GB2041680A - Magnetic Bubble Device - Google Patents

Abstract

A magnetic bubble device has a transfer-in gate for a minor loop. Opposing surfaces of respectively an arm 23 of the element 18 of the minor loop nearest the transfer-in gate and an arm 24 of the element of the transfer-in gate nearest the minor loop are inclined to each other, e.g. at an angle between 30 DEG and 90 DEG . As a result, the risk that a magnetic bubble leaves its correct path or is annihilated is reduced, and the propagation margin of the bias field can be increased. <IMAGE>

Description

SPECIFICATION Magnetic bubble device This invention relates to a magnetic bubble device.

The principle of magnetic bubbles was discovered by Andrew H. Bobeck, and details are given by A.H.

Bobeck et al. in "Magentic Bubbles", Scientific American, Vol. 224, June 1971, pp. - 91. Memory devices wherein the existence or nonexistence of a magnetic bubble is caused to correspond to a signal are extensively utilized nowadays, and such devices have increasingly large capacities and high increasing speed of operation with the progress of magentic bubble technology.

A device of this kind is usually a chip having a layer of high permeability which has a suitable pattern and which is separated by an insulation layer to form a sheet of magnetic material in which magnetic bubbles are propagated. A magnet applies a bias magnetic field in the direction perpendicular to the chip, and a coil applies a magnetic field which rotates in a plan parallel to the chip. Ordinarily, the magnetic bubble is generated by a magnetic field established by current flowing through a hairpinshaped conductor disposed on the chip, is propagated along a write major line by the rotation of the rotating magnetic field, and is put into storage through a transfer-in gate into a minor loop which constitutes a memory portion.

In one kind of device, it is possible to perform simultaneously through a single gate the operation of (a) shifting a magnetic bubble corresponding to new information to be written from the write major line to the minor loop and (b) shifting the magnetic bubble already in the minor loop and corresponding to old information to be annihilated from the minor loop to the write major line. Such a gate is called a "swap gate". In a swap gate, the path of the magnetic bubble corresponding to the new information fulfils the function of a transfer-in gate. Accordingly, although the present invention is principally described as applicable to a transfer-in gate, it is similarly applicable to swap gates.

A swap gate is described in, for example, U.S.A.

Patent No. 4,007,453. Figure 1 of the drawings accompanying the present application is a plan view of such a swap gate and shows five permalloy elements 2,3,4,5,6 at the right-hand end of a minor loop 1. With the rotation of a rotating magnetic field, magnetic bubbles are propagated along the minor loop 1 in the direction of the arrow 7. The magnetic bubbles are generated by a magnetic bubble generator (not shown), and are propagated along a write major line 8 in the direction of the arrow 9.If, upon arrival of the magnetic bubble at the upper end A of a permalloy element 10, current is caused to flow through a conductor loop 11 which is in a layer different from that providing the element 10 in the dip action of the arrows 12, the magnetic bubble leaves the upper end A of the element 10 and passes 'through a permalloy element 13 to the element 3 of the minor loop 1.

In a gate for transfer-in only, except that neither of the elements 14 and 15 for transferring the magnetic bubbles from the minor loop 1 to the write major line 8 is present, the operating principle is just the same as shown in Figure 1.

As Figure 1 shows, the opposing surfaces B and C of respectively the element 4 of the minor loop 1 nearest the transfer-in gate of the element 13 of the transfer-in gate nearest the minor loop 1 are parallel.

These elements 4 and 13 are arranged in proximity to each other in order to ensure the propagation of the magnetic bubble. Magnetic poles caused to arise on the permalloy elements 4 and 13 by the rotating magnetic field interfere with each other, with the result that, especially when the bias magnetic field is large, a magnetic bubble propagated to the parts 4,14 is prone to be annihilated orto come out of the designed propagaton path. For this reason, the permitted upper limit of the bias magnetic field is kept low, and the propagation margin is reduced.

It is accordingly an object of this invention to provide a transfer-in gate of a magnetic bubble device which has a wide propagation margin for the bias field.

According to the invention, there is provided a magnetic bubble device comprising a minor loop for storing a magnetic bubble, a write major line which is disposed adjacent one end of said minor loop, and a transfer-in gate which is disposed between said minor loop and said write major line and which functions to transfer the magnetic bubble on said write major line into said minor loop, opposing surfaces of respectively (a) an element of said minor loop nearest said transfer-in gate and (b) an element of said transfer-in gate nearest said minor loop being inclined to each other.

With this construction, magnetic poles arising on the opposed parts on account of the rotating field interfere with each other only slightly. Even when the bias field is large, a magnetic bubble can reliably be propagated on a normal propagation path without being annihilated or coming out of the propagation path.

As a result, the propagation margin of the transferin gate of a magnetic bubble device according to this invention may be approximately double that of the prior-arttransfer-in gate.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic plan view of the transfer-in gate in a prior-art magnetic bubble device already described, Figure 2 is a schematic plan view of a transfer-in gate in a magnetic bubble device embodying this invention, Figure 3 is a graph showing the relationship between the angle of inclination a in Figure 2 and the propagation margin of bias fields, and Figures 4A and 4B are sketches of permalloy elements useful in the transfer-in gate in other embodiments of the invention.

Figure 2 shows the permalloy element of the transfer-in gate nearest a minor loop 22. Permalloy elements 17,18,19 which constitute part of the minor loop 22, the element 18 being nearest the transfer-in gate. The elements 16,17, 18 and 19 of Figure 2 respectively correspond generally to the elements 13,5,4 and 3 of Figure 1.

As previously, a magnetic bubble generated by a magnetic bubble generator (not shown) is propagated on a write major line (not shown) and arrives at the transfer-in gate. If at this moment current is caused to flow through a conductor loop (not shown) the magnetic bubble leaves the write major line and is propagated in a direction indicated by arrow 20 via the element 16 to the permalloy element 19 of the minor loop 22. Thereafter, the magnetic bubble is successively propagated to the elements of the minor loop 22 in accordance with the rotating field.

There are two points of difference between the transfer-in gate of Figure 1 and that of Figure 2. One is that in Figure 1 the upper and lower patterns constituting the minor loop are symmetrically opposed to each other across the center line, whereas in Figure 2 they are asymmetrically opposed across the center line being staggered by a half distance unit from each other. Because of this stagger construction, the packing density per unit area can be increased. This stagger construction is disclosed in U.S. Patent 4,007,447.

The other point of difference is the shapes of the permalloy elements 4,13 in Figure 1 and the permalloy elements 18, 16 in Figure 2. In Figure 1 the opposing surfaces B and C respectively of the arms of the element 4 (i.e. the surface facing the transferin gate) and the arm of the element 13 (i.e. the surface facing the minor loop 1) are parallel. In contrast, in the transfer-in gate embodying this invention of Figure 2, the opposing surfaces D and E respectively of the arm 23 of the element 18 facing the transfer-in gate and the arm 24 of the element 16 facing the minor loop 22 are inclined relative to each other, i.e. are relatively slanting at an angle of inclination a. For this reason explained above, this enables the propagation margin of bias fields to be enhanced.

Figure 3 shows the percentage variation of the propagation margin obtained when the angle of inclination a was varied using the permalloy ele me,-,.s sfshown in Figure 2 and setting the pattern spacing of the permalloy elements at 8 um, the intensity of the rotating field at 55 Oe and the frequency of the rotating field at 100 kHz. Figure 3 shows that the propagation margin at first increases with increase of the angle a, but it does not increase much further when a exceeds 300 and begins to decrease when a exceeds 900. The reason for this is thought to be that the propagation of the magnetic bubble between the permalloy elements is difficult when a exceeds 900.The permissible lower limit of the bias field hardly depends at all upon the value of a, so that the increase of the propagation margin illustrated in Figure 3 is mostly obtained by the rise of the allowable upper limit of the bias field. It is apparent from Figure 3 that a is advantageously within the range 300 to 900.

It has been experimentally confirmed that the shape of the fore end of the arm 24 of the permalloy element 16 has no effect on the increase or decrease of the propagation margin.

Needless to say, the shape of the element 16 nearest the minor loop 22 is not restricted to that shown in Figure 2. When the angle a is large, the element 16 may well be in a shape as shown in Figure 4A (a = 90 ). When a is not so large, the shape shown in Figure 4B may be used, in which the arm near the minor loop 22 resembles that the element 16 in Figure 2 (a = 300), while its arm remote from the minor loop 22 resembles that of the element in Figure 4A.

Claims (3)

1. A magnetic bubble device comprising a minor loop for storing a magnetic bubble, a write major line which is disposed adjacent one end of said minor cop, and a transfer-in gate which is disposed between said minor loop and said write major line and which functions to transfer the magnetic bubble on said write major line into said minor loop, opposing surfaces of respectively (a) an element of said minor loop nearest said transfer-in gate and (b) an element of said transfer-in gate nearest said minor loop being inclined to each other.

2. A magnetic bubble device according to claim 1 wherein the angle of inclination between said opposing surfaces is in the range 300 to 900.

3. A magnetic bubble device substantially as herein described with reference to and as shown in Figure 2 of the accompanying drawings or such a device modified as shown in Figure 4A or Figure 4B of the accompanying drawings.