JPH0458674B2 - - Google Patents

Description

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

Magnetic bubble devices are being actively developed in various places with the aim of increasing density and speed, including permalloy devices, ion-implanted continuous disk devices, current drive 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, ie, how small the bubble diameter can be made, has become a problem. With currently used garnet materials, the minimum achievable bubble diameter is
It is said to be 0.3μm. Therefore, it is necessary to find a bubble material other than garnet material that retains bubbles with a diameter of 0.3 μm or less. 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 Adjacent perpendicular Blotsho lines (hereinafter referred to as
It's called VBL. ) pairs are provided as a unit of storage information. Although this element can have both a shift register configuration and a major-minor configuration, FIG. 1 shows an overall chip diagram of a major-minor configuration as an example.

To show the overall information flow, first, the information written by the generator 1 (the presence or absence of bubbles) moves from the top to the bottom of the write major line. In order to store this information in the minor loop 2, the minor loop is configured with a Brochu domain wall that can hold VBL so that the information on the major line indicated by the presence or absence of bubble 3 can be transferred to the minor loop in the form of VBL. This is a feature of the present invention, and is an important key to dramatically improving storage capacity.
Information transferred to the minor loop by write line transfer gate 4 (VBL)
can move on the striped domain domain walls that constitute the minor loop. Information transfer from the minor loop to the read major line involves conversion from VBL to bubble. In addition,
This read transfer gate 5 also has a block replicator function.

In this way, the minor loop is composed of striped domains existing in the bubble material, and the information unit on the minor loop is replaced by the bubble domain.
By using VBL, storage density can be improved by approximately two orders of magnitude compared to devices using conventional bubble domains.

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 forms a bubble on the major line and a minor loop.
It uses interactions with striped domain heads. When there is a bubble domain on the major line, the head of the stripe domain that forms the minor loop connected to it takes advantage of the fact that it moves away from the bubble due to the repulsive interaction between the bubble and the stripe domain. When there is no bubble on the write major line, write VBL to the stripe domain domain wall of the minor loop.
As a means of creating a VBL in a striped domain head, the striped domain head is dynamically moved by applying a pulse current to the conductor pattern in contact with it, and the head domain wall is dynamically converted. This method creates two VBLs, but
These 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 VBL.
VBLs with the same properties remain stable even when they are close to each other. The stripe domain head of the minor loop, which corresponds to where the bubble exists on the major line, is away from the above conductor pattern due to the repulsion with the bubble, so the VBL
is not formed. As a result, the information "1" on the major line is transferred with no VBL pair in the minor loop.

In the minor loop, information is stored using a pair of VBLs with the same properties as one bit. A VBL pair is used considering the stability of the replicator action.
A transfer pattern is set so that the bit period in the minor loop, that is, the VBL interval, can be kept constant and selectively transferred one bit at a time. As an example,
On the striped domain constituting the minor loop above, a parallel fine line pattern made of permalloy thin film with a width S _{0 is formed in the direction perpendicular to the longitudinal direction of the striped domain, with a period twice the stable interval S 0 between} VBL, and parallel It utilizes the interaction between the magnetic poles induced on both sides of the thin wire and VBL.

One way to dynamically transfer VBL along the minor loop is 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 and transfers it out to the major line, and also transfers the information on the minor loop. It also functions as a replicator to prevent destruction. The operating principle will be explained. One bit formed by the VBL pair is fixed to the striped domain head by applying an in-plane magnetic field, for example.
The striped domain head is then cut out into a bubble using a conductor pattern. Then, after cutting the bubble, the striped domain head will have the same shape as the cut VBL.
VBL is regenerated. Such a VBL replication effect occurs only for VBLs with a minus sign. Bubbles cut from the striped domain head of the minor loop are transferred along the major line toward the detector. Here, we utilize the fact that the pulse current value that cuts off the stripe domain head differs depending on whether the stripe domain head has VBL or not. If there is no VBL on the striped domain head, it will be difficult to cut.
Therefore, VBL on the striped domain head
If there is, a bubble can be sent to the major line, but if there is no VBL, there is no bubble. In other words,
The presence or absence of VBL (1, 0) on the minor loop is converted to the presence or absence of a bubble on the read major line.

We will discuss the elimination method for VBL pairs. I want to delete
Place the VBL pair at the position closest to the stripe domain head of the minor loop on the write major line side. Next, I want to add an in-plane magnetic field Hip and erase it.
Bring the VBL pair and one half of the adjacent VBL pair to the striped domain head, and cut off the striped domain head using the parallel conductor used to cut off the positive VBL when writing information.Cut off the bubble domain. In the striped domain head after the
The VBLs brought with the VBL pair are replicated. In the end, only the VBL pair that you want to erase will be erased. In addition, when clearing the entire minor loop, first increase the bias magnetic field to erase all striped domains, and then set S = 1.
By forming a minor loop stripe domain from a bubble, it is possible to create an all-bit zero state with no VBL.

In a magnetic memory element having such a structure having a minor loop, the most fundamental problem with this element is how to generate striped domains constituting the minor loop. 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 memory element having an effective means for regularly generating stripe domains forming each minor loop in each minor loop of the magnetic memory element using striped domains.

According to the present invention, in a magnetic memory element having a major-minor configuration in which a VBL pair in a Blotsho domain wall at a stripe domain boundary is used as a storage information unit and the stripe domain is a unit of a minor loop, each of the minor loops A magnetic memory element is obtained in which a conductive pattern for bubble domain generation is provided on each minor loop 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.

Embodiment 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 the minor loop region. To form the striped domain 22, the hairpin-shaped conductor 2 is formed under a bubble-presence bias magnetic field in which a constant perpendicular bias magnetic field is applied after clearing the domain with a strong perpendicular magnetic field.
1 to generate a bubble train. 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 striped domains may extend and protrude from the conductor 21, but this can be avoided by passing a current in the opposite direction to the current 23 through the conductor 21 and cutting off the ends of the stripes. Similarly, the two parallel conductors 24 at the right end in FIG. 2 serve to align the ends 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 31 for generating striped domains and a striped pattern 32 for holding the striped domains in parallel are provided. 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 when 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 when generating bubbles.

Embodiment 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.

Embodiment 4 FIG. 5 is a diagram showing another embodiment of the present invention. Here, a metal pattern 51 is basically the same as the hairpin-shaped conductor 21 for generating striped domains in Example 1, but a metal pattern 51 is formed from the conductor 21 to align the striped domains by the magnetostrictive effect of the metal film of the striped domain holding layer. It is characterized by being stretched out. This metal pattern 51 is
It is also effective in the role of heat dissipation against the increase in Joule heat due to conductor current in the case of large-capacity elements.

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 large.

[Brief explanation of the drawing]

Figure 1 is an overall configuration diagram of a magnetic memory element chip that uses VBL pairs existing in the Blotzhoe domain wall on the stripe domain boundary as a storage information unit, Figure 2 is a schematic diagram showing Example 1, and Figure 3 is an implementation example. A schematic diagram showing Example 2, FIG. 4 is a schematic diagram showing Example 3, and FIG. 5 is a schematic diagram showing Example 3.
The figure is a schematic diagram showing Example 4. 1...Bubble generator, 2...Minor loop,
3...Bubble, 4...Write transfer gate, 5...Read transfer gate, 21...
... Hairpin-shaped conductor, 22 ... Stripe domain, 23 ... Bubble generation current, 24 ... Stripe domain cut conductor, 25 ... Domain cut current, 31 ... Bubble generation conductor, 32 ... Stripe domain holding pattern, 41 ... Hairpin-shaped conductor, 51 ... Metal pattern for aligning striped domains.

Claims (1)

[Claims] 1 In the Blotsho domain wall around the stripe domain existing in a ferromagnetic film (including a ferrimagnetic film) that is equipped with information read, write, and storage means and whose easy magnetization direction is perpendicular to the film surface. A major minor using a created vertical blotsho line pair consisting of two adjacent vertical blotsho lines as a storage information unit, having means for transferring the vertical blotsho line within a blotsho domain wall, and using the stripe domain as a unit of a minor loop. 1. A magnetic memory element according to the present invention, wherein a bubble domain generator conductor pattern is provided in the minor loop region.