JPH04105290A - Magnetic storage element and its manufacture - Google Patents

Abstract

PURPOSE:To improve the storage density by sectioning a ferromagnetic material film in stripes whose width is much less than the film thickness of the ferroelectric material film. CONSTITUTION:Striped grooves which are as deep as a magnetic garnet film is thick and have a constant period are formed at right angles to the in-surface easy-axis direction of the film. Namely, the grooves are formed and the striped areas 1 which are sectioned with the grooves are regarded as rectangular thin layers which have long sides in the length direction of striped film sectioning and short sides in the film thickness direction. The rectangular thin layers have uniaxial magnetic anisotropy at right angles to the layer, so magnetic domains 3 are formed and storage areas including their magnetic walls as transfer paths are formed. The length direction of the transfer paths of the magnetic domains 3 is perpendicular to the film surface. Consequently, data which is stored as a Bloch pair can be transferred from the film surface to the substrate side 4 and returned from the substrate side to the film surface reversely, thereby improving the recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a nonvolatile ultra-high density solid state magnetic memory element.

(Prior Art and Problems to be Solved by the Invention) Magnetic bubble devices are being actively developed in various places with the aim of producing high-density solid-state magnetic storage devices. However, with the currently used garnet materials, the minimum attainable bubble diameter is 0.3
It is said to be □m. Therefore, a bubble material that retains bubbles with a diameter of 0.3 μm or less must be found other than garnet material. This is not easy and is even considered to be the limit of bubble density.

It is easy to magnetize in the direction perpendicular to the film surface as an ultra-high-density magnetic memory element that greatly improves the density limit based on the characteristics of the bubble retention layer and can maintain information readout time at the same level as conventional elements. A perpendicular Bloch line (hereinafter simply referred to as a Bloch line) that exists statically and stably within a Bloch domain wall that forms the boundary of a striped domain formed in a soft magnetic ferromagnetic material (including ferrimagnetic material) film with a certain direction. A device using a pair of Bloch lines as a storage unit was invented (Japanese Patent Application No. 182346/1983).

In this device, it is difficult with current technology to input and output information by direct writing or reading of Bloch lines. Data input is performed by generating bubbles in a bubble generator using a generation, transfer, and detection technique (referred to as ), and the bubbles are transferred on a bubble transfer path and converted into Bloch lines at a conversion gate. Also, when reading, after converting the Bloch line into a bubble at the conversion gate,
The configuration is such that bubbles are transferred on a bubble transfer path and read out by a bubble detector 8.

This storage element typically uses
An element configuration called a major/minor configuration as shown in FIG. 2 is adopted. That is, a data string of bubbles written one after another by a bubble generator provided at the end of the major line, which is the first transfer path, is transferred on the major line transfer path, and then positioned at right angles to the major line,
In order to transfer data to a transfer path called a minor loop, which is a second transfer path that transfers multiple Fronho lines, data is converted in parallel from bubbles to Bloch lines using conversion gates installed at the ends of each minor loop. be done. At the time of reading, the Bloch line located at the conversion gate section at the end of the minor loop is converted into a bubble by the conversion gate. The converted bubble is transferred on the major line, detected by a bubble detector at the end of the major line, and output as data. 5 and 7 in the figure are respectively Bloch line writing/
This is a read conductor and a major line bubble domain transfer conductor.

However, even in a memory element with such a new configuration, the storage density is limited due to limitations on the characteristics of the garnet film.
It is limited to several gigabits per cm2. Recent improvements in digital image processing technology have begun to require storage elements with larger storage capacity and storage density.

The present invention has been made in view of these points, and its object is to provide a magnetic memory element having a memory density one order of magnitude higher than that of a conventional magnetic memory element using Bloch lines as information carriers.

(Means for Solving the Problems) That is, the present invention has an information reading means, an information writing means, and an information storage means, and a soft magnetic ferromagnetic material (ferrimagnetic material) having an easy magnetization direction in one direction within the film surface. The film (containing a magnetic substance) is divided by trenching to the depth of the film thickness in a striped pattern, and the magnetic domains that are generated in the divided film and are oriented in the in-plane direction are used as transfer paths, and the adjacent magnetic domains that occur within the magnetic domain are A vertical Bloch line pair consisting of two vertical Bloch lines is used as an information carrier, and has a function of writing and reading the Bloch line,
and a magnetic memory element in which the longitudinal direction of the magnetic domains is perpendicular to the film surface, and the soft magnetic ferromagnetic film has uniaxial anisotropy in the film surface in a direction perpendicular to the direction of the striped sections. It is.

That is, compared to the conventional magnetic memory element using Bloch lines as information carriers, the present invention has a similar storage density within the film surface, and also stores multiple bits of information in the direction perpendicular to the film surface. By inventing a structure that can take a three-dimensional structure, the present invention provides a magnetic memory element having a memory density ten times or more that of the conventional one.

(Example) Hereinafter, the present invention will be explained in detail with reference to Examples. Film thickness: 4.4□m, in-plane uniaxial magnetic anisotropy constant: 200.000
A magnetic garnet film with an erg/cm3.4yrMs of 1430G is used, and striped grooves with a width of 0.2 □m, a depth equal to the film thickness, and a pitch of 0.5 □m are formed in the film. The direction in which the striped grooves are formed is perpendicular to the in-plane easy axis direction of the film. This groove can be formed by implanting ions into the garnet film in the groove forming portion and then etching it with heated phosphoric acid.

FIG. 1 is a diagram showing the main part of the present invention. By forming the striped grooves, the striped region 1 divided by the grooves appears to be a rectangular thin layer, with the long side of the striped film section being the long side of the rectangle and the short side of the rectangle being in the thickness direction. You will be able to understand it. At this time, the stripe width of 0.311 m can be regarded as the thickness of a rectangular thin layer. Since this rectangular thin layer has uniaxial magnetic anisotropy in the direction perpendicular to the layer, a magnetic domain 3 can be formed, and a storage area can be formed using the domain wall as a transfer path. By making the longitudinal direction of the transfer path by this magnetic domain perpendicular to the film surface, data stored as Bloch line pairs is transferred from the film surface to the substrate side 4, and conversely back from the substrate side to the film surface. be able to. The transfer method uses a period of 0.1μ between rectangular thin layers.
Forming a chromium conductor layer 6 with a thickness of 0.05 μm in m periods,
This is done by forming a bit fixing pattern and applying a pulsed magnetic field in a direction perpendicular to the rectangular thin layer.

Information is basically written using the same method as in the conventional example. A major line 7 for bubble domain transfer is provided on the surface side of the rectangular thin layer, and data by bubbles transferred from the major line is transferred into the minor loop transfer path. Convert as Bloch line. At this time, the edge of the domain, which is the minor loop transfer path, is extended, and when there is no bubble in the major line, the domain is easily extended, and by applying a pulse current to the conductor 5 at the domain extension part, the rectangle is A perpendicular pulsed magnetic field is generated in the thin layer to cut the domain while generating positive and negative Bloch lines, and two negative Bloch lines are written. When there is a bubble on the major line, the minor loop end will not stretch,
No further writing occurs.

The readout method is the same as the conventional method, that is, the tip of the transfer path is extended, and the difference in the current value of the conductor 5 required for domain cutting is detected by utilizing the fact that the state of the domain wall at the tip varies depending on the presence or absence of a Bloch line. Reading can be performed.

As described above in detail using the embodiments, the present invention makes it possible to provide a magnetic memory element having a memory density that is one order of magnitude higher than that of the prior art, and contributes to the practical application of large-capacity magnetic memory elements.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of a magnetic memory element according to the present invention, and FIG. 2 is a diagram showing a conventional magnetic memory element. In the figure, 1 is a rectangular thin layer, 2 is an easy direction of in-plane-axial magnetic anisotropy, 3 is a transfer path formed by a domain formed in a rectangular thin layer,
4 is a soft magnetic ferromagnetic thin film substrate, 5 is a Bloch line writing/continuation conductor, 6 is a bit fixed pattern thin layer,
7 is a major line bubble domain transfer conductor, 8 is a data output section, and is a bubble generation and bubble detection section.

Claims (4)

[Claims] (1) A soft magnetic ferromagnetic material (including ferrimagnetic material) film having an information reading means, an information writing means, and an information storage means and having one direction in the film surface as an easy magnetization direction. By dividing the ferromagnetic film into stripes whose width is sufficiently small compared to the thickness of the ferromagnetic film, the in-plane magnetic domains generated in the divided film are used as transfer paths, and the phases generated within the magnetic domains are A magnetic memory element characterized in that a vertical Bloch line pair consisting of two adjacent vertical Bloch lines is used as an information carrier, and has a function of writing and reading the Bloch lines. (2) The magnetic memory element according to claim 1, wherein the longitudinal direction of the magnetic domain is perpendicular to the film surface. (3) Claims 1 or 2, characterized in that the soft magnetic ferromagnetic film has uniaxial anisotropy in a direction perpendicular to the longitudinal direction of the striped sections within the film plane. The magnetic memory element described in . (4) The magnetic memory element according to claim 1, wherein the soft magnetic ferromagnetic film is divided by forming striped grooves with a depth equal to the film thickness of the film. manufacturing method.