JPS6330717B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a bubble magnetic domain (hereinafter simply referred to as bubble).
Regarding elements.

Conventionally, bubble devices have adopted a method in which soft magnetic patterns are provided on a bubble retaining layer with a gap between them and bubbles are transferred by in-plane magnetic field rotation. However, the gaps in the pattern are undesirable from the viewpoint of reducing bubble density, impeding high-speed bubble transfer, and limiting pattern microfabrication.

On the other hand, US Pat. No. 3,828,329 provides an element that transfers bubbles using a gapless pattern, and its development has been rapidly progressing recently. There, the pattern is formed by ion implantation. Since the transfer pattern was in the form of a series of circles, devices developed subsequently that used patterns with no gaps were also called continuous disk (hereinafter referred to as CD) devices.

However, in addition to the above-mentioned pattern of connected circles, the transfer pattern of conventional CD elements includes several patterns such as a continuous diamond pattern as shown in U.S. Pat. No. 4,070,658. Although attempts have been made, it is not clear which is the preferred transfer pattern.
Furthermore, when the pattern period is reduced in order to further increase the bubble density in the future, it is becoming difficult to form patterns such as a series of circles due to the limitations of microfabrication. Specifically, the processing limit in current device processing is said to be approximately 1 μm. Therefore, it can be said that even a pattern with a period of 4 μm, a complicated pattern such as a series of circles is at the processing limit.

SUMMARY OF THE INVENTION An object of the present invention is to solve such difficulties in processing the transfer pattern of a conventional CD element and to provide a CD element having a pattern shape with improved transfer characteristics.

According to the present invention, in a CD bubble device in which the transfer pattern elements have a periodic transfer pattern with no gaps between them, by using a cross-shaped pattern whose length in the transfer direction matches the pattern period as the periodic transfer pattern element, A CD bubble element with easy pattern formation and good transfer characteristics can be obtained.

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

Example 1 FIG. 1 shows an example of a transfer pattern element of a bubble element of the present invention. The length of the pattern is the pattern period P. FIG. 2 shows a periodic pattern in which the cross-shaped pattern elements of FIG. 1 are arranged. In this embodiment, the depth a of the cusp portion 21 is set to approximately 1/4 times the pattern period P, and the bottom width 2b of the cusp portion 21 is set to approximately 1/2 times the pattern period. Pattern period P = 4μ
m, the cusp depth a is approximately 1 μm, and the cusp bottom width 2
b is approximately 2 μm, and this pattern is the current 1 μm
It can be formed sufficiently within the range of mask forming technology according to the rule. However, after the pattern is formed, the corners of the convex portions and concave portions of the pattern are slightly rounded as shown by broken lines 23 in FIG. 2, and the pattern shape of the present invention includes such rounded pattern shapes. 2
2 is the apex portion of the pattern.

FIG. 3 is a diagram showing the quasi-static simple transfer margin in a good loop, where the horizontal axis Hr represents the rotating magnetic field and the vertical axis Hz represents the bias magnetic field. The bubble retaining layer is conventionally grown on a Gd ₃ Ga ₅ O ₁₂ (111) single crystal substrate surface to a thickness of about 0.8 μm by liquid phase epitaxial (LPE) growth. The bubble retention layer is (SmLuBiCa) ₃ ((FeGe) ₅ O ₁₂ garnet with a stripe width of about 1.0 μm).

In this example, a different type of drive layer is grown by LPE in order to easily obtain an in-plane magnetization layer by ion implantation. The drive layer is (GdSmTmCa) ₃ (FeGe) ₅ O ₁₂ garnet and has a thickness of about 0.5 μm. The drive layer has a saturation magnetization 4πMd of about 590 Gauss and a Q value of about 1.7. A pattern mask is formed with AuCr on the drive layer, and
A transfer pattern was formed by implanting He ⁺ ions at 5×10 ¹⁵ /cm ² at 100 KeV.

The direction of the black circle around the circle in the lower left corner of FIG. 3 indicates the direction in which magnetization is difficult in the plane. A good loop is a loop formed parallel to this direction of difficult magnetization. Three loops each having a length of 21 bits are formed in parallel, and the measurement of the transfer margin shown in FIG. 3 was performed on the central loop.

Now, in FIG. 3, the solid line 31 indicates a loop (a) in the upper left corner of the present invention shown in FIG. 2, and the dotted line 32 indicates a loop consisting of a pattern of vertical ellipses. Regarding (b), the broken line 33 indicates the bubble transfer margin for each loop (c) consisting of a pattern of circles with a diameter of about 4 μm. As is clear from this result, the cross-shaped pattern of the present invention has a wider margin than a pattern consisting of a series of circles or vertical ellipses. In particular, the margin improvement is remarkable in a region where the in-plane magnetic field is relatively low. This is considered to be because errors that occur along circular or oval patterns as shown in b and c in FIG. 3 do not occur in the cross-shaped pattern of the present invention. That is, it is effective for transfer to form the cusp portion 21 by increasing the angle between the side from the cusp portion 21 toward the apex 22 and the transfer loop direction, and by ensuring the cusp bottom width 2b is greater than the processing limit, as in the present invention. It is thought that it is effective.

Figure 4 shows the track on the easy axis side of a loop in which the pattern in Figure 1 is arranged perpendicular to the axis of hard magnetization.
It shows the quasi-static simple transfer margin of bubbles on the so-called super track. As you can see, there is a sufficient margin, which is comparable to the margin of a pattern consisting of a series of circles.

Example 2 In Example 1, when the cusp bottom width 2b in Fig. 2 is kept constant at half the pattern period and only the cusp depth a is made deep to 0.3 times the pattern period P, the quasi-static simple transfer margin of the good loop is It was found that the margin of the supertrack is wider toward the lower in-plane magnetic field than the solid line 31 in FIG. 3, while the margin of the supertrack is narrower toward the lower in-plane magnetic field than in FIG.

Example 3 When the cusp depth a in Example 2 is made shallower to approximately 0.2 times the pattern period P, the quasi-static simple transfer margin of the good loop is reduced on the low in-plane magnetic field side compared to the solid line in Figure 3. Also, with Super Track, results were obtained that were almost the same as in Figure 4, or slightly better.

Example 4 In Example 1, when the cusp depth a is kept constant at approximately 0.25 times the pattern period P and the cusp bottom width 2b is selected to be approximately 1/3 of the pattern period P, the transfer margin of the good loop is as shown in FIG. Although it is slightly narrower than the solid line 31, it is almost the same.
It was almost the same as the figure.

Example 5 When the cusp bottom width 2b in Example 4 was selected to be about 2/3 of the pattern period, the good loop transfer margin was worse than the solid line 31 in Figure 3, but in the super track it was almost the same as in Figure 4. It was hot.

As explained above, according to the present invention, a transfer pattern with a short pattern period can be formed even with current technology with a processing accuracy of about 1 μm, compared to a pattern with a complicated shape such as a series of circles. It is possible to obtain a bubble transfer margin that is comparable to that of the conventional method, and its industrial significance is great.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a cross-shaped transfer pattern element in the present invention, FIG. 2 is a diagram showing a periodic pattern in which two cross-shaped pattern elements of FIG. FIG. 4 is a diagram showing the measurement results of the simple transfer margin, and FIG. 4 is a diagram showing the supertrack margin of a cross-shaped pattern with a period of 4 μm. In the figure, 21 is the cusp part of the pattern, 22
is the apex of the pattern, 23 is the rounded pattern of the present invention, P is the pattern period, a is the cusp depth 2b is the cusp bottom width, 31 is the transfer margin of the cross-shaped pattern of one embodiment of the present invention, 32 is the 33 represents the transfer margin of a pattern of vertical ellipses, and 33 represents the transfer margin of a pattern of circles.

Claims (1)

[Claims] 1. In a continuous disk bubble magnetic domain element having a periodic transfer pattern formed by interconnecting transfer pattern elements without gaps, the transfer pattern elements are a cross-shaped pattern whose length in the transfer direction matches the pattern period. A bubble magnetic domain element featuring: