JPS592086B2 - Jikihed - Google Patents

Description

[Detailed description of the invention] The present invention extracts recorded information from a magnetic recording medium as magnetostriction,
The present invention relates to improvements in magnetic heads that drive ferroelectric materials to obtain electrical signals.

The basic structure of a magnetic head that utilizes the magnetoresistive effect in which the electrical resistance value changes when a magnetic field is applied to a ferromagnetic material was considered to be as shown in FIG. 1.

In FIG. 1, a magnetoresistive element 2 made of a ferromagnetic thin plate is placed in contact with or close to the recording medium 1 in the y direction perpendicular to the recording medium 1, and electrodes 3 are placed at both ends of the magnetoresistive element 2 in the longitudinal direction, that is, in the z direction.
, 4 are arranged, a current i is caused to flow through the element, and a method is considered in which the voltage change between the electrodes 3 and 4 is detected. Further, the specific resistance change Δρ due to the magnetoresistive effect has a relationship of Δρ2a+b−cos2θ, where θ is the angle between the magnetization direction of the ferromagnetic thin plate and the current direction, and a and b are constants. The relationship between the applied magnetic field H and the resistance change rate Δρ/Δmax is the second
The characteristics are as shown in the figure, and the signal magnetic field and the rate of change in resistance are extremely non-linear.In order to widen this non-linearity and the dynamic wrench as much as possible, a bias magnetic field Hb is applied, and the operating point is set as shown in Figure 2. It is necessary to set it at point p. In such a configuration, in order to set the bias magnetic field, there is a method of adjusting the leakage magnetic field from a hard magnetic material that becomes a permanent magnet, and a method of adjusting the bias magnetic field by changing the current property using a magnetic field generated by a current. Note that the vertical axis in FIG. 2 can also be expressed as the mechanical dimensional deformation rate (Δl/Δlmax) related to the magnetostrictive effect of the ferromagnetic thin plate.

In the conventional output voltage extraction method described above, by passing a detection current i through the magnetoresistive element, the output voltage e is determined by e=Δρ·e−i/S, where the length of the element is e and the cross-sectional area is S.
In order to increase the output voltage, it is necessary to increase l as much as possible, but there is a limit due to the thermal limitations of the element, and especially when the cross-sectional area of the element is large, the allowable current of the element If the density is J, then J-l/S becomes small and the output voltage e becomes small, so the element cross-sectional area becomes extremely small, causing problems such as element disconnection and deterioration due to chemical alteration.

Furthermore, since it is necessary to flow a detection current, power consumption becomes a problem. This is an important issue especially when a multi-channel configuration is used. Furthermore, since it is necessary to operate with a constant current, the detection current is required to have sufficiently little ripple current, which has the disadvantage that the current source is expensive. The present invention solves the above drawbacks by using a magnetoresistive element with large magnetostriction.

An embodiment of the present invention will be described below with reference to the drawings. Figure 3A is a perspective view, and the mouth is a slightly modified cross-sectional view of Figure 3A. A conductive non-magnetic thin plate 6 is placed on a ferromagnetic substrate 5 made of a soft magnetic material or on a non-magnetic substrate with a ferromagnetic thin plate attached, with the width direction of the recording medium 1 being the longitudinal direction, and perpendicular to the recording medium 1. A ferromagnetic thin plate 8 is arranged with an insulating layer 7 in between, forming a closed magnetic path with a gap width equal to the sum of the thickness of the conductive non-magnetic thin plate 6 and the thickness of the insulating layer 7. A ferroelectric thin plate 10 is adhered to the surface via an insulating layer 9, and electrodes 11 and 12 for output voltage extraction are arranged at both ends of the ferroelectric thin plate 10. The signal magnetic flux from the recording medium 1 is detected in the air gap, and the magnetic flux flows through the ferromagnetic thin plate 8. Due to the magnetostrictive effect, the ferromagnetic thin plate causes a length variation of Δe/e, and this length variation causes the adjacent ferroelectric material to change in length. An output voltage corresponding to the signal magnetic flux from the recording medium 1 is obtained by the piezoelectric effect of the thin plate 10. In order to apply a bias magnetic field as shown in FIG. 2, a bias magnetic field is applied to the ferromagnetic thin plate 8 by passing a current 1B through the conductive non-magnetic thin plate 6, which is a gap material. In order to perform such an operation efficiently, it is desirable that the ferromagnetic thin plate 8 has a high magnetic permeability, and at the same time, it is also desirable that it has a large magnetostriction constant. For example, Fe
-Ni alloy permalloy, Nl-CO alloy, Ni, and other ferromagnetic materials are suitable. Also, as a ferroelectric material, C
6S, BaTiO3, Pb(Zrx-Til-x)03
, PCM and other materials with a large piezoelectric effect are suitable. In the above embodiment, since the longitudinal effect is used as the piezoelectric effect of the ferroelectric material 10, the output voltage extraction electrode 1
1 and 12 are provided with an insulating layer 9 because they are arranged on the longitudinal plane of the piezoelectric effect element, but the insulating layer 9 is not necessarily required if the effect of the piezoelectric effect is used.

Further, in this drawing, the ferromagnetic thin plate is arranged only on one side of the non-magnetic gap material, but it is possible to arrange it on both sides.
Further, the output voltage extraction electrode from the piezoelectric effect element is not limited to this specific example, and various configurations can be considered. With the above configuration, the operating point of the ferromagnetic thin plate 8, which becomes a magnetoresistive element or a magnetostrictive element, is determined by the applied magnetic field H and the mechanical deformation rate of the element (Δe/Δ
The linearity with ErI]AX) is improved.

Unlike conventional magnetoresistive elements, no current is required for voltage detection, so power consumption of the magnetic head is eliminated. This is a particularly advantageous condition in a multi-head configuration in which a large number of unit magnetic heads are arranged. Since no current is required, it has excellent features such as being free from the effects of ripples in the power supply current, which solves the problems of noise contamination and reduction in signal-to-noise ratio caused by ripples.
Furthermore, conventionally, the current flowing through the magnetoresistive element heats the element, causing chemical and physical deterioration, but this problem is also solved. Furthermore, since the magnetic head of the present invention detects the signal magnetic flux from the recording medium 1 in the gap, it is possible to avoid the width loss of the magnetoresistive element arranged perpendicular to the medium, which has been a problem in the past. . It has the following effects. Furthermore, in the present invention, a magnetic closed circuit is constructed using a ferromagnetic thin plate, and a ferroelectric substance is attached to the side surface of the ferromagnetic thin plate, so that the magnetic field applied to each part of the ferroelectric substance is uniform at any given time. , it becomes possible to reproduce faithful electrical signals. Since the bias current passing conductor layer constitutes a magnetic gap, not only the structure is simplified, but also the film can be made even thinner. C. By adjusting the bias current flowing through this conductor layer, the optimum bias point can be easily obtained.

[Brief explanation of the drawing]

Figure 1 shows a conventional example of a magnetoresistive head;
This figure is a diagram showing the relationship between the rate of change in resistance or the rate of change in mechanical shape of a ferromagnetic thin plate, and FIG. 3 is a diagram showing the configuration of a magnetic head according to an embodiment of the present invention. 5... Soft magnetic ferromagnetic thin plate, 6... Conductive non-magnetic thin plate, 7, 9... Insulating layer, 8...
...Ferromagnetic thin plate, 10... Ferroelectric thin plate.

Claims (1)

[Claims] 1. A magnetic material including at least a ferromagnetic thin plate is arranged around the bias current passing conductor, and the bias current passing conductor becomes a magnetic gap and is exposed to the magnetic recording body side,
A magnetic head characterized in that a ferroelectric material is brought into close contact with a side surface of the ferromagnetic thin plate, magnetostriction of the ferromagnetic thin plate is applied to the ferroelectric material, and an electric signal is extracted from the ferroelectric material.