JPS58223074A - Testing of demagnetization - Google Patents

Abstract

PURPOSE:To reduce variation in measured values while shorting the testing time by use of a bias magnetic field setting value in which about half of all minor loop numbers are poor in the operation as such. CONSTITUTION:A bias magnetic field is set at a point P higher than the upper limit of an estimated margin curve and then, demagnetization is done gradually from this point P. At the point P, all figures on a minor loop are poor in the operation and at the point Q on the curve B, almost all figures of the minor loop operates stably excluding specific rejected loops. In the method according to this method, the point R at which about half of all minor loop figures are poor in the operation is found between the points P and Q and the bias magnetic field value given here is made the demagnetization setting point. This point R is relatively stable as set point as it never depends on the number of pages with which the minor loop and less on a rejected loop. This enables the writing and reading of several pages in the sequence of a bubble writing and reading thereby shortening the testing time.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a testing method for a magnetic bubble memory used as a storage device for a Seiko computing device or its terminal.

(2) Background of the technology Magnetic bubble memory has numerous features such as non-volatility, high storage density, low power consumption, small size and light weight, and is also extremely popular because it is a solid-state device that does not contain any mechanical elements. It has high reliability and is expected to have a promising future as a large capacity memory. This magnetic bubble memory utilizes the fact that magnetic bubbles can be freely moved within a magnetic thin film having uniaxial anisotropy by a magnetic field.As shown in FIG. Rotating magnetic field generating coil 212 for driving < bias magnetic field generating magnets 3, 3', etc. for stably holding the bubble, etc.! It is composed of two.

The memory element 1 is made by forming a thin film of magnetic garnet on a gadolinium-gallium-garnet single-crystal substrate by liquid phase epitaxial growth, for example, and then forming a permalloy thin film on top of the half-disk as shown in Figure 2. A bubble transfer path is formed by arranging i9 turns such as The configuration of this no-pull transfer path includes a serial loop configuration and a major-minor configuration. FIG. 3 is a diagram showing an example of a major/minor configuration, and shows a major line 5 for writing having a pull generator 4, a major line 7 for reading having a nog pull detector 6, and A plurality of minor loops 1o9. ~10-n.

In such a magnetic bubble memory element, variations in conditions during the manufacturing process lead to variations in characteristic values. For this reason, since it is necessary to adjust the magnetization strength of the permanent magnet for applying the bias magnetic field, it is necessary to investigate the characteristics of the element before commercializing it.

(3) Prior Art and Problems FIG. 4 is a diagram showing the noise magnetic field margin, which is a typical characteristic of a magnetic bubble memory element. In the same figure,
The driving magnetic field is plotted on the horizontal axis, and the bias magnetic field is plotted on the vertical axis, and characteristic values are shown by curve A.

Note that the hatched area is the range in which stable operation occurs.

Conventionally, the lower limit of the bias magnetic field margin shown in FIG. 4 has been used as a setting point when determining the magnetic field value of the bias magnetic field applying magnet. However, this method has a disadvantage in that it causes deviations in the bias magnetic field value setting because there are large variations depending on the number of bubbles packed into the minor loop and dirt-related characteristics. (4) Purpose of the Invention The present invention In view of the drawbacks of the conventional art, it is an object of the present invention to provide a demagnetization test method that can measure the bias magnetic field setting of a magnetic bubble memory element in a short time and with little variation.

(5) According to the present invention, the purpose of the present invention is to reduce the bias magnetic field value of the magnetic bubble memo IJ A demagnetization test method for measuring the stable operating range of an element while subjecting the device to a demagnetization test method, the demagnetization test method is characterized in that the demagnetization set point is a magnetic field value at which the number of malfunctioning loops is equal to the total number of minor loops. This is achieved by providing

(6) 5 #5 Bright example Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 5 is a diagram for explaining the demagnetization test method according to the present invention. In the figure, the horizontal axis represents the driving magnetic field, and the vertical axis represents the bias magnetic field, and curve B is the expected bias magnetic field margin curve of a certain magnetic puzzle memory element.

The method of the present invention takes a bias (one threshold value) at a point P that is higher than the upper limit of this predicted margin curve, and gradually demagnetizes from this point P. In this case, a minor loop occurs at point P. All of the minor loops are malfunctioning, and at point Q on song #B, almost all of the minor loops except for a specific malfunctioning loop operate stably. However, in the method of the present invention, the points P and Q The point R at which all the fishing machines with minor loops are malfunctioning is found between them, and the bias magnetic field value at this time is set as the demagnetization setting point.

This point R is stable as a setting point because it does not depend on the number of pages packed into the minor loop and is less dependent on a specific defective loop, and the puzzle ride read sequence is possible with a ride read of several pages, so it can be tested. It also takes less time.

(7) Effects of the invention As explained in detail above, the demagnetization test method of the present invention has the following effects:
By using the bias magnetic field setting value at which the hook rods of all the minor loops are malfunctioning, there is a great effect that the variation in measured values is small and the test time can be shortened compared to the conventional method. .

[Brief explanation of drawings]

Figure 1 is a diagram for explaining a conventional magnetic bubble memory device, Figure 2 is a diagram for explaining a bubble transfer path of a magnetic bubble memory element, and Figure 3 is a diagram for explaining a conventional magnetic bubble memory element with a major-minor configuration. 4th diagram to explain
This figure shows the bias magnetic field margin characteristics of the magnetic bubble memory element, and FIG. 5 is a diagram for explaining the demagnetization test method according to the present invention. In the drawing, 4 is a bubble generator, 5 is a major line for writing, 6 is a bubble detector, 7 is a major line for reading, 8 is a transfer r-, 9 is a replicate dirt, and 10-1 to 10- are minor Each loop is shown. Patent Applicant Fujitsu Limited Patent Application Agent Akira Yoiki Patent Attorney Kazuyuki Nishidate Patent Attorney 1) Yukio Patent Attorney Akira Yamaguchi Figure 2

Claims (1)

[Claims] 1. Regarding a magnetic bubble memory element with a major-minor configuration, in a demagnetization test method that measures the stable operating range of the element while lowering the bias magnetic field value from a point higher than the upper limit of the expected bias magnetic field merging characteristic, the operation A demagnetization test method characterized in that the demagnetization setting point is a magnetic field value at which the number of defective loops is approximately equal to the total number of minor loops.