other, the exchange energy acting between the two domain walls of the striped magnetic domain having the Bloch line 3 at the end is reduced, and in the striped domain 1 ′ having no Bloch line. Exchange energy increases. Therefore, when current Ig having a predetermined amplitude is applied to the magnetic domain cutting conductors 10 in opposite directions to generate a local magnetic field Hz, and the magnetic domain walls on both sides of the stripe magnetic domain are brought closer to each other, the result is as shown in FIG. As shown, the striped magnetic domain having the Bloch line 3 at the end is cut and a new bubble magnetic domain 16 is formed, but the striped magnetic domain having no Bloch line is not cut.
In this way, the presence or absence of Bloch lines is converted into the presence or absence of bubble magnetic domains.

In this conversion method, the read margin is greatly affected by the distribution of the magnetic field applied by the magnetic domain cutting conductor 10. A method for optimizing the distribution of the applied magnetic field and expanding the read margin is disclosed in JP-A-63-308781. As shown in Fig. 4, the magnetic domain cutting conductor has a magnetic field distribution applied so that the absolute value of the vertical magnetic field component or the horizontal magnetic field component has one maximum peak, and the position where the maximum peak is taken is plotted. Three
In the left diagram of (b), it was arranged near the conductor on the side closer to the stripe magnetic domain 1.

[0005]

When the above conventional technique is used, it is possible to increase the read margin.
In order to obtain a desired magnetic field distribution, it is necessary to apply currents having different amplitudes to the two parallel conductors, and there is a problem that a dedicated circuit must be prepared for that purpose. Also,
In order to obtain the desired magnetic field distribution, it was necessary to make the width and thickness of each of the two parallel conductors, or the spacing from the surface of the magnetic garnet film (ferromagnetic material film) different, which made the device manufacturing process complicated. There was a problem of becoming. Further, no quantitative disclosure has been made regarding the conductor shape for obtaining a desired magnetic field distribution.

An object of the present invention is to disclose a magnetic field distribution capable of expanding a read margin with a conductor having a shape which does not use a dedicated circuit and has a simple manufacturing process, and a conductor which generates a magnetic field having such a distribution. To provide quantitatively the shape of.

In particular, in an element using a material having a magnetic domain width of 1 μm or less that can realize a storage density of 256 Mb / cm ² or more, it is difficult to form the gap size between two parallel conductors by the existing photolithography method. It is to quantitatively provide a conductor shape that does not have the submicron size.

[0008]

An object of the present invention is to provide a Bloch line present in domain walls of stripe domains arranged in parallel in a ferromagnetic film having an easy axis of magnetization in a direction perpendicular to the film surface. In a Bloch line memory element using a pair as an information carrier, two parallel conductors formed on the ferromagnetic material via a spacer are used, and the parallel conductors have equal amplitudes to each other and generate a reverse current. At least the place where the vertical component on the surface of the ferromagnetic film of the magnetic field generated when applied has a maximum value and the place where the in-plane component of the magnetic field on the surface of the ferromagnetic film becomes 0 are at least. Have matching features,
This is achieved by performing a magnetic domain cutting operation using the parallel conductor. According to our calculation, the conductor condition for realizing this is that the width of two parallel conductors is a, the thickness is b,
When the gap size is g and the spacer thickness is s,
It was clarified that this was achieved by determining each value so as to satisfy the following two equations.

G ² + (g + 2a) ² > 8s (s + b) g ² (g + 2a) ² > 8s (s + b) {g ² + (g + 2a) ² +6 (s + b) ² + 2b ² } Especially 256 Mb / cm ² or more This can be achieved by satisfying the above two expressions so that the gap dimension g between two parallel conductors does not become a submicron dimension for an element using a material having a magnetic domain width of 1 μm or less that can realize a memory density.

[0010]

[Function] The magnetic field generated on the surface of the ferromagnetic film is equal to each other of the two parallel conductors formed on the ferromagnetic film via the spacers, and the magnetic field generated when the opposite currents are applied. At least the location where the vertical component takes the maximum value and the location where the in-plane component of the magnetic field on the surface of the ferromagnetic film becomes 0, that is, the width of the two parallel conductors 10 in FIG. Where a is the thickness, b is the gap dimension, g is the gap dimension, and s is the thickness of the spacer 14, the values are determined so as to satisfy the following two equations. Becomes as shown in FIG.

G ² + (g + 2a) ² > 8s (s + b) g ² (g + 2a) ² > 8s (s + b) {g ² + (g + 2a) ² +6 (s + b) ² + 2b ² } The stripe magnetic domain has a maximum vertical magnetic field component. Is cut, that is, at the center of the gap (x = 0 point). If there is an in-plane magnetic field component at the point where the stripe magnetic domain is cut, a horizontal Bloch line is generated by the in-plane magnetic field, which causes a malfunction. That is, in FIG. 3, a situation may occur in which the striped magnetic domain 1 having the Bloch line 3 is not cut and the striped magnetic domain 1'having no Bloch line is cut. Therefore, the read margin is narrowed. In the present invention, as shown in FIG. 2, the in-plane magnetic field component becomes zero at the point where the vertical magnetic field component becomes maximum. Therefore, such a malfunction does not occur and the read margin can be expanded.

Further, in particular, in an element using a material having a magnetic domain width of 1 μm or less capable of realizing a storage density of 256 Mb / cm ² or more, when the thickness s of the spacer is increased, the gap dimension g between the two parallel conductors becomes sub- The above two equations can be satisfied so that micron size is not achieved.

In the present invention, the width and thickness of each of the two parallel conductors are the same, the spacing with the magnetic garnet film is the same, and the amplitude of the applied current is also the same, so that the conductor manufacturing process is simple and a dedicated circuit is also available. do not need.

[0014]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 (a) is a diagram showing a functional portion of a Bloch line memory, and FIG. 1 (b) is a sectional view taken along the line AA 'in FIG. 1 (a). Stripe domain 1 has a thickness of 0.
It was present in a GdGa-based magnetic garnet film (ferromagnetic material film) 13 having a thickness of about 1 μm grown on a 4 mm gadolinium gallium garnet substrate 12 and fixed around the stripe magnetic domain fixing pattern 5. In this material, the stripe magnetic domain width is about 1 μm, and the stripe magnetic domain is 256 Mb / cm ²
The memory density of can be realized. The guide pattern 6 plays the role of a guide when the stripe magnetic domain is extended during writing and reading of information. The guard pattern 7 prevents unwanted magnetic domains from entering the functional portion from the outside.

Patterns 5, 6 and 7 are patterns in which the magnetic garnet film (ferromagnetic film) 13 itself is made non-magnetic. The non-magnetized patterns 5, 6 and 7 are formed by laminating SiO or SiO ₂ in a thickness of 1 to ₂ μm on the magnetic garnet film (ferromagnetic material film) 13 by a sputtering method and forming a desired pattern shape by a photolithography method. Ion and H
The magnetic garnet film (ferromagnetic material film) 13 was demagnetized by separately irradiating it with ions to form it. These patterns may be groove patterns in which the magnetic garnet film (ferromagnetic material film) 13 is dug, and there was no problem in carrying out this example.

The conductor groups arranged above and below the functional portion are conductor groups for input / output of information. The conductor 9 is for writing Bloch line pairs, the conductor 10 is for reading / erasing Bloch lines, and the wide conductor 11 is for information. It was used to control the Bloch line at the time of input and output of. The conductors 9 and 10 were formed on the magnetic garnet film (ferromagnetic film) 13 with the insulating layer 14 interposed therebetween.
The insulating layer 17 was laminated thereon, and the conductor 11 was formed thereon. The Bloch line 3 existing in the domain wall 2 is a dummy Bloch line for keeping the Bloch line pair 4, which is an information carrier, stable. The pattern 8 is a pattern (bit pattern) for bit positioning of a Bloch line pair. This pattern is a pattern in which the thickness of the magnetic garnet film (ferromagnetic material film) 13 is periodically changed.

The cross-sectional structure of the portion 10 for reading and erasing the Bloch line is as shown in FIG. In this structure, the dimensions are determined as shown in FIG. When the respective values are determined so as to satisfy the following two equations, when a current having the same amplitude is applied in the opposite direction to each conductor of the conductor 10, the distribution of the magnetic field generated is as shown in the lower diagram of FIG. Become.

G ² + (g + 2a) ² > 8s (s + b) g ² (g + 2a) ² > 8s (s + b) {g ² + (g + 2a) ² +6 (s + b) ² + 2b ² } The stripe magnetic domain has a maximum vertical magnetic field component. Is cut, that is, at the center of the gap (x = 0 point). If there is an in-plane magnetic field component at the point where the stripe magnetic domain is cut, a horizontal Bloch line is generated by the in-plane magnetic field, which causes a malfunction. That is, in FIG. 3, a situation may occur in which the striped magnetic domain 1 having the Bloch line 3 is not cut and the striped magnetic domain 1'having no Bloch line is cut. Therefore, the read margin is narrowed. In the present embodiment, as shown in FIG. 2, the in-plane magnetic field component becomes 0 at the point where the vertical magnetic field component becomes maximum. Therefore, such a malfunction does not occur, and the read margin can be expanded. FIG. 5 shows read margins in the conventional technique and the present invention. In the present invention, the read current margin is expanded by 3 to 4 times as compared with the prior art.

Further, the thickness s of the spacer used in this embodiment is
Is more than 500 nm, the above two expressions can be satisfied so that the gap dimension g between the two parallel conductors for reading does not become the submicron dimension, and the fabrication of this parallel conductor is facilitated.

Since the two parallel conductors used in this embodiment have the same width and thickness and the same spacing as the magnetic garnet film, they can be formed by a simple manufacturing process. Further, since the amplitudes of the currents applied to the two parallel conductors are equal, no dedicated circuit is required.

According to this embodiment, the shape of the conductor can be quantitatively determined so that the magnetic field distribution is such that malfunctions are reduced when reading or erasing the Bloch line.
The parallel conductors, which are easy to fabricate, allow the read and erase margins to be expanded.

Further, by using the two parallel conductors of this embodiment for erasing the Bloch line, it was possible to expand the erasing margin.

[0023]

According to the present invention, the shape of the conductor can be quantitatively determined so that the magnetic field distribution is such that malfunctions are reduced when reading or erasing the Bloch line.
The parallel conductors, which are easy to fabricate, allow a large margin for reading and erasing. As a result, we were able to realize a highly versatile solid-state memory that has never existed before.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a storage portion of a Bloch line memory device for explaining an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a reading principle of a Bloch line.

FIG. 4 is an explanatory diagram of a conventional technique.

FIG. 5 is a read margin diagram.

[Explanation of symbols]

10 ... Conductor for reading and erasing, 11 ... Wide conductor, 12
... non-magnetic substrate, 13 ... magnetic garnet film (ferromagnetic material film), 14 ... insulating layer.

Claims (5)

[Claims] 1. A Bloch line using, as a carrier of information, a Bloch line pair present in domain walls of stripe magnetic domains arranged in parallel in a ferromagnetic film having an easy axis of magnetization perpendicular to the film surface. In the memory element, two parallel conductors formed on the ferromagnetic body via a spacer are used, the amplitude is equal to each of the parallel conductors, and a magnetic field generated when a reverse current is applied, A place where the vertical component on the surface of the ferromagnetic film takes a maximum value and a place where the in-plane component of the magnetic field on the surface of the ferromagnetic film becomes 0 are at least coincident, and the parallel conductor is A Bloch line memory device characterized in that a magnetic domain cutting operation is performed by using the Bloch line memory device. 2. A Bloch line memory in which a Bloch line pair present in domain walls of stripe magnetic domains arranged in parallel is used as an information carrier in a ferromagnetic film whose easy axis is a direction perpendicular to the film surface. In the element, two parallel conductors having a width a (width at the film thickness center), a thickness b, and an inter-conductor gap dimension g formed on the ferromagnetic film via a spacer having a thickness s are as follows. A Bloch line memory device characterized by satisfying the condition expressed by the equation. g ² + (g + 2a) ² > 8s (s + b) g ² (g + 2a) ² > 8s (s + b) {g ² + (g + 2a) ² +6 (s + b) ² + 2b ² } 3. A Bloch line memory device according to claim 1, wherein the gap between the two parallel conductors is 1 μm or more. 4. A Bloch line memory device, wherein at least two parallel conductors according to claim 1, 2 or 3 are applied to a part of a read operation in a Bloch line memory. 5. A Bloch line memory device in which two parallel conductors according to claim 1, 2 or 3 are at least applied to a part of an erase operation in a Bloch line memory.