JPS5998381A - Magnetic storage element - Google Patents

Abstract

PURPOSE:To generate effectively a regular minor loop by means of a desired number of stripe domains by arranging a bubble domain generator conductor pattern to a minor loop region taking the stripe domain as a unit. CONSTITUTION:A hair pin conductor 21 for stripe domain generation is arranged in the minor loop region and a bubble train is generated by flowing a current 23 to the conductor 21 under a bias magnetic field having a bubble applied with a prescribed bias magnetic field after the domain is cleared. Then, when the vertical magnetic field is reduced while applying a planar rotating field is applied vertically to the conductor 21, the train of the stripe domain 22 which takes the vertical Bloch line pair as storage information and becomes a minor loop is formed. Both ends of the domain 22 is cut by a current reverse to the current 23 of the conductor 21 and a cut current 25 of a parallel conductor 24 in common use with a transfer gate. Through the constitution above, the regular minor loop by the stripe domain of a desired number of the high density magnetic storage elements comprising the vertical Bloch line pair is generated effectively.

Description

[Detailed description of the invention] The present invention relates to magnetic memory elements.

The development of magnetic bubble elements is actively being carried out in various places with the aim of increasing density and speed, including permalloy devices, ion-implanted contiguous disk devices, current-driven devices, and so-called hybrid devices that combine these devices. It has been said that the limit to the high density of these devices lies in the photolithography technology used to form the bubble transfer path. However, in recent years, the technology has advanced rapidly. As a result, the issue of materials for increasing density, that is, to what extent the bubble diameter can be reduced, has become a problem. With the currently used garnet materials, the minimum attainable bubble diameter is said to be 0.3 μm. Therefore, a bubble material capable of retaining bubbles below 0.3 μm must be found in a material other than garnet material. This is not so easy, and this is even considered to be the limit of bubble densification.

On the other hand, as a memory element that can significantly improve the density limit based on the characteristics of the bubble retention layer and keep the information readout time at the same level as conventional elements, we have developed A pair of vertical float lines (hereinafter referred to as VBL) created in the Bloch domain wall around a stripe domain existing in a ferromagnetic film (including a ferrimagnetic film) with an easy magnetization direction is used as a storage information unit. Magnetic memory elements for use in Although this element can have both a shift register configuration and a major-minor configuration, FIG. 1 shows an overall view of the chip in the case of a major-minor configuration as an example.

To show the overall flow of information, first, the information written by the generator 1 (the presence or absence of bubbles) moves from the top to the bottom of the writing major line. In order to record this information in the minor loop 2, the minor loop' (Bloch that can hold i-vBL) is created so that the information on the major line indicated by the presence or absence of bubble 3 can be transferred to the minor loose in VBLO form. It is a sign of failure to be constructed with domain walls, and is the key to the dramatic increase in storage capacity.

The information (VBL) transferred to the write line transformer 7 agate 4 in a minor loose manner can move the striped domain domain wall that constitutes the minor loop. Information transfer from the minor loop to the read major line involves conversion from VBL to bubble. Note that this read transfer gate 5 also has a block replicator function.

In this way, by configuring the minor loose with striped domains existing in the bubble material and using VBL in place of the bubble domain as an information unit on the minor loose, it is possible to improve the structure compared to devices using conventional bubble domains. It is possible to achieve a storage density improvement of approximately two orders of magnitude.

The configuration example and operation of this element will be explained in more detail.

The major line uses a current drive method for both writing and reading. A write transfer gate consisting of four parallel conductors constitutes a bubble on the major line and a minor loose.

It uses interaction with the striped domain head.

When there is a bubble domain on the major line line, the heads of the stripe domains forming the minor loop connected to it move away from the bubble due to the repulsive interaction between the bubble and the stripe domain. When there is no bubble on the submerged major line, write VBLf: on the minor loose striped tome-in domain wall.

As a means of making VBL into a striped domain head,
Conductor connecting the striped domain head to it
The pattern is dynamically moved by applying a pulsed current to dynamically convert the head domain wall. This method creates two VBLs, which have different properties and are easy to recombine.

Therefore, in order to stabilize the information, an in-plane magnetic field is applied in the longitudinal direction of the striped domain, and the striped domain head is separated by two conductors on the striped domain side. Create a VBL of

VBLs with the same properties stably exist even if they approach each other.

The minor loose stripe domain head corresponding to the area where the bubble exists on the major line is separated from the conductor pattern due to the repulsion with the bubble, so no VBL is formed. As a result, the major line information '1'' is transferred with no VBL pair in the minor loose.

Within the minor loose, information is stored using a pair of VBLs with the same properties as one bit. The □VBL pair is used in consideration of the stability of the Lezurigater action.

A transfer pattern is set so that bits can be selectively transferred one by one to keep the bit period and VBL interval constant in the minor loop. - As an example, a parallel thin line pattern made of a permalloy thin film with a width So is formed on the striped domain constituting the minor loop in a direction perpendicular to the longitudinal direction of the striped domain, with a period twice as long as the stable interval So between VBLs. , the magnetic poles induced on both sides of the parallel wire and V
It utilizes interaction with BL.

One method for transferring VBL along the minor loose is to dynamically perform it by applying a pulsed bias magnetic field to the stripe domain. A readout transfer gate consisting of three parallel conductors converts the information stored as VBL in the striped domain domain wall forming the minor loop into a bubble, transfers it to the major line, and outputs the information on the minor loop. It also functions as a replicator to prevent information from being destroyed. The operating principle will be explained. One pit formed by a VBL pair is fixed to a stripe domain head by applying an in-plane magnetic field, for example.

A conductor pattern is then used to create a bubble between the striped domain head and the cut.

Then, the same VBL as the VBL with the cut portion removed is configured in the stripe domain head after the bubble cut portion is removed. Such a VBL replication effect occurs only for a VBL with a minus sign.

The bubble cut off from the minor loose striped domain head is transferred along the major line toward the detector. Here, it is utilized that the pulse current value that cuts the striped domain head is different depending on whether the striped domain head has VBL or not. If there is no VBL on the striped domain head, it will be difficult to cut. Therefore, if the stripe domain head has VBL, a bubble can be sent to the major line, but V
If there is no BL, there is no bubble. However, the presence or absence (1, 0) of VBL on the minor loop is converted to the presence or absence of a bubble on the read major line.

The elimination method for VBL pairs will be described. Place the VBL pair to be erased at the position closest to the minor loose stripe domain head on the convolution major line side. Next, the in-plane magnetic field H
Add 3p to the VBL pair you want to delete and its VBL pair.
Bring one half of the BL pair to the stripe domain head, and use the parallel conductor used to cut the positive VBL when writing information to cut the stripe domain head.After cutting the bubble domain] The VBL brought along with the VBL pair to be erased is replicated in the stripe domain head of. In the end, only the VBL pair that is desired to be erased will be erased. In addition, when clearing the entire minor loop, first erase all the stripe domains by increasing the bias magnetic field, and then form the minor loop drive domain from the S=1 bubble, so that all the pits are zero without the VBL being completely heated. It is possible to create a state of

In a magnetic memory element having such a structure having minor looseness, the most fundamental problem with this element is how to generate striped domains constituting minor loops. In other words, it is known that irregular labyrinth-like striped domains can exist in ordinary ferromagnetic films without an applied magnetic field, but there is no effective and efficient means to regularly generate any number of striped domains. is still not well known.

An object of the present invention is to provide a magnetic storage element having effective means for regularly generating striped domains forming each minor loop of the magnetic storage element using striped domains. That's true.

According to the present invention, in a magnetic memory element having a major-minor configuration in which a VBL pair in a Bloch domain wall at a stripe domain boundary is used as a unique information unit and the stripe domain is a unit of a minor loop, each of the minor loops is provided. A magnetic memory element is obtained in which a conductor pattern for generating bubble domains is provided on each minor loose so that after each bubble domain is generated, the applied bias magnetic field is reduced to form a stripe domain.

Hereinafter, the present invention will be explained in detail using Examples.

Example 1゜ FIG. 2 is a schematic diagram showing an embodiment of the present invention.

FIG. 2 partially shows the minor loop region of FIG. In this embodiment, a hairpin-shaped conductor 21 for generating stripe domains is formed in a minor loose region. To form the striped domains 22, a current 23 is passed through the hairpin-shaped conductor 21 under a bubble presence bias magnetic field, which is obtained by clearing the domains with a strong perpendicular magnetic field and then applying a constant perpendicular bias magnetic field, to generate a bubble array. Thereafter, by applying an in-plane magnetic field in a direction perpendicular to the conductor 21 and decreasing the perpendicular magnetic field, a row of striped domains 22 is obtained. At this time, it is conceivable that the stripe domains may extend and protrude from the conductor 21, but this can be prevented by passing a current in the opposite direction to the current 23 through the conductor 21 and cutting the stripe ends. Similarly, the two parallel conductors 24 at the right end in FIG. 2 serve to align the edges of other stripe domains by flowing a cut current 25. Note that the parallel conductor 24 can also be used as the readout transfer gate 5.

Embodiment 2 FIG. 3 is a diagram showing a second embodiment of the present invention. Here, a conductor pattern 3 that generates striped domains is shown.
A stripe pattern 32 is provided to keep the stripe domains parallel to each other. Since the stripe domains are stable at the ends of the stripe pattern, bubbles are easily generated by the conductor 31 having a structure that partially concentrates the current magnetic field. After generating bubbles, the applied perpendicular magnetic field is reduced in the same manner as in Example 1, thereby making it possible to transform the bubble array into a striped domain array.

Note that if the stripe pattern 32 has the properties of a soft magnetic material, bubbles can be generated more easily by applying an in-plane magnetic field parallel to the pattern 32 at the time of bubble generation.

Example 3, FIG. 4 is a diagram showing another embodiment of the present invention.

Here, a feature is that a hairpin-shaped conductor 41 having a different shape from the conductor 31 in Example 2 is provided as a bubble generator for forming stripe domains.

Example 4゜ FIG. 5 is a diagram showing another embodiment of the present invention.

Here, a metal pattern 51 which is basically the same as the hairpin-shaped conductor 21 for generating stripe domains in Example 1, but which serves to align the stripe domains by the magnetostrictive effect of the metal film of the stripe domain holding layer, is used as the conductor 2.
It is characterized by being extended from 1. This metal pattern 51 is also effective in the role of heat dissipation against an increase in Joule heat due to conductor current when a large-capacity element is fabricated.

As explained above, according to the present invention, a means for regularly generating a large number of striped domains is obtained, and it is possible to realize a large-capacity storage element using a magnetic storage element in which VBL pairs on a striped domain are stored information units. The effect is strong.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of a magnetic memory element chip that uses VBL pairs existing in Bloch domain walls on stripe domain boundaries as storage information units, Fig. 2 is a schematic diagram showing Example 1, and Fig. 3 is an implementation example. Schematic diagram showing Example 2, FIG. 4 is Example 3
FIG. 5 is a schematic diagram showing Example 4. 1...bubble generator, 2-minor loop, 3...bubble, 4--contained transfer gate, 5...
Readout transfer gate, 21... hairpin-shaped conductor, 22... striped domain, 23... nopull generated electric current υits 24-stripe domain cut conductor, 25... domain cut)% flow, 31... Conductor for bubble generation, 32... Striped domain holding pattern, 41... Hairpin-shaped conductor, 51... Metal pattern for aligning striped domains. Talent 〃 En? 3 z3(.o 5 Figure 2(

Claims (1)

[Claims] A Bloch domain wall around a stripe domain existing in a ferromagnetic film (including a ferrimagnetic film) that is equipped with information readout, convolution, and storage means and whose easy magnetization direction is perpendicular to the film surface. A vertical Ploch line pair consisting of 92 adjacent vertical Ploch lines created in the interior is used as a unique information unit, and the striped domain is a minor loose unit. A magnetic memory element having a major-minor configuration, characterized in that a bubble domain generator conductor pattern is provided in the minor loop region.