JPH0313674B2 - - 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 for a memory element that uses a soft magnetic film such as permalloy in a memory element as an information carrier 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 bubbles are attracted to the resulting magnetic poles and transferred. The so-called magnetic field drive method was common. However, with this magnetic field drive method, as the bubble diameter is made smaller to increase storage density, the in-plane rotating magnetic field required for bubble transfer increases rapidly, so the voltage applied to the in-plane rotating magnetic field generation coil increases. It is well known that this method has a major drawback in that it is not suitable 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 rotating magnetic field.

As a bubble transfer method that does not use a coil for generating an in-plane rotating magnetic field, there is already a current drive method (hereinafter referred to as the present invention) in which a bubble is driven by passing an alternating current through a meandering conductor line formed on a magnetic thin film. (referred to as the initial current drive method to distinguish it from the extremely new current drive method) has become publicly known. Although some improvements have been made to this initial current drive system, the shape of the conductor line is too complex, and the bubble's magnetism with magnetic thin pieces such as permalloy, which is essential for giving directionality to the bubble's motion, has been improved. Attempts to increase the memory density would significantly increase the power consumption of the device, making it impractical due to factors such as the need to transfer the bubble against the trapping force caused by the interaction.

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 recently been proposed. This two-layer conductor type current drive method requires the use of a much simpler opening pattern than the initial current drive method, so it is possible to dramatically improve storage density. However, the two-layer conductor type current drive system has serious drawbacks in that each of the two conductor layers must be driven independently, which increases power consumption and makes the peripheral circuit extremely complex. There is.

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

Before explaining the principle of the present invention, the general properties of magnetic materials will be described first. For example, the Journal of Applied Physics was published in October 1979 by 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. It is something.

FIG. 2 is a diagram showing the basic principle of the present invention.
In FIG. 2, 5 is a bubble, arrows 6 and 7 are the direction of the driving force applied to the bubble domain wall, 8 is the boundary of the tensile thin film pattern 4, and arrow 14 is the direction of the bias magnetic field. 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, FIG. 3, decreases as it approaches the thin film pattern boundary. Receives driving force in the direction shown by . 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 will not be able to stay at the position shown in Figure 2a, but will reach the stable position shown in Figure 2b, where the domain wall energy is minimum. Moving.

Next, the operating principle of the present invention based on the above-mentioned basic principle will be specifically explained using an example of implementation shown in FIG. FIG. 3a shows an example of the waveform of the current flowing through the conductor layer, and FIG. 3b shows an example of the transfer pattern of the present invention. In Figure 3a, the vertical axis 11 is the current value, the horizontal axis 10 is the time, 12 is the current waveform, 50,5
1, 52, 53, 54, 55, 56, 57, 5
8 represents each time on the horizontal axis 10. In Fig. 3b, the arrow 13 indicates the positive direction of the current, the arrow 14 indicates the direction of the bias magnetic field, 15 indicates the perforated transfer pattern provided in the tensile conductor layer, and 16 is formed facing the conductor layer. perforation pattern provided in a tensile non-magnetic thin film layer, 30, 31, 32, 3
3, 34, 35, 36, 37 represent the positions of bubbles.

When a bipolar current pulse as shown in Figure 3a is applied to the conductor layer, the bias magnetic field distribution (hereinafter referred to as , simply referred to as magnetic field distribution), and the position indicated by 30 becomes a magnetostatic bubble stable point (now, consider the position 30 to be the starting point of bubble transfer). During the next time between 51 and 52, no current flows through the conductor layer and the above magnetic field distribution disappears, so the bubble moves to position 31 based on the basic principle explained using Figure 2. do. During the next time period 52-53, the magnetic field distribution occurs again, so the bubble receives a driving force from the magnetic field gradient and moves to the position indicated by 32. During the next time period 53-54, the magnetic field distribution disappears and the bubble moves to position 33 based on the basic principle described above. In the next time between 54 and 55, both positions 30 and 34 become static magnetically stable points due to the magnetic field distribution, but the distance between 33 and 34 becomes 33 and 34.
Since it is smaller than the distance between 0 and 0, the bubble at position 33 receives a magnetic field gradient toward position 34 and moves to position 34. During the next time period 55-56, the magnetic field distribution disappears, so the bubble moves to the position of the bubble 35 based on the above-mentioned basic principle. Below, based on the same principle of operation, the bubbles are between 56-57 and 5.
It moves to positions 36 and 37 in the time between 7 and 58. The bubble is thus transferred from position 30 to position 37 in a time between 50-58.

That is, the single-layer conductor type current-driven magnetic bubble element of the present invention includes forming a single conductor layer having a perforated transfer pattern on a magnetic thin film having a non-zero magnetostriction constant capable of holding magnetic bubbles; A tensile or compressible non-magnetic thin film layer is formed facing the conductor layer so as to be isolated from each other and electrically insulated, and the transfer hole is formed in this tensile or compressible non-magnetic thin film layer. A perforated pattern or an island pattern is provided with respect to the pattern so that it has a slight positional shift in the direction of the alternating current flowing through the conductor layer, and magnetic bubbles are generated by the time-modulated magnetic field gradient generated by the alternating current. It is characterized by transferring.

Next, some other embodiments of the present invention will be shown. Fourth
The figure shows an embodiment in which the pattern is shaped like a key so that the zigzag transfer of bubbles as seen in the embodiment of FIG. 3 is avoided and the transfer is as straight as possible. In Figure 4, 5 is a bubble, 13
14 is the direction of the current flowing through the conductor layer, 14 is the direction of the bias magnetic field, 15 is the perforation pattern for transfer in the tensile conductor layer, 16 is the perforation pattern provided in the tensile nonmagnetic thin film layer, and 20 is the perforation pattern provided in the tensile nonmagnetic thin film layer. The arrow indicates the bubble transfer direction.

FIG. 5 is an example of an implementation using a compressible non-magnetic thin film layer. The domain wall energy distribution near the pattern boundary in a compressible nonmagnetic thin film layer is shown in Figure 1.3.
The distribution is like folding the domain wall energy distribution about the vertical axis 2. Therefore, when using a compressible non-magnetic thin film layer, by providing an island pattern that is inversely symmetrical to the perforated pattern, bubble formation can be achieved based on the same operating principle as explained using Fig. 3. transfer can be performed. In FIG. 5, 5 is a bubble, 13 is the direction of the current flowing through the conductor layer, 14 is the direction of the bias magnetic field, 15 is the perforated pattern for transfer in the tensile conductor layer, and 17
is an island pattern in a compressible non-magnetic thin film layer, 20
is the bubble transfer direction.

Various shapes of patterns in the conductor layer and non-magnetic thin film layer are conceivable in addition to the embodiments shown in FIGS. 3, 4, and 5, but the shapes explained using FIG. Any shape that can transfer bubbles according to the principle of operation is included in the present invention.
Various methods can be used to form the perforated pattern for transfer in the conductor layer and the perforated pattern in the nonmagnetic thin film layer, such as wet chemical etching, plasma etching, and anodic oxidation. It goes without saying that any method of formation that produces the same effect is included in the present invention.

[Brief explanation of the drawing]

FIG. 1 is part of the explanatory diagram shown in the paper by El Schulz et al. FIG. 2 is a diagram showing the basic principle of the present invention. FIG. 3 is a diagram specifically illustrating the operating principle of the present invention using an example of implementation. FIGS. 4 and 5 are diagrams showing embodiments of the present invention. In the figure, 1 is the horizontal axis showing the position of the domain wall, 2 is the vertical axis showing the domain wall energy, 3 is the domain wall energy distribution, 4 is the tensile thin film pattern, 5 is the bubble,
6 and 7 are the directions of the driving force applied to the bubble domain wall, 8 is the boundary of the thin film pattern, 10 is the horizontal axis indicating time, 1
1 is the vertical axis representing the current value, 12 is the current waveform, 13
The arrow indicates the direction of the current flowing through the conductor layer, 14 indicates the direction of the bias magnetic field, 50, 51, 52, 53, 54,
55, 56, 57, 58 are each time on the horizontal axis 10,
30, 31, 32, 33, 34, 35, 36, 3
7 is the position of the bubble, 15 is the perforation pattern for transfer provided in the tensile conductor layer, 16 is the perforation pattern provided in the tensile non-magnetic thin film layer, and 17 is the perforated pattern in the compressible non-magnetic thin film layer. This is an island-like pattern.

Claims (1)

[Claims] 1. Forming a conductor layer with a transfer perforation pattern on a magnetic thin film having a non-zero magnetostriction constant capable of holding magnetic bubbles, and further comprising means for applying an alternating current to the conductor layer, and further comprising means for applying an alternating current to the conductor layer. A tensile or compressible non-magnetic thin film layer is formed facing the conductor layer so as to be mutually isolated and electrically insulated, and the transfer hole is formed in this tensile or compressible non-magnetic thin film layer. 1. A single-layer conductive current-driven magnetic bubble element, characterized in that a perforated pattern or an island-like pattern is provided with a slight positional shift in parallel to the direction of application of alternating current to the conductor layer with respect to the pattern.