JPH04295689A - Detection method of magnetic bubble - Google Patents

Abstract

PURPOSE:To separate a magnetic-bubble detection signal from a noise and to quickly slip a magnetic bubble element out of a dead zone by exerting a revolving magnetic field provided with a DC component in a required direction. CONSTITUTION:Magnetic bubbles are moved forcibly by using a revolving magnetic field; the bit pattern of the magnetic bubbles is detected by using a stretcher S and a magnetic-field detection element 2. When a bias magnetic field HB is directed toward the surface from the rear, the revolving magnetic field provided with the following is exerted on the magnetic bubbles: a DC component in a direction in which the element 2 is arranged inside the stretcher G out of sensitivity directions of the element 2; and a DC component in a direction perpendicular to the sensitivity directions of the element 2 by being turned by 90 deg. to a direction opposite to the revolving magnetic field inside the face of the element 2 from the direction. When the magnetic field HB is in the opposite direction, the revolving magnetic field provided with the DC component in the same opposite direction is exerted. Then, a magnetic-bubble detection signal and a switching noise which is generated by the element 2 are separated in terms of their timing, the magnetic bubble element is slipped quickly out of a dead zone and a wide-range detection can be performed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bubble detection method, and more particularly to a magnetic bubble detection method that separates a magnetic bubble detection signal from noise and obtains a stable and wide magnetic bubble detection signal.

0002

2. Description of the Related Art The principle of a rotational speed detector using magnetic bubbles is widely known, and will be briefly explained here. Figure 31
Figure 3 is a diagram of the operating principle of a rotation speed detector using magnetic bubbles.
2 is a pattern diagram of the transfer element loop formed on the magnetic bubble element of FIG. 31, and FIG. 33 is an enlarged view of the stretcher portion of the transfer element loop of FIG. 32.

In FIG. 31, a magnetic bubble element 1 is made of a material that generates magnetic bubbles. To explain,
A magnetic bubble is generated in a cylindrical shape in a perpendicularly magnetized film epitaxially grown to a thickness of several μm on GGG (gadolinium-gallium-garnet) by applying a perpendicular magnetic field of appropriate strength. This magnetic bubble element 1 includes magnetic bubble detection elements 12 and 13, an aluminum wiring pattern 14,
15 and 16 are formed (see FIG. 33). The magnetic bubble detection elements 12 and 13 are composed of magnetoresistive elements (for example, permalloy). Further, in the magnetic bubble element 1, a transfer element 11 made of a thin film of permalloy is formed in a loop shape, along which the magnetic bubble is transferred (Fig. 32
, see Figure 33). Although one transfer element loop is shown in FIG. 32, a plurality of transfer element loops are actually provided on the magnetic bubble element 1. Each transfer element loop has magnetic bubbles written in the bit pattern of the memory wheel. Note that the plane on which the magnetic bubble element 1 is arranged is called an xy plane for convenience.

A set of two bias magnets 2, 2' (Fig. 31
) has the effect of applying a constant perpendicular bias magnetic field to the magnetic bubble element 1 and holding a bubble-shaped magnetic domain. The readout coils 3 and 4 are arranged around the magnetic bubble element 1 as shown in FIG. The readout coils 3 and 4 are used to read out the cumulative number of rotations of the rotating shaft to which the ring magnet 5 is fixed.They generate a rotating magnetic field by passing an alternating current through them, and generate magnetic bubbles 17, 18, 19.
Transfer.

Ring magnet 5 is a permanent magnet attached to a rotating shaft (not shown). This ring magnet 5
gives a parallel in-plane magnetic field to the magnetic bubble element 1, and this in-plane magnetic field rotates as the rotating shaft rotates. The magnetic bubble circulates around the transfer element loop with one transfer element/one rotating magnetic field. FIG. 31 shows an example of a ring magnet magnetized with eight poles. In this case, when the rotating shaft rotates once, the magnetic bubble moves four transfer elements 11.

Each transfer element loop shown in FIG. 32 has magnetic bubbles written in a special arrangement pattern based on the "memory wheel principle." This special arrangement pattern is a pattern characterized in that a continuous bit pattern cut out from a certain position among all bit patterns is not the same as a pattern with the same number of bits cut out from another position. Therefore, by reading out a pattern of several consecutive bits from a certain fixed position, it is possible to know the rotational shift amount of the loop.

[0007] Magnetic bubbles are detected by the magnetic bubble detector 10 placed at the certain position. The magnetic bubble detector 10 is composed of magnetic bubble detection elements 12 and 13 shown in FIG. 33. The magnetic bubble detection elements 12 and 13 include
A constant current is previously passed through the aluminum wiring patterns 14, 15, and 16 (aluminum wiring pattern 16 is at ground potential). When the magnetic bubbles 17, 18, 19 move to the portions of the magnetic bubble detection elements 12, 13, this resistance value changes, so that the potentials of the aluminum wiring patterns 14, 15 change. A magnetic bubble detection signal is obtained by differentially calculating the potential signals of these two wiring patterns 14 and 15 using a differential amplifier (not shown).

In the magnetic bubble element 1 as described above,
On the transfer element loop, for example, a bit pattern of 8 bits per loop (
01110100) is formed depending on the presence or absence of magnetic bubbles. In the embodiment shown in FIG. 32, a larger number of bits (
For example, the number of bits is around 49 bits), but for the sake of clarity, 8 bits will be used for explanation here. When the ring magnet 5 rotates, this 8-bit bit pattern circulates on the transfer element loop in accordance with the rotation. This cyclic operation is shown in Figure 3.
The operation is performed normally even if the first device is in a power outage state.

For example, when the ring magnet 5 rotates 10 times while the power to the rotation speed detector shown in FIG. The magnetic bubbles in the pattern are moving. When the power is restored, in order to measure how many times the ring magnet has rotated, the reading coils 3 and 4 are operated to generate a rotating magnetic field, and the position of the magnetic bubble is sequentially moved by, for example, three transfer elements. Therefore, three time-series bit patterns are read out from the magnetic bubble detector 10, and from this pattern the cumulative number of rotations of the ring magnet 5 can be determined based on the "memory wheel principle". After the detection, the readout coils 3 and 4 apply a rotating magnetic field in the opposite direction to the above-described direction to the magnetic bubble element 1 to move the magnetic bubble by three transfer elements and return it to its original position.

[0010] In order to read the cumulative number of rotations of the rotating shaft, if the magnetic bubble is not returned to its original position, this will be added to the cumulative number of rotations of the rotating shaft, and the accurate cumulative number of rotations will be inaccurate. This is because it becomes impossible to measure.

Here, when the readout coils 3 and 4 are operated, the magnetic field HM generated by the readout coils 3 and 4 and the magnetic field HR generated by the ring magnet 5 are superimposed, and the magnetic bubble detection element 12 of the magnetic bubble element 1 is Added to 13. In a region where the vector direction of the magnetic field HR of the ring magnet 5 and the vector direction of the magnetic field HM of the readout coils 3 and 4 are oriented in the same direction, the magnetic bubble detection elements 12 and 13 made of permalloy are magnetically saturated. Magnetic bubble 17, 18
, 19 cannot be detected.

These will be explained with reference to FIG. 34 and FIG. In order to transfer the magnetic bubbles 17, 18, 19, it is necessary to apply an in-plane magnetic field of, for example, 40 Gauss or more. Assuming that the magnetic field HR generated by the ring magnet 5 is 40 Gauss, the rotation of the ring magnet 5 attached to the shaft results in a vector locus of a small circle in FIG. 34. When the ring magnet 5 stops at the angle of the vector OA and the cumulative number of rotations of the ring magnet 5 is measured by the readout coils 3 and 4, the rotating magnetic field by the readout coils 3 and 4 (for example, HM
=90 Gauss) becomes a great circle centered on point A (see FIG. 34). That is, when viewed from the origin 0, the vector sum OB changes between 50 and 130 Gauss.

On the other hand, the magnetic field-resistance value change characteristics of the magnetic bubble detection elements 12 and 13 are as shown in FIG. 35, and the resistance value change is saturated at about 60 Gauss. When arranged so that magnetic bubbles are detected when the vector sum is directed toward OC in FIG. 34, the magnetic bubbles 17, 18 are saturated due to the saturation of the magnetic bubble detection elements 12 and 13 (60 Gauss or more from FIG. 34).
, 19 cannot be detected.

[0014] In view of this point, the present applicant filed Utility Model Application No. 126991/1983 to solve this problem. This earlier application uses two Hall elements to measure the x and y components of the magnetic field HR generated by the ring magnet, and
The DC currents Hx offset and Hy offset that cancel out are superimposed on the readout coils 3 and 4. FIG. 36 shows the ring magnet 5 and Hall elements 20, 2 of this earlier application.
1 is a perspective view showing the positional relationship between the magnetic bubble element 1 and the magnetic bubble element 1. FIG. Here, the X-axis Hall element 20 measures the X-axis magnetic field (magnetic field generated by the ring magnet 5) component of the magnetic bubble element 1.
is arranged so as to coincide with the coordinate axis X direction, and the Y-axis Hall element 21 is arranged so as to coincide with the coordinate axis Y direction. Further, FIG. 37 is a configuration diagram showing a circuit configuration for generating DC current Hx offset and Hy offset. With this configuration, the magnetic field from the ring magnet on the magnetic bubble element is canceled by the direct current Hx offset and Hy offset.

The magnetic bubble is detected by the magnetic bubble detection elements 12 and 13, and a detection signal as shown in FIG. 38 is obtained. In this case, in order to easily read out the magnetic bubbles, it is necessary that the detection signal has a good S/N ratio and a wide detection signal width.

[0016]

However, as shown in FIG. 38, noise is superimposed on the detection signal. This noise is switching noise (called Barkhausen noise) generated by the magnetic bubble detection element itself, and cannot be eliminated. This Barkhausen noise is shown in Figure 39.
As shown in , when a magnetic field vibrating in the Hy direction, which should have no sensitivity originally, is applied, a constant Hy value is generated. In other words, the fall of the detection signal (Fig. 38) is accelerated,
It is this Barkhausen noise that worsens the S/N.

Furthermore, the Hx direction sensitivity curve of the magnetic bubble detection element has a dead zone as shown in FIG. 40 (same scale as FIG. 39). Therefore, a detection signal is not output unless the magnetic field in the Hx direction increases to a certain extent. It is this dead zone that delays the rise of the detection signal and narrows the detection signal width.

[0018] For the above reasons, in magnetic bubble readout using a rotating magnetic field symmetrical to the origin, when a disturbance magnetic field is applied, stable magnetic bubble readout cannot be performed due to deterioration of S/N, signal width phenomenon, etc. There was a case.

[0019] Conventionally, an offset magnetic field is applied by tilting a bias magnet, and this is canceled when reading magnetic bubbles.
Although proposals have been made in publications such as No. 1678,
It did not solve the above problems. That is, there is no regulation regarding the direction of offset.

The present invention has been made with attention to these points, and its purpose is to separate the magnetic bubble detection signal from the noise component, and to separate the signal processing at the subsequent stage. An object of the present invention is to provide a magnetic bubble detection method capable of obtaining a stable and wide magnetic bubble detection signal.

[0021]

[Means for Solving the Problems] The present invention, which solves the above problems, uses a stretcher and a thin film type magnetic bubble detection element using a magnetoresistive effect, and forces a magnetic bubble by generating a rotating magnetic field in a readout coil. In a magnetic bubble detection method in which the bit pattern of a magnetic bubble is detected by a magnetic bubble detection element, when a bias magnetic field is applied from the back side of the magnetic bubble element toward the front side, the stretcher in the sensitivity direction of the detection element The magnetic bubble is generated by rotating 90 degrees from this direction in the direction opposite to the rotating magnetic field for moving the magnetic bubble within the plane of the magnetic bubble detection element. A rotating magnetic field having a direct current component perpendicular to the sensitivity direction of the detection element is applied to the magnetic bubble element, and when the bias magnetic field is applied from the front surface to the back surface of the magnetic bubble element, the sensitivity direction of the detection element Among them, a DC component in the opposite direction to the direction in which the magnetic bubble detection element is arranged in the stretcher, and a rotating magnetic field for moving the magnetic bubble within the plane of the magnetic bubble detection element from the direction in which the detection element is arranged. A rotating magnetic field is applied to the magnetic bubble element by rotating 90 degrees in the direction of the magnetic bubble detection element and having a DC component perpendicular to the sensitivity direction of the magnetic bubble detection element.

[0022]

[Function] In the method of the present invention, it is possible to get out of the dead zone of the magnetic bubble detection element quickly, the detection signal rises quickly, and the width of the detection signal can be widened. In addition, the timing of noise added to the detection signal (switching noise generated by the magnetic bubble detection element itself) and the falling timing of the detection signal can be separated, and the S/N
can be improved.

[0023]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, and is a diagram showing the surroundings of a stretcher and a magnetic bubble detection element. Further, FIG. 2 is an explanatory diagram showing an example of a rotating magnetic field generated by a current in which a triangular wave and an offset current are superimposed upon reading.

Now, with reference to FIG. 3 and subsequent figures, the positional relationship between the stretcher and the magnetic bubble detection element, the magnetic field rotation direction, the bubble detection phase, and the offset relationship will be explained in detail in each case.

FIG. 3 is a diagram showing the relationship between the stretcher S and the magnetic bubble detection element 12 and the direction of the magnetic field. Figure 4
is a diagram showing the relationship between the noise and the detection signal when the rotating magnetic field is rotated in the CW direction in FIG. 3, and FIG. 5 is a diagram showing the relationship between the noise and the detection signal when the rotating magnetic field is rotated in the CCW direction in FIG. FIG. In these figures, the bias magnetic field HB is directed from the back to the front of the paper, and the magnetic bubble is the south pole. In this case, the detection signal detected by the magnetic bubble detection element 12 (13) is generated when the magnetic field is directed in the X direction of the stretcher on which the magnetic bubble detection element 12 is placed. In addition, the phase at which switching noise occurs is determined only by the rotation direction of the rotating magnetic field.
The position of the stretcher S and the magnetic bubble detection element 12 and the direction of the bias magnetic field are irrelevant.

By adding the offset Hx in the X direction to the right in the figure, it is possible to quickly escape from the dead zone in the Hx direction sensitivity curve of the magnetic bubble detection element. Therefore, the detection signal rises quickly, and the width of the detection signal can be widened.

On the other hand, by adding the offset Hy in the Y direction upward in the figure, the timing of the noise added to the detection signal (switching noise generated by the magnetic bubble detection element itself) and the timing of the fall of the detection signal can be adjusted. can be separated, and the S/N can be improved. Figure 3
In this configuration, it is preferable to rotate the magnetic field in the CW direction (as shown in FIG. 4).

FIG. 6 is a diagram showing a case where the position of the magnetic bubble element 12 with respect to the stretcher is different from that in FIG. 3. In this case, by adding the X-direction offset Hx to the left in the figure, it is possible to quickly escape from the dead zone in the Hx-direction sensitivity curve of the magnetic bubble detection element. Therefore, the detection signal rises quickly, and the width of the detection signal can be widened.

On the other hand, by adding the offset Hy in the Y direction upward in the diagram, the timing of the noise added to the detection signal (switching noise generated by the magnetic bubble detection element itself) and the timing of the fall of the detection signal can be adjusted. can be separated, and the S/N can be improved. Therefore, in the configuration of FIG. 6, the magnetic field is rotated in the CCW direction (
(shown in FIG. 8) is preferred.

FIG. 9 is a diagram showing a case where the direction of the stretcher is different from that in FIGS. 3 and 6. In this case, by adding the X-direction offset Hx to the right in the figure, it is possible to quickly escape from the dead zone in the Hx-direction sensitivity curve of the magnetic bubble detection element. Therefore, the detection signal rises quickly, and the width of the detection signal can be widened.

On the other hand, by adding the offset Hy in the Y direction toward the bottom of the figure, the timing of the noise added to the detection signal (switching noise generated by the magnetic bubble detection element itself) and the timing of the fall of the detection signal can be adjusted. can be separated, and the S/N can be improved. Therefore, in the configuration of FIG. 9, the magnetic field is rotated in the CCW direction (
(shown in FIG. 11) is preferable.

FIG. 12 is a diagram showing a case where the position of the magnetic bubble element 12 with respect to the stretcher is different from that in FIG. 9. In this case, by adding the X-direction offset Hx to the left in the figure, it is possible to quickly escape from the dead zone in the Hx-direction sensitivity curve of the magnetic bubble detection element. Therefore, the detection signal rises quickly, and the width of the detection signal can be widened.

On the other hand, by adding the offset Hy in the Y direction toward the bottom of the figure, the timing of the noise added to the detection signal (switching noise generated by the magnetic bubble detection element itself) and the timing of the fall of the detection signal can be adjusted. can be separated, and the S/N can be improved. Therefore, in the configuration of FIG. 12, the magnetic field is rotated in the CW direction (
(shown in FIG. 13) is preferred.

From the above, the offset direction suitable for readout (in which the signal width of the detection signal can be widened) is as follows.

Hx offset: Determined by the positional relationship between the stretcher and the magnetic bubble detection element. That is,
This is the direction in the X direction of the side where the magnetic bubble detection element is arranged in the stretcher. ...■ Hy offset: Determined by the positional relationship between the stretcher and the magnetic bubble detection element and the direction of magnetic field rotation. That is, from the direction of the X direction on the side where the magnetic bubble detection element is arranged in the stretcher, 9
The orientation is in the Y direction as if rotated by 0 degrees. ...■Also, the direction of rotation of the magnetic field suitable for readout (which allows for a wide signal width) is the direction in which the bubbles rise from the bottom to the top of the ridgeline on the side where the magnetic bubble detection element is placed in the stretcher. be. ...■ Next, with reference to FIG. 15 and subsequent figures, a case will be described in which the bias magnetic field HB is directed from the front to the back of the paper and the magnetic bubble is the north pole. In this case, the magnetic bubble detection element 12 (1
The detection signal detected by 3) is generated when the magnetic field is oriented in the opposite direction to the X direction of the stretcher in which the magnetic bubble detection element 12 is placed. Further, the phase at which switching noise occurs is determined only by the rotational direction of the rotating magnetic field, and is unrelated to the positions of the stretcher S and the magnetic bubble detection element 12 and the direction of the bias magnetic field.

By adding the X-direction offset Hx to the left in the figure, it is possible to quickly escape from the dead zone in the Hx-direction sensitivity curve of the magnetic bubble detection element. Therefore, the detection signal rises quickly, and the width of the detection signal can be widened.

On the other hand, by adding the offset Hy in the Y direction toward the bottom of the diagram, the timing of the noise added to the detection signal (switching noise generated by the magnetic bubble detection element itself) and the timing of the fall of the detection signal can be adjusted. can be separated, and the S/N can be improved. Figure 1
In configuration No. 5, it is preferable to rotate the magnetic field in the CW direction (as shown in FIG. 16).

FIG. 18 is a diagram showing a case where the position of the magnetic bubble element 12 with respect to the stretcher is different from that in FIG. 15. In this case, by adding the X-direction offset Hx to the right in the figure, it is possible to quickly escape from the dead zone in the Hx-direction sensitivity curve of the magnetic bubble detection element. Therefore, the detection signal rises quickly, and the width of the detection signal can be widened.

On the other hand, by adding the offset Hy in the Y direction toward the bottom of the figure, the timing of the noise added to the detection signal (switching noise generated by the magnetic bubble detection element itself) and the timing of the fall of the detection signal can be adjusted. can be separated, and the S/N can be improved. Figure 1
In configuration No. 8, the magnetic field is rotated in the CCW direction (Fig. 20
) is preferred.

FIG. 21 is a diagram showing a case where the direction of the stretcher is different from that in FIGS. 15 and 18. In this case,
By adding the directional offset Hx to the left in the figure, it is possible to quickly escape from the dead zone in the Hx directional sensitivity curve of the magnetic bubble detection element. Therefore, the detection signal rises quickly, and the width of the detection signal can be widened.

On the other hand, by adding the offset Hy in the Y direction upward in the diagram, the timing of the noise added to the detection signal (switching noise generated by the magnetic bubble detection element itself) and the timing of the fall of the detection signal can be adjusted. can be separated, and the S/N can be improved. Therefore, in the configuration of FIG. 21, it is preferable to rotate the magnetic field in the CCW direction (as shown in FIG. 23).

FIG. 24 is a diagram showing a case where the position of the magnetic bubble detection element 12 with respect to the stretcher is different from that in FIG. 21. In this case, by adding an offset Hx in the X direction to the right in the figure, Hx of the magnetic bubble detection element is
You can quickly get out of the dead zone in the directional sensitivity curve. Therefore, the detection signal rises quickly, and the width of the detection signal can be widened.

On the other hand, by adding the offset Hy in the Y direction upward in the figure, the timing of the noise added to the detection signal (switching noise generated by the magnetic bubble detection element itself) and the timing of the fall of the detection signal can be adjusted. can be separated, and the S/N can be improved. Figure 2
In configuration No. 4, it is preferable to rotate the magnetic field in the CW direction (as shown in FIG. 25).

From the above, the offset direction suitable for readout (the signal width of the detection signal can be widened) is as follows.

Hx offset: Determined by the positional relationship between the stretcher and the magnetic bubble detection element. That is,
This is the direction in the X direction opposite to the side where the magnetic bubble detection element is arranged in the stretcher. ...■ Hy offset: Determined by the positional relationship between the stretcher and the magnetic bubble detection element and the direction of magnetic field rotation. That is, the orientation is in the Y direction, which is rotated 90 degrees in the magnetic field rotation direction from the X direction orientation on the side where the magnetic bubble detection element is arranged in the stretcher. ...■Also, the direction of rotation of the readout magnetic field suitable for readout (which allows a wide signal width) is the direction in which the bubbles rise from the bottom to the top of the ridgeline on the side where the magnetic bubble detection element is placed in the stretcher. It is. ...■ Therefore, the direction of this rotating magnetic field does not change even if HB changes (■=■).

FIG. 27(a) shows an outline of the eye pattern of the detection signal waveform when an offset is given according to the offset conditions (■, ■, ■, ■) determined as above.
FIG. 27(b) shows the eye pattern of the detection signal waveform without offset, and FIG. 27(c) shows the eye pattern of the detection signal when an offset is applied, contrary to this embodiment. As is clear from these figures, it can be seen that the offset direction of this embodiment is effective.

[0048] In accordance with the above conditions, either an X or Y offset may be added. It is also possible to generate an offset magnetic field by tilting the bias magnet.

Furthermore, although the current waveform applied to the readout coil has been described as a triangular wave, there is no problem in using a sine wave as well. As the stretcher S, a chevron stretcher in which the chevron stretchers are butted as shown in FIG. 28 was used in the explanation, but a nested chevron stretcher shown in FIG. It is also possible.

[0050]

As described above in detail, according to the magnetic bubble detection method of the present invention, a magnetic bubble detection signal and noise can be separated, and a stable and wide magnetic bubble detection signal can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing the entire magnetic bubble element.

FIG. 2 is a waveform diagram showing an example of a current waveform applied to a readout coil.

FIG. 3 is an explanatory diagram showing the positional relationship between a stretcher and a magnetic bubble detection element.

FIG. 4 is an explanatory diagram showing the relationship between a detection signal and an offset in the configuration shown in FIG. 3;

FIG. 5 is an explanatory diagram showing the relationship between a detection signal and an offset in the configuration shown in FIG. 3;

FIG. 6 is an explanatory diagram showing the positional relationship between a stretcher and a magnetic bubble detection element.

FIG. 7 is an explanatory diagram showing the relationship between a detection signal and an offset in the configuration shown in FIG. 6;

FIG. 8 is an explanatory diagram showing the relationship between a detection signal and an offset in the configuration shown in FIG. 6;

FIG. 9 is an explanatory diagram showing the positional relationship between a stretcher and a magnetic bubble detection element.

FIG. 10 is an explanatory diagram showing the relationship between a detection signal and an offset in the configuration shown in FIG. 9;

FIG. 11 is an explanatory diagram showing the relationship between a detection signal and an offset in the configuration shown in FIG. 9;

FIG. 12 is an explanatory diagram showing the positional relationship between the stretcher and the magnetic bubble detection element.

13 is an explanatory diagram showing the relationship between a detection signal and an offset in the configuration shown in FIG. 12. FIG.

14 is an explanatory diagram showing the relationship between a detection signal and an offset in the configuration shown in FIG. 12. FIG.

FIG. 15 is an explanatory diagram showing the positional relationship between a stretcher and a magnetic bubble detection element.

16 is an explanatory diagram showing the relationship between a detection signal and an offset in the configuration shown in FIG. 15. FIG.

17 is an explanatory diagram showing the relationship between a detection signal and an offset in the configuration shown in FIG. 15. FIG.

FIG. 18 is an explanatory diagram showing the positional relationship between the stretcher and the magnetic bubble detection element.

19 is an explanatory diagram showing the relationship between a detection signal and an offset in the configuration shown in FIG. 18. FIG.

FIG. 20 is an explanatory diagram showing the relationship between the detection signal and offset in the configuration shown in FIG. 18;

FIG. 21 is an explanatory diagram showing the positional relationship between a stretcher and a magnetic bubble detection element.

22 is an explanatory diagram showing the relationship between a detection signal and an offset in the configuration shown in FIG. 21. FIG.

FIG. 23 is an explanatory diagram showing the relationship between a detection signal and an offset in the configuration shown in FIG. 21;

FIG. 24 is an explanatory diagram showing the positional relationship between the stretcher and the magnetic bubble detection element.

25 is an explanatory diagram showing the relationship between the detection signal and offset in the configuration shown in FIG. 24. FIG.

26 is an explanatory diagram showing the relationship between a detection signal and an offset in the configuration shown in FIG. 24. FIG.

FIG. 27 is an explanatory diagram showing a comparison of eye patterns of detection signals when the offset is changed.

FIG. 28 is an explanatory diagram showing an example of arrangement of stretchers.

FIG. 29 is an explanatory diagram showing an example of arrangement of stretchers.

FIG. 30 is an explanatory diagram showing an example of arrangement of stretchers.

FIG. 31 is an explanatory diagram showing the arrangement around the magnetic bubble element.

FIG. 32 is an explanatory diagram showing the arrangement of a stretcher and a magnetic bubble detection element.

FIG. 33 is an explanatory diagram showing in detail the arrangement of a stretcher and a magnetic bubble detection element.

FIG. 34 is an explanatory diagram showing the intensities of a bias magnetic field and a rotating magnetic field.

FIG. 35 is a characteristic diagram showing the characteristics of a magnetic bubble detection element.

FIG. 36 is a perspective view showing the area around the magnetic bubble detection element.

FIG. 37 is a circuit diagram showing a circuit configuration for generating a magnetic field for reading.

FIG. 38 is a waveform diagram showing a detection signal.

FIG. 39 is an explanatory diagram showing a Hy direction sensitivity curve of a magnetic bubble detection element.

FIG. 40 is an explanatory diagram showing a Hx direction sensitivity curve of a magnetic bubble detection element.

[Explanation of symbols]

1 Magnetic bubble element 2,2′ bias magnet 3, 4 Readout coil 5 Ring magnet 12, 13 Magnetic bubble detection element S Stretcher

Claims (1)

[Claims] Claim 1: Using a stretcher and a thin film type magnetic bubble detection element using magnetoresistive effect, the magnetic bubbles are forcibly moved by generating a rotating magnetic field in the readout coil, and the bit pattern of the magnetic bubbles is changed into a magnetic bubble. In the magnetic bubble detection method that uses a detection element, when a bias magnetic field is applied from the back side of the magnetic bubble element toward the front side, the direction in which the magnetic bubble detection element is placed in the stretcher, among the sensitivity directions of the detection element, is The DC component and the rotating magnetic field for moving the magnetic bubble within the plane of the magnetic bubble detection element are in the opposite direction from this direction.
A rotating magnetic field rotated by 0 degrees and having a DC component perpendicular to the sensitivity direction of the magnetic bubble detection element is applied to the magnetic bubble element, and a bias magnetic field is applied from the front surface to the back surface of the magnetic bubble element. Sometimes, there is a direct current component in the direction of sensitivity of the detection element that is opposite to the direction in which the magnetic bubble detection element is arranged in the stretcher, and a direct current component that is in the direction of the magnetic bubble detection element from the direction in which the detection element is arranged. A magnetic bubble detection method in which a rotating magnetic field is applied to a magnetic bubble element such that the rotating magnetic field is rotated 90 degrees in the direction of the rotating magnetic field for moving the magnetic bubble element and has a direct current component perpendicular to the sensitivity direction of the magnetic bubble detecting element.