JPH08203032A - Magneto-resistance effect reproducing head - Google Patents

Abstract

PURPOSE: To suppress the generation of Barkhausen noise and to improve the symmetry of an offtrack characteristic by making the influence of a bias magnetic field and the diamagnetic field generated by magnetization of the magnetosensitive part itself uniform. CONSTITUTION: This reproducing head is provided with a magneto-resistance layer 10 having the central part magnetosensitive region 11 having an elliptic shape for detecting the leakage magnetic field from a medium. This resistance layer 10 has the region 11 and an end part magnetic domain control region 12 for controlling the generation of the Barkhausen noise by controlling the magnetic domain structure the central part magnetosensitive region. The longitudinal direction bias is generated by a hard magnetic material layer 30 which is formed in parallel with the resistance layer 10 and comes into direct contact with the end part magnetic domain control region 12. The transverse direction bias is generated by a shunt film 20 and SAL film 21 in parallel with the resistance layer 10. The influence of the bias magnetic field and the diamagnetic field generated by the magnetization of the magnetosensitive part itself is then made uniform. Consequently, the generation of the Barkhausen noise is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing head for reading an information signal from a magnetic recording medium, and more particularly to an improved magnetoresistive effect reproducing head.

[0002]

2. Description of the Related Art Conventionally, a magnetic reading converter called a magnetoresistive (MR) sensor or a head is known. It is known that such sensors can read data from magnetic surfaces of high linear density. M
The R sensor uses the resistance change of a read element made of a magnetoresistive material to detect a magnetic signal as a function of the amount and direction of magnetic flux sensed by the element.

The prior art discloses that it is necessary to apply two bias magnetic fields for the MR element to operate optimally. One is to apply a lateral bias magnetic field to the MR element so that the response to the magnetic flux becomes linear. This bias magnetic field is perpendicular to the plane of the magnetic medium and has a flat MR.
It is parallel to the surface of the device. The other is a vertical bias applied in parallel with the surface of the magnetic medium and in the longitudinal direction of the MR element in order to suppress Barkhausen noise caused by multi-domain effect in the MR element.

Many biasing methods and devices for MR sensors have been developed in the prior art. However, as the recording density has increased, it has become necessary to narrow the recording track and increase the linear recording density along the track. Small MR sensors that meet these requirements cannot be realized using conventional techniques.

A conceptual solution to these prior art problems has been obtained by implementing patterned longitudinal biasing. This solution is described in JP-A-60-59518 and JP-A-2-220213. Simply put,
In the above-mentioned conventional example, the end region of the MR layer is brought into an appropriate single domain state, and as a result, the single domain state is induced in the central magnetic sensitive region of the MR layer. This can be realized by providing a ferromagnetic band layer having a coercive force larger than that of the MR film in contact with the end region of the MR layer to generate a longitudinal bias only in the end region. In an embodiment of this concept, the longitudinal bias is realized by ferromagnetic exchange coupling or magnetostatic coupling between the hard magnetic layer and the soft magnetic MR layer.

[0006]

In all of these conventional techniques, attention is paid to the sensitivity of the head or suppression of Barkhausen noise of the head, but the sensitivity distribution in the track width direction is as shown in FIG. It becomes asymmetrical. However, in order to use it as a servo signal reading head for positioning, symmetry of off-track characteristics is required. One of the factors that deteriorate the symmetry of the off-track characteristics is the non-uniformity of the demagnetizing field at the end of the magnetic sensitive section.

An object of the present invention is to obtain a magnetoresistive effect reproducing head suitable for use as a servo signal reading head for positioning and having a good symmetry of off-track characteristics.

[0008]

In order to solve the above-mentioned problems, the present invention does not form the central magnetic field sensing portion and / or the lateral bias film or both of them with polygons as in the prior art, but rotates them. This can be achieved by forming an ellipsoid or an ellipse having a uniform thickness or a polygon approximating an ellipse to reduce the influence of non-uniformity of the demagnetizing field at the end of the magnetic sensitive section.

[0009]

FIG. 4 schematically shows a demagnetizing field when a lateral bias is applied to a conventional rectangular MR head. The lateral bias magnetic field causes the magnetization of the magnetic sensitive region to be inclined by about 45 degrees, and the longitudinal bias magnetic field causes the magnetization of the magnetic domain control region to be oriented in the longitudinal direction of the film. The demagnetizing field created in the magnetic sensitive portion having such a rectangular magnetized state is smaller in the lower right portion than in the lower left portion of the MR film. The reason why the sensitivity distribution in the track width direction is asymmetric between left and right is that the effect of the demagnetizing field is different between the left and right in the lower part of the MR film where the effect of the leakage magnetic field from the medium is strong.

According to the present invention, by forming the shape of the central magnetic sensing portion and / or the lateral bias film or both into a spheroid or an ellipse of uniform thickness or a polygon approximating an ellipse, Since the influence of the demagnetizing field of the magnetic sensitive section and / or the lateral bias film or both of them can be made uniform, it is possible to obtain a magnetoresistive effect reproducing head having good symmetry of off-track characteristics.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical magnetoresistive effect reproducing head according to the present invention, as shown in FIG. 1, has a magnetoresistive layer 10 having an oval central magnetic sensitive area 11 for detecting a leakage magnetic field from a medium. Characterized by Magnetoresistive layer 10
Are divided into a central magnetic sensitive region 11 and an end magnetic domain control region 12 for controlling the magnetic domain structure of the central magnetic sensitive region and controlling the generation of Barkhausen noise.

FIG. 2 is a sectional view of a typical magnetoresistive effect reproducing head according to the present invention.
Lateral bias application shunt film 20, SAL film 21,
It comprises a hard magnetic layer 30 for longitudinal bias application and an electrode layer 40. In this example, the SAL film was also formed into an elliptical shape. The head was formed by a sputtering method, and a mask was used to form the head into an elliptical shape.

Here, the longitudinal bias is the magnetoresistive layer 10.
And is generated by the hard magnetic layer 30 that is in parallel with the edge magnetic domain control region 12 and is in direct contact with the end magnetic domain control region 12. Further, the lateral bias is applied to the shunt film 20 and SAL parallel to the magnetoresistive layer 10.
It is generated by the membrane 21. The electrode layer 40 is an electric path for transmitting a signal detection current and a bias current to the magnetoresistive layer 10 and the shunt film 20 and transmitting an output signal to an external electric circuit.

In this embodiment, the magnetoresistive layer has a thickness of 5 to 20 nm, the hard magnetic layer has a thickness of 10 to 100 nm, and the shunt film has a thickness of 10 to 40 nm. The distance T between the inner end surfaces of the electrode was 5 μm, and the distance W between the inner surfaces of the hard magnetic body was 7 μm. The magnetoresistive layer was formed in an elliptical shape having a long diameter W of 7 μm and a short diameter, that is, a height H of 6 μm. The magnetoresistive layer is N
The i-Fe alloy, the hard magnetic layer was a CoPtCr alloy, and the shunt film was an Nb film. For the hard magnetic layer, a Co alloy-based magnetic recording medium material was effective.

FIG. 3 shows the sensitivity distribution in the track width direction of the head of this embodiment and the conventional head. In the figure, a shows the sensitivity distribution in the track width direction of the MR head of this embodiment, and b shows the sensitivity distribution in the track width direction of the conventional MR head. In this measurement, the reproduction output was measured while moving the medium recorded in an area narrower than the track width of the MR head in the track width direction. As a recording head, a magnetic induction type head having a track width of 0.5 μm (IEEE Trans. Magn.) Vol. 27, 4678 (1
991)) was used.

From the figure, it can be seen that the sensitivity distribution in the track width direction of the conventional MR head has a greater left-right asymmetry than the sensitivity distribution in the track width direction of the MR head of this embodiment. In fact, the sensitivity peak of the MR head of this embodiment is in the center of the head, whereas the sensitivity peak of the conventional MR head is 12.5% to the left of the center.

The same effect can be obtained by using any of the current bias method, the shunt bias method, the soft bias method, and the SAL bias method as a method for applying the lateral bias magnetic field to the MR element. Even if the order of the films is changed, the effect of improving the symmetry is maintained.

In the present embodiment, the central magnetic sensitive area and SA
Both of the L films were formed into an elliptical shape, but the symmetrization effect can be observed with only one of them.

[0019]

The present invention has the effect of reducing the effect by uniformizing the influence of the bias magnetic field and the demagnetizing field generated by the magnetization of the magnetically sensitive portion itself, and the magnetoresistive effect with good symmetry of the off-track characteristics. A mold reproducing head can be obtained.

[Brief description of drawings]

FIG. 1 is a rear view of a main part of a magnetoresistive effect reproducing head according to an embodiment of the present invention.

FIG. 2 is a sectional view of an embodiment of a magnetoresistive effect reproducing head according to the present invention.

FIG. 3 is a sensitivity distribution diagram in the track width direction of the head of the present invention and the conventional head.

FIG. 4 is a schematic diagram of a demagnetizing field in a bias magnetic field in a conventional magnetoresistive effect reproducing head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Magnetoresistive layer, 11 ... Central magnetic field sensitive area, 12 ... Edge magnetic domain control area, 20 ... Shunt film, 21 ... SAL film, 3
0 ... Hard magnetic layer, 40 ... Electrode.

Claims (2)

[Claims] 1. A magnetoresistive layer having a central magnetic sensitive region and an end magnetic domain control region, electrodes connected to both sides thereof, a pattern for generating a lateral bias in the magnetoresistive layer, and a magnetic shield for the magnetoresistive layer. In the magnetoresistive effect reproducing head including a soft magnetic film provided on both sides for supporting the magnetic resistance effect reproducing head, the shape of the central magnetically sensitive portion and / or the lateral bias film is equal to the spheroid or the uniform thickness. 2. A magnetoresistive effect reproducing head characterized by being formed into an elliptical shape or a polygonal shape approximating the elliptical shape. 2. The magnetoresistive effect reproducing head according to claim 1, wherein the magnetoresistive layer operates by a magnetoresistive effect or a giant magnetoresistive effect.