JPH0232707B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current-driven magnetic bubble element. Magnetic bubble (hereinafter simply referred to as bubble)
The bubble transfer method in a memory element that uses a soft magnetic film such as permalloy in a memory element is to sequentially magnetize a chevron-shaped or Y-shaped pattern made of a soft magnetic film such as permalloy using an in-plane rotating magnetic field applied from the outside. The so-called magnetic field drive method, in which bubbles are attracted to the resulting magnetic poles and transferred, has been common. However, with this magnetic field drive method, as the bubble diameter is reduced to increase storage density, the in-plane rotating magnetic field required for bubble transfer increases rapidly, resulting in increased power consumption and the ability to generate in-plane rotating magnetic fields. It is well known that this method has a major disadvantage in that the voltage applied to the coil increases, making it unsuitable for high-speed transfer. In order to overcome these drawbacks of the magnetic field drive system, it is necessary to realize a bubble transfer system that does not use a coil for generating an in-plane magnetic field.

As a bubble transfer method that does not use an in-plane magnetic field generating coil, a conductor line already formed on a magnetic thin film is a current drive method (hereinafter referred to as an extremely new current drive method to which the present invention relates) in which a conductor line formed on a magnetic thin film is used to drive a bubble by passing an alternating current. (referred to as the initial current drive method to distinguish it from the drive method) is well known. Although some improvements have been made to this initial current drive system, the shape of the conductor line is too complex, and the magnetic connection between the permalloy thin piece and the bubble, which is essential for giving directionality to the bubble motion, is a problem. Due to factors such as the need to transfer bubbles against the trapping force caused by interactions, attempts to increase storage density significantly increase the power consumption of the device, making it impractical.

In order to overcome these drawbacks that cannot be avoided with the magnetic field drive method and the initial current drive method, a new current drive method called a two-layer conductor type current drive method has been proposed in recent years. In this two-layer conductor type current drive method, a much simpler opening pattern can be used than in the initial current drive method, so that the storage density can be dramatically improved.

However, the two-layer conductor type current drive system has the serious drawbacks of extremely high power consumption and extremely complex peripheral circuits because each of the two conductor layers must be driven independently. are doing.

An object of the present invention is to provide a single-conductor current-driven magnetic bubble element that can transfer bubbles with as little current as possible using a very simple peripheral circuit.

Before explaining the principle of the present invention, the following general properties of magnetic materials will be described. For example, in October 1979, L. Schltz et al.
Applied Physics) Vol. 50 No. 11 No. 7862-No.
As described in the paper published on page 7864, the domain wall energy changes as shown in Figure 1 at the edge of a tensile thin film pattern provided on a magnetostrictive bubble material. In FIG. 1, the horizontal axis 1 indicates the position of the domain wall, the vertical axis 2 indicates the domain wall energy, 3 indicates the domain wall energy distribution, and 4 indicates the tensile thin film pattern.

The present invention is based on the following principle that utilizes the properties of the above-mentioned magnetic materials, and eliminates the serious drawbacks of conventional current drive systems such as the initial current drive system and the two-layer conductor type current drive system. be.

FIG. 2 is a diagram showing the basic principle of the present invention.
In FIG. 2, arrows 5 for bubbles 6 and 7 indicate the direction of the driving force applied to the bubble domain wall, and 8 indicates the direction of the bias magnetic field at the boundary 14 of the tensile thin film pattern. When the bubble is at the position shown in Fig. 2a, on the right side of the thin film pattern boundary, the domain wall energy shown in Fig. 1 3 decreases as it approaches the thin film pattern boundary, so the bubble domain wall on the right side of the thin film pattern boundary is shown by arrow 7. Receives driving force in the direction shown. On the left side of the thin film pattern boundary, the domain wall energy decreases as the distance from the thin film pattern boundary increases, so the bubble domain wall on the left side of the thin film pattern boundary receives a driving force in the direction shown by arrow 6.

Therefore, the bubble as a whole receives a driving force that directs it toward the inside of the thin film pattern. Therefore, if no external force is acting on the bubble, the bubble cannot stay at the position shown in Figure 2a, but moves to the position where the domain wall energy is minimum, that is, the stable position shown in Figure 2b. do.

Next, the operating principle of the single-layer conductive current-driven magnetic bubble element of the present invention based on the above-mentioned basic principle will be illustrated in an easy-to-understand model using FIG.

3a, 3b, 3c, and 3d, the vertical axis 11 is the current value, the horizontal axis 10 is the time, 12 is the current waveform, 50, 51, 52, 53, 54, 5
5, 56, 57, represent each time on the horizontal axis 10.

In Figure 3a, Figure 3b, Figure 3c, and Figure 3d, 5 is a bubble, arrows 13 and 17 are the direction of current, arrow 14 is the direction of the bias magnetic field, and 15 is a tensile conductor layer. The transfer perforation pattern 16 provided inside is a perforation pattern provided in a tensile nonmagnetic thin film layer formed facing the conductor layer.

When a bipolar current pulse as shown at 12 in FIG. 3a is applied to the conductor layer, 50-5 in FIG.
During the time period of 1 hour, a bias magnetic field distribution occurs due to current disturbance due to the perforation pattern for transfer, so the position shown in FIG. 3b becomes the stable point of the bubble. During the next time period 51-52, no current flows in the conductor layer and the bias magnetic field distribution caused by the current disturbance disappears, so the bubble is generated based on the basic principle explained using Fig. 2. Move to the position shown in Figure 3c. In the next time period 52-53, the bias magnetic field distribution due to the current disturbance occurs again, so the bubble receives a driving force from the magnetic field gradient and moves to the stable point shown in FIG. 3d.
In the next time period 53-54, the bias magnetic field distribution caused by the current disturbance disappears, so the bubble moves to the position shown in FIG. 3e based on the above-mentioned basic principle.

Therefore, by continuously applying a bipolar current pulse train as shown in FIG. 3a to the conductor layer, a perforated transfer pattern as shown in FIG. Bubbles can be stably transferred along the transfer path defined by the open pattern.

That is, the single-layer conductor type current-driven magnetic bubble element of the present invention has a single conductor layer provided with a row of transfer hole perforations arranged periodically on a magnetic thin film capable of holding magnetic bubbles, and A tensile or compressible non-magnetic thin film layer having a perforated pattern row or an island pattern row having the same period as the perforation pattern row is isolated from the conductor layer and faced to each other so as to be electrically insulated. It is characterized in that magnetic bubbles are transferred by a time-modulated magnetic field gradient generated by an alternating current flowing through the conductor layer.

Next, an embodiment of the present invention will be shown using FIG.

In FIG. 4, the arrow 20 indicates the direction of the bipolar pulse current flowing through the conductor layer, the arrow 14 indicates the direction of the bias magnetic field, and 5 indicates the bubble. In the embodiment shown in FIG. 4a, 15 is a tensile conductor layer formed on a magnetic thin film capable of retaining bubbles, and a transfer perforation pattern 16 is formed on the upper side of the conductor layer, facing the conductor layer. This is a perforated pattern formed in a tensile non-magnetic thin film. Based on the embodiment shown in Figure 4a, a tensile conductor layer with a thickness of about 2500 Å is
An AlCu alloy was formed by vapor deposition, and an AlCu alloy of about 6000 Å was formed by vapor deposition facing the conductor layer with a spacer of about 1500 Å interposed therebetween to actually fabricate the single-layer conductive current-driven magnetic bubble element of the present invention. It was also experimentally confirmed that bubbles were stably transferred at a driving current of 3 mA/μm. FIG. 4b shows an example of an implementation using an island pattern 25 in a compressible non-magnetic thin film. When a compressible non-magnetic thin film is used, the domain wall energy distribution near the pattern boundary becomes a distribution similar to the domain wall energy distribution 3 in FIG. 1 folded about the vertical axis 2. Therefore, when using a nonmagnetic thin film, the bubble transfer is performed based on the same operating principle as that explained using FIG. 3 by making the pattern into an island pattern. be able to. FIG. 4c is an embodiment in which the pattern shape of FIG. 4a is made into an ellipse. In FIG. 4c, 26 is an elliptical perforation pattern for transfer provided in the tensile conductor layer, and 27 is an elliptical perforation pattern provided in the tensile nonmagnetic thin film. When an elliptical pattern is used in this way, the pattern boundary will have a certain curvature, but the domain wall energy distribution on the central axis of the elliptical pattern row is qualitatively similar to the domain wall energy distribution 3 in Figure 1. are equal, so bubble transfer can be performed using the same operating principle as explained using FIG.

Although various shapes of patterns in the conductor layer and nonmagnetic thin film are conceivable in addition to the example shown in FIG. 4, bubbles can be transferred based on the operating principle as explained using FIG. It goes without saying that any shape that can be obtained is included in the present invention. Furthermore, it goes without saying that either a conductor or an insulator material may be used as the nonmagnetic thin film.

[Brief explanation of drawings]

FIG. 1 is part of the illustration shown in the paper by El Schulz et al. Horizontal axis 1 is the position of the domain wall,
The vertical axis 2 indicates the domain wall energy, 3 indicates the domain wall energy distribution, and 4 indicates the tensile thin film pattern. FIG. 2 is a diagram showing the basic principle of the present invention. 4 is a tensile thin film pattern, 5 is a bubble, 6,
Reference numeral 7 indicates the direction of the driving force applied to the bubble domain wall, 8 indicates the boundary of the thin film pattern, and arrow 14 indicates the direction of the bias magnetic field. FIG. 3 is a diagram illustrating the operating principle of the present invention in an easy-to-understand model. Horizontal axis 10 is time, vertical axis 11 is current value, 12 is current waveform, 50, 51, 5
2, 53, 54, 55, 56, 57 are each time on the horizontal axis 10, 5 is the arrow of the bubbles 13 and 17, the direction of the current is the direction of the current, the arrow of 14 is the direction of the bias magnetic field,
15 is a perforated pattern for transfer provided in the tensile conductor layer, and 16 is a perforated pattern provided in the tensile nonmagnetic thin film. FIG. 4 is a diagram showing an embodiment of the present invention. 5 is the bubble, 14 arrow is the direction of the bias magnetic field, 20
The arrow indicates the direction of the current, 15 is a perforation pattern provided in a tensile conductor layer, 16 is a perforation pattern provided in a tensile nonmagnetic thin film, and 25 is a perforation pattern provided in a compressible nonmagnetic thin film. The island pattern 26 is an elliptical perforation pattern for transfer ellipse provided in the tensile conductor layer, and 27 is an elliptical perforation pattern provided in the tensile nonmagnetic thin film.

Claims (1)

[Claims] 1. On a magnetic thin film having a non-zero magnetostriction constant capable of holding magnetic bubbles, a single conductor layer with a row of perforated transfer patterns arranged periodically is formed, and the conductor layer has the same period as the perforated pattern rows for transfer. A tensile or compressible non-magnetic thin film layer having a perforated pattern row or an island pattern row is formed facing the conductor layer so as to be isolated from each other and electrically insulated, and an alternating current is applied to the conductor layer. A single-layer conductive current-driven magnetic bubble device characterized in that magnetic bubbles are transferred by a time-modulated magnetic field gradient generated by an electric current.