JPS62110615A - Thin film magnetic head - Google Patents

Abstract

PURPOSE:To prevent occurrence of Barkhausen noise and obtain reproduced signals of good S/N by providing a coil wound around a magnetic resistance element. CONSTITUTION:Bias magnetic field is impressed to a magnetic resistance element. Signal magnetic field from a recording medium flows through a front yoke 12a, an element 11 and a rear yoke 12b. Sense current is let flow in the element 11 by conductive thin films 13a, 13b and the value of resistance of the element 11 is changed according to the signal magnetic field, and signals on the recording medium can be reproduced by converting the change of resistance to change of voltage. At this time, DC current is flowing in a coil around the element 11, and DC magnetic field is impressed by the current in longitudinal direction of the element. As the magnetic field makes the element 11 single magnetic domain, occurrence of Barkhausen noise caused by discontinuous movement of magnetic domain walls can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetoresistive thin film magnetic head used for reproducing a signal magnetic field recorded on a magnetic recording medium.

2. Description of the Related Art In recent years, magnetoresistive thin-film heads that use magnetoresistive elements have been widely used as playback heads due to the shortening of track widths in magnetic recording devices due to improved track densities and the slowing down of magnetic tape running speeds. be.

FIG. 4 shows an example of a conventional magnetoresistive thin film head (for example, [Magnetoresistive head).
Natoresistive Heads) IIC
EETrans Mag 17 2884 pages). In FIG. 4, 41 is a ferromagnetic substrate, 42 is a first conductive thin film formed on the ferromagnetic substrate 41 and electrically insulated from the ferromagnetic substrate 41, and 43 is a first conductive thin film formed on the first conductive thin film 42. a magnetoresistive element formed electrically insulated from the conductor thin film 42;
44'a- is a front yoke made of a soft magnetic thin film magnetically coupled to the recording medium 46 at the lower end and the magnetoresistive element 43 at the upper end; A rear yoke made of a magnetically coupled soft magnetic thin film, 45 & 4sb are second conductor thin films for flowing a sense current to the magnetoresistive element 43, 46 is a recording medium, and 47 is the traveling direction of the recording medium 46.

Next, the operation will be explained.

A current for applying a bias magnetic field to the magnetoresistive element 43 flows through the first conductive thin film 42 .

The signal magnetic field from the recording medium 46 flows to the front yoke 44a1, the magnetoresistive element 43, and the rear yoke 462L.

At this time, the magnetoresistive element 43 is covered with a second conductor thin film 45a.
, 45b, the resistance value of the magnetoresistive element 43 changes according to the signal magnetic field, and by converting this resistance change into a voltage change, the signal on the recording medium 4θ can be reproduced. .

Generally, the resistance change ΔR of the magnetoresistive element 43 is determined by the angle between the direction of the sense current and the direction of magnetization of the magnetoresistive element 43.
△RI for maximum resistance change! When 12Lx, ΔR=ΔRmlLxCO82θ...
・There is the relationship (1). Further, when the signal magnetic flux density flowing through the magnetoresistive element 43 is 85ig, and the saturation magnetic flux density of the magnetoresistive element 43 is BS, approximately holds true, and (1
) and (2). That is, theoretically, the magnetoresistive element 43 exhibits a resistance change as shown in FIG. 6 in response to a change in the magnetic field. Then, in order to increase the sensitivity and linear response of the output due to the resistance change of the magnetoresistive element 43, the magnetic equilibrium point was set at point 50 in FIG.
Therefore, a bias magnetic field is applied using the first conductive thin film 42.

Problems to be Solved by the Invention However, when magnetoresistive elements are formed into minute patterns as recording density increases, there is a problem in that Barkhausen noise due to discontinuous domain wall movement occurs during head output.

In other words, the magnetoresistive element in the demagnetized state has many magnetic domains, and when the signal magnetic field from the recording medium acts on the magnetoresistive element and the above-mentioned magnetic domains move discontinuously, as shown in Figure 6. This will generate Barkhausen noise.

As a result, there was a problem in that good signal reproduction could not be achieved.

Means for Solving the Problems In order to solve the above problems, the thin film magnetic head of the present invention includes a magnetoresistive element made of a ferromagnetic metal material and a signal magnetic field from a magnetic recording medium to the magnetoresistive element. It consists of a yoke for guiding, at least two electrodes for detecting changes in resistivity of the magnetoresistive element, and a coil wound around the magnetoresistive element.

Operation With the present invention configured as described above, a direct current is passed through a coil wound around a magnetoresistive element, and a direct current magnetic field generated from the coil is applied to the magnetoresistive element. Since this DC magnetic field acts to make the magnetoresistive element have a single magnetic domain structure, it is possible to prevent Barkhausen noise caused by discontinuous movement and achieve good signal reproduction.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1(a) is a plan view showing a schematic configuration of a thin film head in a first embodiment of the present invention.

In FIG. 1(a), 11 is a magnetoresistive element, 12a has a recording medium (not shown) at its lower end, and a magnetoresistive element 11 at its upper end.
a front yoke made of a soft magnetic thin film magnetically coupled with
2b has the magnetoresistive element 11 at the lower end and the ferromagnetic substrate 1 at the upper end.
The rear yoke 13a and 13b are magnetically coupled to the conductive thin film 1 for passing a sense current to the magnetoresistive element 11.
Reference numeral 4 denotes a coil made of a thin conductive film wound around the magnetoresistive element 11 and used to apply a direct current magnetic field to the magnetoresistive element 11. FIG. 1(b) is a sectional view of the coil 14 of the thin film head in this embodiment. In FIG. 1(b), the same parts as in FIG. 1(a) are given the same numbers and their explanations will be omitted. 15 is a ferromagnetic substrate.

Next, the operation will be explained.

A bias magnetic field is applied to the magnetoresistive element 11 in the same manner as in the conventional example. (Means for applying a bias magnetic field are not shown) The signal magnetic field from the recording medium is applied to the front yoke 1.
21L, the magnetoresistive element 11, and the rear yoke 12b. Further, the magnetoresistive element 11 includes conductor thin films 131L, 13
A sense current is caused to flow through the magnetoresistive element 11, and the resistance value of the magnetoresistive element 11 changes in accordance with the signal magnetic field, and by converting this resistance change into a voltage change, the signal on the recording medium can be reproduced.

At this time, a direct current is flowing through the coil centered around the magnetoresistive element 11, and this current causes the magnetoresistive element 1 to
A DC magnetic field is applied in the longitudinal direction of 1. Since this magnetic field makes the magnetoresistive element 11 a single magnetic domain, it is possible to prevent Barkhausen noise caused by discontinuous movement of the domain wall.

2(&), (1)) are a plan view and a sectional view of a thin film magnetic head showing a second embodiment of the present invention. In this figure, parts having the same structure as in FIG. 1 are given the same numbers. The difference from the configuration of the first embodiment is that a part of the coil 24 is electrically coupled to the magnetoresistive element 11. And a conductor thin film 13a.

13b is set to a negative potential and the coil 24 is set to a positive potential, and the sense current is passed from the coil 24 to the magnetoresistive element 11 and the conductor thin film 131L.
, 13b. Further, it goes without saying that, as in the first embodiment, a current necessary to make the magnetoresistive electrons 11 into a single magnetic domain flows through the coil 24.

The operation of the second embodiment is basically the same as that of the first embodiment, so a description thereof will be omitted.

Now, in the second embodiment, it is also possible to regenerate the signal magnetic field by applying a bias magnetic field from the outside as in the first embodiment, but in the second embodiment, a self-bias magnetic field is used. This allows signal reproduction with even better S/N ratio. This will be explained with reference to FIG. In FIG. 3, the same components as in FIG. 2 are given the same numbers. 318L is a first magnetoresistive element section, 31b is a second magnetoresistive element section, and 32a is a first magnetoresistive element section.
The sense current flowing through the magnetoresistive element portion 318L, 32b
is the sense current flowing through the second magnetoresistive element section 312L,
332L is a self-bias magnetic field created by the sense current 32a flowing through the first magnetoresistive element section 312L, 33b is a self-bias magnetic field created by the sense current 32b flowing through the second magnetoresistive element section 31b, 34 is the current flowing through the coil 24, 3
Reference numeral 6 denotes an amplifier section 36&, 36b which differentially amplifies the reproduction signal of the first magnetoresistive element section 31a and the reproduction signal of the second magnetoresistive element section 31b, which are resistors.

FIG. 3(1)) is a characteristic diagram showing the relationship between the magnetic field applied to the magnetoresistive element (horizontal axis) and the resistance of the magnetoresistive element (vertical axis). Next, the operation will be explained. The current 34 flowing through the coil 24 and the sense current 32J32b are determined by the shape of the magnetoresistive element (element width, element part) and the shape of the coil 25 (film thickness 1
By considering the width), it is possible to flow at an appropriate value. In particular, for the sense currents 3211 and 32b, it is possible to set a current value at which a self-bias magnetic field can be applied.

Since the sense currents 32a and 32b are flowing in opposite directions, the self-bias magnetic fields are also in opposite directions, and the self-bias magnetic fields become B, . . . B2 in FIG. 3(b). As a result, the first magnetoresistive element portion 31a due to the signal magnetic field 36
The second magnetoresistive element section 31b outputs outputs 37a and 37b, and these outputs have opposite phases. For this reason,
Differential amplification is possible at the subsequent amplifier 35, and the S/N
A reproduced signal with a good ratio can be obtained. Needless to say, the magnetic field created by the current 34 flowing through the coil 26 causes the magnetoresistive element 11 to become a single magnetic domain, thereby preventing Barkhausen noise from occurring.

In addition, in the first embodiment, the coil 14 has one turn, but it has two turns.
Similar results can be obtained even at tangents or higher.

Further, in the second embodiment, the coil 24 has one turn, but the same result can be obtained even if the coil 24 has two turns or more. However, only one location must be electrically coupled to the magnetoresistive element.

Effects of the Invention As described above, according to the present invention, by providing a coil wound around a magnetoresistive element, generation of Barkhausen noise can be prevented and a reproduced signal with a good S/N ratio can be obtained.

[Brief explanation of drawings]

FIG. 1(a) is a plan view of a thin film magnetic head according to the first embodiment of the present invention, FIG. 1fb) is a cross-sectional view of the same, and FIG.
L) is a plan view of a thin film magnetic head according to a second embodiment of the present invention, FIG. 2(b) is a sectional view thereof, and FIG. Figure 3(b) is a characteristic diagram of the magnetoresistive element, Figure 4 is a perspective view of a conventional thin film magnetic head, Figure 6 is a characteristic diagram of the magnetoresistive element, and Figure 6 is a diagram of the characteristics when Barkhausen noise is generated. FIG. 3 is a characteristic diagram of a magnetoresistive element. 11... Magnetoresistive element, 12a, 12b...
・Yoke, 13L, 13b・River・Conductor thin film, 14・
River... Koinope 15... Ferromagnetic substrate. Name of agent: Patent attorney Toshio Nakao and one other person If
---Resistance element /, 3 b /4 /4 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. Figure Nl-Doo---Bulk Hakusera Noise Unsho Qi Qta Kameko 1; Application Punmizo η Strength Procedure Amendment (
Method) % formula % 1 Indication of the case 1985 Patent Application No. 51306 2 Name of the invention Thin film magnetic head 3 Relationship with the person who corrects the case Patent application
Colonel Tokoro 1006 Oaza Kadoma, Kadoma City, Osaka Name (582) Matsushita Electric Industrial Co., Ltd. Representative Tani
Akio I 4 representatives 1 person Address: 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] a magnetoresistive element made of a ferromagnetic metal material, a yoke for guiding a signal magnetic field from a magnetic recording medium to the magnetoresistive element, and at least two electrodes for detecting a change in resistance of the magnetoresistive element; A thin film magnetic head comprising a coil wound around the magnetoresistive element.