JPS5816265B2 - Entoujikukenshiyutsusouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cylindrical magnetic domain detection device having a cylindrical domain expansion element and a magnetoresistive detection element that utilizes the magnetoresistive effect of a ferromagnetic material.

Conventionally, in a micro cylindrical magnetic domain detection device using a magnetoresistive detection element (a cylinder with a diameter of 10 microns or less; the target is a magnetic domain), ferromagnetic pieces for moving the cylindrical magnetic domain are appropriately arranged to detect the cylindrical magnetic domain. The cylindrical magnetic domain is detected by enlarging the image.

Further, in order to eliminate noise induced by the rotating magnetic field and the magnetic field from the ferromagnetic piece, the noise is eliminated or reduced by differentially connecting a tummy detection element and a tummy detection element.

An example of a conventional cylindrical magnetic domain detection device is the AIP Conference Proceedings published in 1971.
-CEIIDDINGS), volume 5, page 235.

However, in this type of cylindrical magnetic domain detection device, only one effective magnetoresistive element is connected to each expensive differential amplifier, and only one bit signal is detected within one period of the rotating magnetic field. However, it was difficult to obtain a high performance-cost ratio.

In particular, when creating a high-speed, large-capacity storage device, the number of places (or magnetoresistive elements) that detect cylindrical magnetic domains in parallel increases, and the number of differential amplifiers also increases, which reduces the performance cost ratio of the storage device. becomes very bad.

Therefore, the conventional cylindrical magnetic domain detection device has a drawback in that the expensive differential amplifier cannot be used economically and effectively.

A first object of the present invention is to provide a new device configuration that eliminates the above-mentioned defects.

A second object of the present invention is to provide a cylindrical magnetic domain detection device with high reading speed.

According to the present invention, a plurality of cylindrical magnetic domain expanding elements that expand a cylindrical magnetic domain at different times within one cycle of a rotating magnetic field, and at least one magnetic domain expanding element disposed close to each of the cylindrical magnetic domain expanding elements a resistance detection element, a current source that supplies current to the plurality of magnetoresistive detection elements, and a differential amplifier that sequentially amplifies signals from the plurality of magnetoresistive detection elements within the one cycle; A cylindrical magnetic domain detection device including:

FIG. 1 shows a schematic diagram of a conventional cylindrical magnetic domain detection device.

The cylindrical magnetic domain in the cylindrical magnetic domain plate moves according to the rotating magnetic field opening guided by a ferromagnetic thin piece (hereinafter referred to as T or I pattern) 10° 11 arranged closely to the cylindrical magnetic domain plate.

(2) When the pattern moves to 98, 99° 100, the cylindrical magnetic domain is expanded and becomes a cylindrical magnetic domain 500.

When the rotating magnetic field 60 further rotates, the cylindrical magnetic domain 500 is reduced and returns to its original thickness, and is transferred over the TI patterns 12 and 13.

The stray magnetic field of the cylindrical magnetic domain 500 changes the magnetization state of the sensing portion 300 of the magnetoresistive sensing element from its previous state.

At this time, since the electrical resistance of the sensing part 300 changes, when a current is supplied from the current source 40 through the conductor 50, the change in the electrical resistance of the sensing part 300 is converted into a voltage change, and a signal output can be obtained.

However, in addition to the floating magnetic field of the cylindrical magnetic domain 500, the rotating magnetic field 60 and stray magnetic fields from the patterns 9B, 99, 100 for expansion are also applied to the sensing portion 300, and noise from these is mixed into the signal output and the S/N ratio is reduced. Deteriorate.

Therefore, in this conventional cylindrical magnetic domain detection device, a dummy sensing portion 301 is provided, and a dummy enlargement ■ pattern 2 is provided on this.
A floating magnetic field of 00, 201, 202 and a rotating magnetic field 60 are applied.

When a current is applied to the sensing portion 301 from the current source 41 through the conductor 50, a noise voltage is generated there.

When this noise voltage and the signal voltage mixed with the noise are input to the differential amplifier 42, the noise voltage becomes an in-phase input component of the differential amplifier 42 and is therefore eliminated.

Then, only the signal voltage appears at the output terminal 43, and the output signal voltage becomes as shown in FIG.

The T patterns 20 and 21 in FIG. 1 are used to sweep out erroneously incoming cylindrical magnetic domains when they enter the dummy enlarged pattern.

The above is an explanation using a schematic diagram of a conventional cylindrical magnetic domain detection device.

As can be understood from the above explanation, the conventional cylindrical magnetic domain detection device requires two sensing elements, two sets of cylindrical domain expansion patterns, two current sources, and a differential amplification device to detect one bit within one period of a rotating magnetic field. It requires one container and is expensive.

Furthermore, as is clear from FIG. 2, it is not possible to detect one bit of the output signal (Vs) t in one period (T').

That is, in the conventional cylindrical magnetic domain detection device, various elements are not used effectively.

Therefore, there is a drawback that the data transfer rate cannot be increased beyond one bit per period.

FIG. 3 shows a schematic diagram of an embodiment of the present invention, in which four types of cylindrical domain movement paths 1. λ, A
, has a nose.

In the first movement path 1, the cylindrical magnetic domain 30 moves on the TI pattern with the rotation of the rotating magnetic field 90, and is expanded by the enlargement patterns 7Q, 71°72 when the direction of the rotating magnetic field 90 is a. .

The stray magnetic field of the expanded cylindrical domain 30 is sensed by the sensing portion 34 of the magnetoresistive sensing element.

In the second movement path 2, the cylindrical magnetic domain 31 that has moved on the TI pattern is expanded by the enlarged pattern 73°74.75 when the direction of the rotating magnetic field 90 is b, and the stray magnetic field is magnetic; is sensed by the sensing portion 35 of.

Similarly, the cylindrical magnetic domain 32 of the moving path 3 is a rotating magnetic field 90
When the direction of is C, the stray magnetic field is magnified by the magnifying pattern 76°77.7B and is sensed by the sensing portion 36.

The cylindrical magnetic domain 33 of the moving path 4 is expanded by the expansion patterns 79, 80, 81 when the direction of the rotating magnetic field 90 is d, and the stray magnetic field is sensed by the sensing portion 37.

In this way, the cylindrical magnetic domains moving in the movement paths 1, 2, 3.4 are sensed at different phases of the rotating magnetic field.

Since the noise generated in the sensing portion 34 and the noise generated in the sensing portion 36 due to the rotating magnetic field and the magnifying pattern are in the same phase, and the noise generated in the sensing portion 35 and the noise generated in the sensing portion 37 are also in phase, the noise generated in the sensing portion 35 and the sensing portion 37 is also in phase, so that When the wires are connected, the differential amplifier 54 eliminates noise generated from the sensing portions 34, 35, and 36j37.

Sensing sections 34 and 37 are supplied with current from a current source 50, and sensing sections 35 and 36 are supplied with current from a current source 51.

Since the cylindrical magnetic domains 30, 31°, 32.33 are sensed by the sensing parts 34, 35°, 36, 37 with different phases, the signals generated from each sensing part are not canceled and are sent to the differential amplifier 54. The width is increased by

An example of the signal voltage waveform obtained from the differential amplifier 54 is shown in the fourth example.
Illustrated in the diagram.

The vertical axis in the figure is the signal voltage Vs.

In this figure, Pl and P4 are detection signals of the cylindrical magnetic domain 30 and the cylindrical magnetic domain 33 by the sensing portion 34 and the sensing portion 37, respectively, and P2. P3 is a detection signal of the cylindrical magnetic domain 31 and the cylindrical magnetic domain 32 by the sensing portion 35 and the sensing portion 3B.

As can be understood from the above description, the cylindrical magnetic domain detection device according to the present invention can eliminate noise without using a dummy detection element, and can effectively utilize a differential amplifier.

The embodiment of the present invention shown in FIG. 3 has one differential amplifier and two current sources, which is the same number as the conventional device, but it can detect four independent pieces of information. You can get four times the transfer speed.

Magnetoresistive sensing elements are also used effectively.

Although the embodiment describes magnified detection of the rotating magnetic field in four directions, the present invention is not limited to this, but also includes magnified detection in any different directions.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a conventional cylindrical magnetic domain detection device;
The figure shows the detected waveform, FIG. 3 is a schematic diagram showing an embodiment of the cylindrical magnetic domain detecting device according to the present invention, and FIG. 4 shows the detected waveform. In FIG. 3, L2, 3, 4 are travel paths, 30, 31 .
32゜33 is a cylindrical magnetic domain, 34, 35, 36, 37 are sensing parts of magnetoresistive sensing elements, 50.51 is a current source, 54G
-1 differential amplifier, 70 to 81 are expansion patterns.

Claims (1)

[Scope of Claims] 1. A plurality of cylindrical magnetic domain expanding elements that expand cylindrical magnetic domains at different times within one cycle of a rotating magnetic field, and at least one cylindrical magnetic domain expanding element disposed close to each of the cylindrical magnetic domain expanding elements. Magnetoresistive sensing element and multiple pieces in front. a current source that supplies current to each of the magnetoresistive sensing elements;
A cylindrical magnetic domain detection device including a differential amplifier that sequentially amplifies signals from a plurality of the magnetoresistive detection elements within the one cycle.・