JPS5846765B2 - Jikihed - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic head that utilizes the so-called magnetoresistive effect, in which the electrical resistance value changes when a magnetic field is applied to a ferromagnetic material such as permalloy.

As a principle structure of a magnetic head that utilizes this magnetoresistive effect, a structure as shown in FIG. 1 has been conventionally considered.

That is, in FIG. 1A, the magnetoresistive element 2 made of a ferromagnetic thin plate is brought into contact with or close to the magnetic tape, which is the recording medium 1, in the perpendicular y direction, and the magnetoresistive element 2 is moved in the longitudinal direction (Z direction). Electrodes 3 and 4 are arranged at both ends, and electrodes 3 and 4 are arranged at both ends.
In this method, a constant current j is passed between the electrodes 3 and 4, and a change in resistance value in the Z direction is detected from a change in voltage between the electrodes 3 and 4 using a signal magnetic field in the y direction of the recording medium 1.

In this method, the recording medium 1 in the y direction of the magnetoresistive element 2
If the distance from The signal magnetic field attenuation becomes extremely large.

As a way to avoid such attenuation, if the magnetoresistive element 2 is arranged parallel to the recording medium 1 as shown in the opening of Figure 1, the separation loss in the y direction will almost disappear, but the magnetoresistive element 2 is generally Since it is a thin plate, wear due to sliding with the recording medium 1 becomes a problem, which poses a practical problem.

Further, the resistance change Δρ due to the magnetoresistive effect has the following relational expression, where θ is the angle between the magnetization direction of the ferromagnetic thin plate and the current direction, and a and b are constants.

Furthermore, the relationship between the applied magnetic field H and the resistance change rate △ρ/△ρmaX has the characteristics shown in Figure 2, and the signal magnetic field and the resistance change rate have extremely nonlinear characteristics, and this nonlinearity and the dynamic range In order to make this as wide as possible, it is necessary to apply a bias magnetic field Hb and set the operating point to point P in FIG.

The present invention solves these problems, and examples thereof will be described below with reference to the drawings.

In FIG. 3, a ferromagnetic thin plate 6 is constructed to form a closed magnetic circuit having a magnetic gap 5 having a predetermined width g in a part thereof.

Further, a substantially linear portion I is formed in a part of this closed magnetic circuit.

Detection electrodes 8 and 9 are provided at both ends of the linear portion, that is, separated by a predetermined distance in the direction in which the magnetic flux of the closed magnetic circuit flows.

Reference numeral 12 denotes a permanent magnet, which is arranged close to the linear portion 7 of the ferromagnetic thin plate 6, as shown in the figure.

With the above configuration, the signal magnetic flux from the recording medium (not shown) is picked up through the air gap 5, and since the magnetic thin plate forms a closed magnetic circuit, the signal magnetic flux is located at a distance from the recording medium. It is also effectively guided to the linear portion.

Therefore, a change in the electrical resistance value of the linear portion 7 according to the signal magnetic flux flowing through the linear portion 7 can be detected as a voltage change between the detection electrodes.

Further, the linear portion 7 of the ferromagnetic thin plate 6 that acts as a magnetoresistive element is uniaxially anisotropically oriented, and its easy magnetization direction coincides with the direction of the arrow 10, that is, the direction in which the signal magnetic flux flows and the direction of the detection current. I'm letting you do it.

Further, a magnet 12, for example, is provided to apply a bias magnetic field in a direction (arrow 11) perpendicular to the easy magnetization direction.

On the other hand, from the relationship between the specific resistance value ρ of the magnetoresistive element and the angle θ between the magnetization direction of the ferromagnetic thin plate of the element and the current, the relationship between the angle change and the resistance change is as shown in Figure 5. maximum when

That is, the operating point can be set at a location where the magnetic sensing element has the best sensitivity to the applied magnetic field and a wide dynamic range.

Note that the resistance change in Fig. 5 is the maximum value of resistance change △ρmax
It is normalized and shown.

In consideration of such operating characteristics, when the bias magnetic field Hb of a predetermined value is applied, the direction of magnetization of the straight portion 7 can be set to an operating point inclined at approximately 45 degrees from the orientation direction.

In order to detect a large change in electrical resistance due to a signal magnetic field, it is desirable that the resistance value of the magnetoresistive element be as high as possible, so it is a good idea to configure the element so that the longitudinal direction of the element matches the direction of the current.

As described above, according to the present invention, it is possible to create a structure in which the bias magnetic field applied to the magnetoresistive element does not affect the recording medium, and also because the longitudinal direction of the element coincides with the direction of the signal magnetic flux. It is possible to operate with a configuration in which the influence of the demagnetizing field due to the element shape is extremely reduced.

Furthermore, since the easy magnetization direction of the magnetic thin film and the signal magnetic flux passing direction are made to coincide with each other, it is possible to obtain a magnetoresistive magnetic head with a simple structure.

[Brief explanation of the drawing]

Fig. 1A is a perspective view showing a conventional magnetoresistive magnetic head, Fig. 2 is an explanatory view of the same operation, Fig. 3 is a perspective view schematically showing an embodiment of the present invention, and Fig. 4 is a perspective view showing a conventional magnetoresistive magnetic head. The figure is a perspective view of the same main part, and FIG. 5 is a diagram showing the relationship between the rate of change in electrical resistance and the magnetization rotation angle of the magnetoresistive element. 5...Magnetic air gap, 6...Ferromagnetic thin plate (
magnetoresistive effect element), 8, 9... detection electrode,
12... Magnet.

Claims (1)

[Claims] 1 A closed magnetic circuit having a magnetic air gap in a part is constructed using a ferromagnetic thin plate, and a detection electrode is provided a predetermined distance apart in the direction of the signal magnetic flux passing through this closed magnetic circuit, and a detection electrode is provided between the two electrodes. A permanent magnet is placed close to a portion of the ferromagnetic thin plate that does not include a magnetic gap, a bias magnetic field is applied in a direction perpendicular to the direction of current flowing through the portion, and the direction in which the signal magnetic flux flows is set as the easy magnetization direction. A magnetic head characterized by: