JPS6020382A - Bubble detector for contiguous disk bubble element - Google Patents

Abstract

PURPOSE:To reduce magnetization switching noises and improve the reliability of a bubble detector by providing a ''Permalloy'' pattern near a ''Permalloy'' pattern for bubble detection in parallel. CONSTITUTION:A magnetic bubble of a magnetic bubble transfer path pattern 11 is detected through a ''Permalloy'' pattern 13 connected to a conductor pattern 12 for bubble expansion. Then, a ''Permalloy'' pattern 21 is provided near said pattern 13 in parallel, and the pattern 13 increases in pattern width practically to reduce a counter magnetic field. Therefore, magnetization switching noises are reduced to improve the reliability of a magnetic bubble detector.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a contiguous disc nopple element bubble detector.

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 above-mentioned pattern gaps are undesirable in terms of a decrease in pull density, an obstacle to high-speed bubble transfer, and a limit to pattern microfabrication.
U.S. Pat. No. 3,828,329 discloses a device that transfers bubbles using a gapless pattern, and its development has been progressing rapidly recently. There, the pattern is formed by ion implantation. Since the transfer pattern of the Mizuko had a shape of a series of circles, it is said to be a continuous disk (hereinafter abbreviated as CD) element, including those with shapes developed later.

In the CD element, the bubble detector is the most 7F,'';'l
Na++: is one of the details. CD element bubble detector ('', i Seira, permalloy pattern f for bubble detection
F. A method is used in which a bubble is expanded by a current magnetic field and the magnetic field is detected by the magnetoresistance effect of a permalloy pattern. FIG. 1 shows a conventional example.

In FIG. 1, the bubble IO is transferred along the pattern 11 formed by ion implantation, and then
elongated by the magnetic field of the pattern 12; Detection pattern 1 made of permalloy for the magnetic field of a bubble with an elongated length J
3, it is detected using magnetoresistive 7 hairs.

The non-ion implanted region pattern 14 is provided to facilitate detection of the magnetic field from the elongated bubble. In addition to the magnetic field from the elongated bubble, the magnetic field that causes the change in magnetoresistance of the detection pattern includes the in-plane rotational drive magnetic field ()l
There are magnetic fields from a) and the conductor pattern 12, but in order to subtract the contributions from these, a dummy detector is usually provided in addition to the active detector. The active detector and the dummy detector are usually made to have the same shape, but in reality, it is nearly impossible to reduce the magnetic resistance change due to contributions other than the bubble magnetic field to zero, and this appears as noise in the bubble detection signal. If this noise is large, it impairs the reliability of the bubble detector and is a problem in terms of device operation.

Noise, which is a problem with conventional detectors, is the problem in IE Transactions on Fist Magnetic,
As described in Vol. (1980), page 99, this is magnetization switching noise of Permalloy, and this noise becomes more noticeable as the Permalloy pattern width becomes narrower. The phenomenon in which noise increases in the magnetoresistive signal as the permalloy pattern width becomes narrower is explained by the fact that the demagnetizing field of the permalloy pattern increases, making it easier to generate magnetic domains. The permalloy pattern width is usually determined to be 1 to 2 times the bubble diameter so as to maximize the signal output by the bubble magnetic field. If the permalloy pattern width is made larger than usual in order to reduce the magnetization switching noise described above, the problem is that the signal output decreases and the shear ratio is not improved. Currently, puzzle diameters are becoming smaller in order to increase the capacity of memory, but the permalloy detection pattern width also decreases, so the problem of permalloy magnetization switching noise tends to increase.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable CD bubble detector that compensates for the drawbacks regarding magnetization switching noise of conventional CD bubble detectors using the magnetoresistive effect of permalloy.

That is, the present invention adds another permalloy pattern in addition to the permalloy pattern for bubble detection in a CD element bubble detector in which a permalloy pattern for bubble detection is provided on the bubble retaining layer, and furthermore, this invention is used for bubble detection. This is a CD element bubble detector characterized in that it is provided in parallel in the vicinity of a permalloy pattern.

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

FIG. 2 is a schematic diagram showing a first embodiment of the bubble detector of the present invention. The bubble transfer path 11, the conductor pattern 12 for puzzle extension, the non-ion implantation pattern 14, and the permalloy pattern 13 for bubble detection are almost the same as the conventional ones, but the new permalloy pattern 21 is parallel to both sides of the bubble detection pattern 13. It is arranged as follows. 1μm bubble C
The thickness of the permalloy pattern 13 of the D element is 300 mm.
A. The pattern width is approximately 1.5 μm. The film thickness and pattern width of the permalloy pattern 21 are the same as those of the pattern 13.The pattern shown in FIG. 2 can be formed by simply changing the mask compared to the conventional type. Detection No. Malloy width approx. 1
．． For the 5 μm conventional detector, permalloy magnetization switching noise is observed, especially in the in-plane rotating magnetic field I (B500
There were many problems near en. On the other hand, in the case of the detector shown in FIG. 2, the conventional noise is hardly seen. In general, the magnitude of the demagnetizing field of a permalloy pattern with pattern width WS film thickness t and saturation a magnetic WM is approximately 4πM
It is expressed as t/W, and in the case of FIG. 2, it is considered that by arranging the permalloy patterns close to each other, the pattern width effectively increases and the demagnetizing field decreases. That is, it is interpreted that magnetic domains are less likely to be formed, and the magnetization of permalloy rotates easily with a lower in-plane rotating magnetic field than in the conventional type, resulting in less noise in the magnetoresistive signal. In addition, in this embodiment, the conductor current value for bubble expansion is reduced compared to the conventional one, and by arranging more permalloy patterns 21, the expansion current value is somewhat reduced, which has the advantage of lowering the duty of the detector. discovered. This is thought to be because the interaction between the permalloy pattern and the bubbles makes it easier for the bubbles to strip out.

FIG. 3 is a schematic diagram showing a second embodiment of the bubble detector of the present invention. This embodiment is characterized in that another permalloy pattern 31 is provided parallel to the bent permalloy pattern for bubble detection. The detector with a bent permalloy pattern for bubble detection can maintain the same output even if the length of the bubble elongated conductor is halved compared to the conventional normal type, reducing the elongated pulse and reducing donor resistance. It has the advantage of lower duty compared to conventional conventional types. Regarding permalloy magnetization switching noise, it was still observed, although it was less than the conventional type. On the other hand, by adding another permalloy pattern 31 in addition to the detection permalloy pattern 13 as shown in FIG. 3, the permalloy magnetization switching noise can hardly be seen. In addition, in FIG. 3, noise reduction was observed even when the permalloy pattern 31 was divided and arranged at the bent portion as shown in FIG. 8g2.

As explained above, according to the present invention, the permalloy magnetization switching noise of the detector can be reduced compared to the conventional CD element bubble detector by simply changing the mask, and the bubble extension current can also be reduced. There is also an advantage in terms of density, which has the effect of increasing the capacity of a highly reliable bubble element.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a conventional CD element bubble detector;
FIG. 2 is a schematic diagram showing a first embodiment of the invention, and FIG. 3 is a schematic diagram showing a second embodiment of the invention. 0...bubble, 11...bubble transfer path pattern,
12... Conductor pattern, 13... Permalloy pattern for bubble detection, 14... Non-ion implanted region pattern, 21... Permalloy pattern, 31... Permalloy pattern. Patent applicant: NEC Corporation

Claims (1)

[Claims] (1) In a bubble detector of a contiguous disk bubble element in which a No-Malloy pattern for bubble detection is provided on a bubble holding layer, another permalloy pattern is provided in parallel in the vicinity of the permalloy pattern for bubble detection. A bubble detector using a continuous disk bubble element.