JPH06103591B2 - Magnetic bubble memory device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bubble memory device, and more particularly to improving the output of a magnetic bubble detector in a chip of the device.

[Background of the Invention]

The magnetic bubble memory device is a liquid phase epitaxial growth of a magnetic garnet single crystal on a non-magnetic garnet GGG substrate.
A conductor pattern such as a magnetic bubble generator made of Au / Mo and a divider is formed on this, and a magnetic balm transfer path made of a soft magnetic material such as Permalloy is further formed on the conductor pattern,
It forms the detector.

In recent years, as the density of magnetic bubble memory devices has increased, the cell pattern on the transfer path has tended to become smaller. If the cell pattern of the transfer path is miniaturized in this way, a large rotating magnetic field is required to transfer the magnetic bubbles. It cannot be increased. Therefore, by applying a bias magnetic field to the chip in one direction, the magnetic bubble transfer characteristic and the start / stop characteristic are improved even in a high-density element.

In general, a detector that detects the presence or absence of a magnetic bubble and converts it into an electric signal detects the magnetic bubble by utilizing the magnetoresistive effect. This detector is, as shown in FIG. 1, a magnifier 1 for gradually expanding a magnetic bubble in a string shape, and a detector line for detecting the presence or absence of a magnetic bubble by the passage of the magnetic bubble expanded to several mm. 2. Dummy detector line 3 etc. A current is made to flow through this detector line, the change in the magnetic resistance value due to the passage of bubbles is converted into a voltage, and the presence or absence of magnetic bubbles, that is, "1", "0" is detected. Note that P is the transfer direction of the magnetic bubble,
H _R is a rotating magnetic field, and H _B is a bias magnetic field.

FIG. 2 is a block diagram of a conventional chip using such a detector. Reference numeral 4 is the detector shown in FIG. 1, 5 is a minor loop for storing information, 6 is a lead track, and H _DC is a bias magnetic field. The bias magnetic field H _DC is applied in the chip plane in the replicator direction, that is, in the direction toward the lead track 6 of the minor loop 5 in order to transfer the magnetic bubbles of the minor loop 5 and improve the start / stop characteristics. Therefore, this direction is the direction in which the rotating magnetic field H _R advances 270 ° with respect to the magnetic bubble transfer direction P of the detector 4.

The signal detected by such a detector 4 is shown in FIG.
FIG. 3A is a waveform diagram of the voltage applied to the X coil for the rotating magnetic field, and the magnetic bubble transfer direction is set to 0 °.

The angle of the X-coil waveform expressed in (a) of FIG.
It is a value corresponding to the angle (phase) indicating the direction of the rotating magnetic field H _{R in} FIG. 4 or FIG.

FIG. 3B is a waveform diagram of the detection signal showing the drive voltage and the phase in comparison. 7 is the N output when there is no magnetic bubble, and 8 is the S output when there is a magnetic bubble. It is the peak portion 8a of the S output 8 that actually detects "1" or "0" of the magnetic bubble, but when the rotating magnetic field H _R becomes small, noise 7a is generated at this portion in the case of the N output 7. As will be described later with reference to FIG. 4, since this noise 7a is generated immediately after the phase of the peak portion 8a of the S output 8, the detection efficiency S / N of the magnetic bubble is remarkably lowered.

The noise 7a of the N output 7 increases as the rotating magnetic field H _R becomes smaller, and is generated in a phase in which the rotating magnetic field H _R rotates several tens of degrees from the magnetic bubble transfer direction (0 °).

That is, as shown in FIG. 4, noise is generated in the direction of the rotating magnetic field H _R1 which substantially coincides with the longitudinal direction of the serpentine pattern of the detector line 2.

It should be noted that the direction of the rotating magnetic field and the transfer position of the string-like bubbles are set to the fourth
In the figure, the angled arrow represents the transfer position of the bubble. The entrance side at 180 °, the central part at 270 °, 360
It is transferred to the exit side at 0 (0).

Here, the N output 7 is obtained by converting the difference in resistance value between the detector line 2 and the dummy detector line 3 shown in FIG. 1 into a voltage. In this case, if the magnetic resistance values of both lines are exactly the same, the N output 7 will always be 0 mV, but in reality the rotating magnetic field H _R
As a result, the magnetic domain state of the detector line constantly changes, and therefore fluctuates within a range of about ± 1.0 mV. In particular, in the phase of the rotating magnetic field H _R1 shown in FIG. 4, it becomes the timing at which the magnetization switches, and when H _R1 is sufficiently large, as shown in FIG.
The serpentine pattern is magnetized from ead to tail), but when H _R1 is small, this head-to-tail regular magnetization state is partially collapsed. As a result, the magnetic resistance values of the detector line 2 and the dummy detector line 3 become unbalanced and N
Noise 7a is generated at the output 7.

Next, the reason why noise occurs immediately after the peak phase will be described.

As explained in Fig. 4, noise causes H
_{When the} direction of _R1 is reached and the magnetization state of the detector switches as shown in the figure, the two detector lines 2 and 3 in FIG.
Caused by variations in the switching timing.

On the other hand, the magnetic bubble expanded like a string is transferred to the exit side of the detector in the H _R1 direction. On the detector line 2, the direction of the stray magnetic field generated by the magnetic bubble is
It is the same direction as H _R1 and acts in the direction of strengthening the size of H _R1 .

As a result, the switching of the detector line 2 occurs earlier than the dummy detector 3 when the magnetic bubble is on the detection line. This switching phase difference appears as the output of 8a in FIG. 3 (b). Therefore, the peak phase of the output 8a appears earlier than the phase of the noise 7a. That is, noise appears later than the peak phase, as shown in FIG.

As described above, the conventional magnetic bubble memory device has a drawback that the detection efficiency S / N of the magnetic bubble in the detector is significantly reduced.

[Object of the Invention]

The present invention has been made to solve the above-mentioned conventional drawbacks, and an object of the present invention is to provide a magnetic bubble memory device with reduced noise generated in the N output and high detection efficiency. .

[Outline of Invention]

In order to achieve such an object, the present invention sets the bias magnetic field direction to a predetermined direction with the magnetic bubble detector as a reference.

Example of Invention

Hereinafter, the present invention will be described in detail with reference to Examples. FIG. 5 is a characteristic diagram in which the horizontal axis represents the direction of the bias magnetic field H _DC with the magnetic bubble transfer direction in the detector being 0 °, and the vertical axis represents the PP peak value (mV) of N output noise. As you can see from the figure,
The noise of N output is the largest in the case where there is a bias magnetic field in the direction in which the rotating magnetic field advances 270 ° from the conventional magnetic bubble transfer direction as shown in FIG. However, in the range of A where the bias magnetic field direction is 0 ° to 90 °, the noise of N output becomes very small. Therefore, in the present invention, the rotating magnetic field is set in a direction advanced by 0 ° to 90 ° from the magnetic bubble transfer direction in the detector.

FIG. 6 is a block diagram of an embodiment of the magnetic bubble memory device according to the present invention. The bias magnetic field H _DC is 90 ° ahead of the phase of the rotating magnetic field H _R with respect to the magnetic bubble transfer direction P in the detector 4a. As a result, N output noise is 1m
It became below V.

Further, it is needless to say that it is effective for the magnetic bubble transfer timing in the detector because the bias magnetic field is applied in the magnetic bubble transfer direction of the detector or in the direction advantageous for the gap transfer of the stretcher pattern and the detector line. Nor.

Although the bias magnetic field direction with respect to the magnetic bubble transfer direction is set to 90 ° in the embodiment, it may be set to 0 ° or 0 ° and 90 °.
Any angle between ° may be used.

〔The invention's effect〕

As described above, according to the magnetic bubble memory device of the present invention, N output noise, that is, switching noise can be significantly reduced, and the detection efficiency S / N can be improved.

[Brief description of drawings]

1 is a block diagram of a magnetic bubble detector, FIG. 2 is a block diagram of a conventional magnetic bubble memory device, FIG. 3 is a waveform diagram of detection output, FIG. 4 is an explanatory diagram of a magnetization state of a detector line, and FIG. FIG. 5 is a characteristic diagram showing the relationship between the bias magnetic field direction and N output noise, and FIG. 6 is a configuration diagram of an embodiment of the magnetic bubble memory device according to the present invention. 1 ... Expander, 2 ... Detector line, 3 ... Dummy detector line, 4, 4a ... Detector, 5 ... Minor loop, 6 ...
... lead track, 7 ... N output, 7a ... noise, 8 ...
… S output, 8a …… Peak part, H _R …… Rotating magnetic field, H _B ……
Bias magnetic field, H _DC ... bias magnetic field, P ... detector magnetic bubble transfer direction.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Yanai 3300 Hayano, Mobara-shi, Chiba Hitachi Ltd. Mobara factory (56) References JP-A-58-35787 (JP, A)

Claims (1)

[Claims] 1. A magnetic bubble memory device having a magnetic bubble detector consisting of a detector line and an expander, wherein the in-plane bias magnetic field direction is 90 ° with respect to the magnetic bubble transfer direction of the magnetic bubble detector. A magnetic bubble memory device, characterized in that it is set in a direction of advanced phase, and the bias magnetic field direction is the same as the magnetic bubble transfer direction of the minor loop.