JPS60119618A - Thin film magnetic head - Google Patents

Abstract

PURPOSE:To make Barkhausen jump noise small by covering surface of a rectangular magneto-resistance effect element with plural beltlike ferromagnetic thin films of high coercive force in parallel and oblique in longitudinal direction. CONSTITUTION:Magnetic coupling force (called ferromagnetic exchange coupling) that tends to make mutal magnetization parallel is generated at a place where a CoP electrodeposited film 12 is directly covered on a thin ''Permalloy'' film to become a composite film, and the composite film acts as a whole as a magnetic thin film of high coercive force. Consequently, magnetization of the part of composite film does not move even when a signal magnetic field is given. In a place (13 MR segment) where the thin ''Permalloy'' film exposes, the ratio d/q, where d is the width and q is the length of the segment, can be made sufficiently smaller than ''1''. By this processing, magnetic domain breakup becomes difficult in MR segment 13 and behaves as single magnetic domain. As the part of composite film between MR segment 13 and MR segment 13 becomes a hard film, each Mr segment 13, 13- acts as an independent soft film.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a thin film magnetic head that detects signals recorded on a magnetic recording medium by applying the magnetoresistive effect of a ferromagnetic thin film made of permalloy or the like.

<Prior Art> Conventionally, thin film magnetic heads that utilize the magnetoresistive effect of ferromagnetic thin films are known to have many advantages over bulk type magnetic heads that are commonly used. In other words, a thin film magnetic head receives a signal magnetic field recorded on a magnetic recording medium and extracts this as a resistance change (voltage change), so it can reproduce signals without depending on the transfer speed of the magnetic recording medium, and has a high output. It has the advantage of being

However, in this thin film magnetic head, noise and distortion in the reproduction output occur due to Barkhausen jump and hysteresis peculiar to the magnetoresistive element (permalloy film), which has become a major problem.

Now, consider a thin film magnetic head as shown in FIG.

In the figure, 1 is a magnetoresistive element made of permalloy film, 2
is a current supply lead. Further, 3 is the direction of applying the signal magnetic field, and 4 is the direction of the easy axis of magnetization of the magnetoresistive element l. The direction perpendicular to the easy axis direction 4 is the hard axis direction.

t is the track width, t is the device thickness, and W is the inside of the device. Here, t=90 pm, t=500X,
The results of measuring the resistance change rate ΔR/R while applying an external magnetic field from the signal magnetic field application direction 3 with w = 80 μm are shown in the fifth table.
As shown in the figure. Also, the magnetic domain within the element l at that time
The movement is shown in Figure 6. After applying external magnetism in FIG. 5, the external magnetic field was reduced and a magnetic domain was observed at 1120e in the same figure, as shown in FIG. 6(a). In other words, the magnetic domain was divided into four. In the figure, 5 indicates a magnetic domain, 6 indicates a magnetization vector, and 7 indicates a domain wall. That is, a multi-domain state is already exhibited at about the saturation point T in the resistance change rate curve of FIG. Each magnetic domain 5 has a buckling domain structure in which the direction of magnetization is alternately changed as shown in FIG. 6(a). Next, as shown in FIG. 5, when the external magnetic field applied to the magnetoresistive element l is decreased, the resistance value shifts from ■ to ■, a so-called Barkhausen jump occurs. This is due to the decrease in the external magnetic field.
The two magnetic domains in the center of the figure (,) merge into one, forming the Bloch line (or Bloch line) as shown in Figure 6(b).
och point) 8, the direction of magnetization on the left and right sides is reversed in the direction perpendicular to the surface, and from this state the Bloch line (or Bloch point) 8 in the same figure rapidly moves to the left as the external magnetic field decreases. This occurs due to movement. As a result of this movement, the state of the magnetic domain becomes as shown in FIG. 6(C).

As described above, the bulk jump of the magnetoresistive element is caused by the movement of the Bloch line, which occurs during the process of merging of the magnetic domains once split within the element. Noise caused by this Barkhausen jump becomes a particularly serious problem in thin-film magnetic heads for reproducing high-density magnetic recording media. This is because if the track width t is made smaller in order to increase the recording track density, there is a limit to the value of W in the element, so w/l (aspect ratio) becomes 1.
This is because magnetic domain splitting tends to occur as a result.

<Purpose> The present invention has been made in view of the above conventional points, and an object of the present invention is to provide a thin film magnetic head that can extremely reduce Barkhausen jump.

<Embodiment> An embodiment of the thin film magnetic head according to the present invention will be described in detail below with reference to the drawings. FIG. 1(,) is an external perspective view of an embodiment of a thin film magnetic head according to the present invention, and FIG.
b) shows its plan view.

In the figure, numeral 9 is a permalloy thin film (magnetoresistive element) of 81% Ni and 19% Fe, and the film thickness is 500x. 10 is a current supply lead. On the permalloy film 9 is a CoP electrodeposited film I having a coercive force of 500 to 7000 e.
2 is deposited. This film thickness is +oooX. This C
As shown in the figure, the shape of the oP electrodeposited film 12 is diagonal to the longitudinal direction of the rectangular permalloy thin film 9 (angle ψ is 3).
0° to 60°) as a striped pattern. 11 is the signal magnetic field application direction. As mentioned above, at the point where the CoP electrodeposited film 12 is directly deposited on the permalloy thin film 9 to form a composite film, a magnetic coupling force (referred to as ferromagnetic exchange coupling) that tries to make the mutual magnetization parallel is generated, and the composite film is formed. The film as a whole behaves as one high coercivity magnetic thin film.

The parts of the composite film in this example have a coercive force of 200 to 5000e.
It becomes a hard film. Therefore, even if a signal magnetic field is applied, the magnetization of the composite film does not change. Also, the shape of the exposed part +3 of the permalloy thin film 9 (hereinafter referred to as MR segment) is given by the ratio d/, where the width is d1 and the segment length is q.
q (this value corresponds to the aspect ratio) is made sufficiently smaller than 1. In this embodiment, the track width t
''; When the element width w=lo μm and the width d of the MR upper segment 3 is about 1 μm, d/q < ol, which is sufficiently smaller than l. With this treatment, the MR segment! Operates as a magnetic domain.Also, there is a composite film between the MR upper segment 3 and the MR upper segment 3, but since this composite film is a hard film, each MR upper segment 8.I3 ．．
... each operate as an independent soft membrane. Generally, in a thin-film magnetic head, the resistance change of a magnetoresistive element is proportional to the square of the inner product of its magnetization vector and sense current vector, so a bias magnetic field has been applied to obtain linear response characteristics, as is well known. . In the thin film magnetic head of the above embodiment, the MR upper segment 3°18, I
A bias magnetic field is applied to ll..., and a linear response characteristic is obtained by this bias magnetic field.

Next, two methods of magnetizing the above composite film will be explained.

FIG. 2(a) shows an explanatory diagram for explaining the first method of magnetizing the composite film. In the figure, 9 is a permalloy thin film! 2 is a CoP electrodeposited film, and 13 is a segment on MR. The composite film of permalloy thin film 9 and CoP electrodeposited film 12 is 3
A stripe shape having an angle ψ of about 0° to 60° is formed. The direction of magnetization of this composite film is the direction of arrow 14, that is, the direction parallel to the above-mentioned stripes, and magnetization is performed by applying an external magnetic field larger than the coercive force of the composite film. In addition, at this time, magnetization of B and O occurs at the tip of the composite film, and this magnetization O1 generates a magnetic field in the direction of the broken line arrow 15, and this generated magnetic field causes the MR segment)+3
There is a risk that the magnetization of the For this reason, the width of the composite membrane (Co
The width of the P electrodeposited film 12 must be made sufficiently smaller than the MR upper segment 3.

When a signal magnetic field is applied in the positive direction from the direction of the arrow 16 in the thin film magnetic head described above, the angle between the magnetization in the MR segment +3 and the sense current 17 approaches 90°, so the resistance decreases. When a signal magnetic field is applied in the negative direction, the angle between the magnetization in the MR upper segment 3 and the sense current 17 approaches 18001c, so the resistance increases. The magnetic field-resistance change curve of this thin film magnetic head is shown in FIG. 2(b).

As shown in the figure, the magnetic field-resistance change curve showed a linear response characteristic.

Further, FIG. 3(a) shows an explanatory diagram for explaining a second method of magnetizing a composite film. The structure in this figure is the same as that in FIG. 2(a). The direction of magnetization of the composite film is the direction of arrow 18, that is, the direction of the angle that is complementary to the angle ψ of the composite film (approximately 45° to 60°), and the coercive force of the composite film is determined at that angle. This is done by applying a larger external magnetic field. At this time, magnetization of ■ and O occurs in the edge portion of the composite film, and due to the magnetization ■ and O, a magnetic field indicated by the broken line arrow 19 is generated in the same direction as the magnetization direction of the composite film.
This magnetic field acts as a bias magnetic field for segment B on the MR. According to this second direction, there is no possibility that the magnetization of the MR-t segment 13 will be disturbed by the magnetic field I9 generated by the magnetization of the edge portion of the composite film.

In the thin film magnetic head described above, when a signal magnetic field is applied in the positive direction from the direction of the arrow 20, the angle between the magnetization in the MR upper segment 3 and the sense current 21 approaches 90°, so the resistance decreases. When a signal magnetic field is applied in the negative direction, the angle between the magnetization in the MR upper segment 3 and the sense current 21 approaches 180°, so the resistance increases. The magnetic field-resistance change curve of this thin film magnetic head is shown in FIG. 3(b). As shown in the figure, the magnetic field-resistance change curve showed a linear response characteristic when the signal magnetic field was near O.

In the above embodiment, the CoP electrodeposition film 12 was formed on the permalloy thin film 9, but a structure in which the CoP electrodeposition film 12 is formed under the permalloy thin film 9 may also be used.

<Effects> According to the present invention, it is possible to obtain a thin film magnetic head in which domain splitting is less likely to occur and Barkhausen jump noise is small.

[Brief explanation of the drawing]

FIG. 1(a) is an external perspective view of an embodiment of a thin film magnetic head according to the present invention, FIG. 1(b) is a plan view thereof, and FIG. 2(a)
3(b) is a graph showing the magnetic field-resistance change curve of the thin film magnetic head, and FIG. 3(a) is an explanatory diagram for explaining the first method of magnetizing the composite film. An explanatory drawing for explaining the second method of magnetization, FIG. 4(b) is a graph showing the magnetic field-resistance change curve of the thin film magnetic head, FIG. 4 is an external perspective view of the conventional thin film magnetic head, FIG. 5 is a measurement graph of the resistance change rate, and FIG. 6 is an explanatory diagram showing the movement of magnetic domains within the element. In the figure, 1: Magnetoresistive element 2: Current supply lead 3: Signal magnetic field application direction 4: Easy magnetization axis direction 5: Magnetic domain 6: Magnetization vector 7: Domain wall 8: Bloch line 9: Permalloy thin film I For supplying discharge current Signal magnetic field application direction to lead 1 +2: COP electrodeposited film +3. MR Upper Segment Attorney Patent Attorney Aihiko Fukushi (and 2 others) Jh2 Figure (0) (b) Ko 3 Figure 4e4

Claims (1)

[Claims] 1. A thin film magnetic head characterized in that a plurality of strip-shaped high coercive force ferromagnetic thin films are deposited in parallel on the surface of a rectangular magnetoresistive element in a diagonal direction with respect to its longitudinal direction.