JPS6040109B2 - Current stretch bubble detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a magnetic bubble detection method in a magnetic bubble detector for a magnetic bubble memory device.

Recently, magnetic bubble memory devices that utilize magnetic bubbles are also required to increase their storage density, so one method that has been developed is to form a transfer pattern using ion implantation, which allows for higher density.

The details of the present invention will be explained below by taking an ion implantation device as an example. This method uses gadolinium gallium garnet (
GGG) A thin film 2 of magnetic garnet is formed on a substrate 1 by liquid phase epitaxial growth, and ions of hydrogen, neon, helium, etc. are implanted into a portion 4 of the magnetic thin film 2 other than the pattern 3. In the device in which the pattern 3 is formed in this way, the direction of the easy axis of magnetization of the ion-implanted portion 4 coincides with the in-plane direction as shown by arrow a, and the direction of the easy axis of magnetization of the patterned portion 3 is as shown by arrow b. It is perpendicular to the original in-plane direction. Therefore, the bubble 5 is transferred along the periphery of the pattern 3 as shown by the arrow c by the rotating magnetic field. This pattern 3 has a shape in which circular patterns are overlapped and connected one by one, and unlike conventional permalloy patterns, it does not require gaps, so the dimensional accuracy does not need to be loose. will be realized. In such an ion-implanted magnetic bubble memory element, a conventional stretch detector using a permalloy pattern is not used to detect bubbles, so a detector using a stretch conductor as shown in FIG. 3 is used. Reference numeral 6 in the figure is a transfer pattern, 7 is a stretch conductor, and 8
is a permalloid detector that uses magnetoresistive effect. To explain the operation of this detector, the bubble 9 is exposed to a rotating magnetic field H
r, the bubble is transferred from left to right in the transfer pattern 6 as shown by the arrow, but while the bubble is staying at the cusp 10 located at the hairpin loop of the stretch conductor 7, a stretch pulse current is applied to the stretch conductor 7 and the bubble is is enlarged to form a stripe domain, and the change in resistance of the permalloid detector 8 due to this stripe domain is detected. In this case, the conventional detection method used was to stretch the bubble during one cycle of the rotating magnetic field and then erase or return it to a bubble, but this method has the disadvantage that when driven at high speeds, there is not enough time to stretch the bubble. However, there was a drawback that the detection voltage decreased due to the relationship between the direction of the detector and the driving magnetic field. For this reason, one method is to apply the stretch pulse 11 as shown in Fig. 4 during two cycles of the rotating magnetic field, taking advantage of the fact that bubbles with a major-minor configuration are generated once every two cycles of the rotating magnetic field. and stretch the bubble,
A detection method has been proposed in which the distortion pulse 12 is then applied to erase or restore the bubble. This method does not compensate for the drawbacks of the former and increases the detection voltage, but the pulse width and current value of the stretch current affect the bubble of the bit in front of the transfer pattern where the detector is located, causing the upper limit of the bias margin to increase. The disadvantage is that it varies significantly. The present invention has been devised to remedy this drawback. Therefore, in the present invention, in a bubble detection method for a detector equipped with a stretch conductor of an ion-implanted magnetic bubble memory device, the stretch current applied to the stretch conductor is a pedestal pulse current.

The method of the present invention will be explained in detail below based on the accompanying drawings.

FIG. 5 shows the waveform of a pulse used in the current stretch bubble detection method of the present invention.

The reference numeral 13 in the figure is a stretch/gust, and the reference numeral 14 is a destretch/finger. The stretch pulse 13 has a current of 1,
A pedestal pulse of current 12 is added to the main pulse of . Further, the destretch bubble 13 has the same shape as the conventional one. The method of the invention applies such pulses to the stretch conductor of the detector. Figure 6 is a diagram that examines the influence of the main pulse position on the current margin when the stretching pulse point is kept constant at -110° of the rotating magnetic field.The vertical axis represents the main pulse current, and the horizontal axis represents the field field. The angle of the magnetic field (the reference is the direction when the bubble is at the cusp of the transfer pattern is oo).

) and the relationship between the two is shown by curve A. In addition, the total pulse width of this pulse is 2 mm S, the width of the main pulse is 0.4 mm S,
The current value of the pedestal was 3 hA. The figure shows that it is better to position the main pulse in front of the pedestal. Therefore, in the following, the main pulse is set in front of the pedestal. Figures 7 and 8
The figure shows the phase (0
)-current characteristic diagram and current-bias characteristic diagram. In Fig. 7, the vertical axis represents the current of the main pulse, and the horizontal axis represents the rotating magnetic field angle, and curve B indicates that the width of the main pulse is 0. 2u
Curve C shows the case where the main pulse width is 0.4 rS, and curve D shows the case where the main pulse width is 0.8 rS.

Note that the current value of these pedestals was 3 skin A. For comparison, the case of a conventional rectangular pulse with a width of 20.0 peaks S is shown by a curve E. In FIG. 8, the vertical axis represents the bias magnetic field, the axis represents the current value of the main pulse, and the width of the main pulse is 0.2, 0.
The cases of 4 and 0.8 rS are shown by curves F, G and 1, respectively, and for comparison, the case of a conventional rectangular pulse with a width of 0.21 S is shown by curve K. In addition, the current value of the pedestal in this case is 3
The enemy was hA. From both figures, it can be seen that the pedestal pulse of the present invention has a larger current margin than the subordinate rectangular pulse, and the upper limit of the bias margin is significantly improved. FIG. 9 shows the phase (8)-detection voltage characteristics of the secondary rectangular pulse and the pedestal pulse of the present invention, where the total pulse width of the present invention is 2 peaks S and the main pulse width is 0.4 mm The case where the main pulse current is 7 A and the pedestal current is 3 hA is shown by curve L, and the case where the conventional rectangular pulse width is 2 peaks S and the current is 55 mA is shown by curve M.

As shown in the figure, the detection voltages are almost the same in both cases, and even if the pulse waveform according to the present invention is used, a large detection voltage and detection efficiency can be obtained with high-speed driving. As explained above using an ion-implanted bubble device as an example, the method of the present invention improves the current margin and bias margin by making the stretching current applied to the detector equipped with the stretch conductor of the magnetic bubble memory device into a pedestal pulse. This contributes to improving the reliability of bubble detection in magnetic bubble memory devices.

[Brief explanation of drawings]

FIG. 1 is a plan view of a magnetic bubble memory element formed by ion implantation, FIG. 2 is a sectional view taken along the Rolo line in FIG. 1, FIG. 3 is a plan view of a bubble detector having a stretch conductor, and FIG. The figure is a waveform diagram showing the slave pulse waveform applied to the bubble detector, FIG. 5 is a waveform diagram showing the pulse waveform used in the current stretch bubble detection method according to the present invention, and FIG. Figures 7 and 8 are diagrams showing the influence of the position of the main pulse on the current margin; FIG. 9 is a phase-detection voltage characteristic diagram when a pedestal pulse and a subordinate rectangular pulse according to the present invention are used. 6... Transfer pattern, 7... Stretch conductor, 8... Permalloy detector, 9... Baffle, 10... Cusp, 11, 13... Stretch pulse, 12, 14... Destretch pulse. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 8 Figure 6 Figure 7 Figure 9

Claims (1)

[Claims] 1. A current stretch bubble detection method for a detector equipped with a stretch conductor of a magnetic bubble memory device, characterized in that the stretch current applied to the stretch conductor is a pedestal pulse current.