JP2001243608A - Yoke type magnetoresistive head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a yoke type magnetoresistive head having excellent repro ducing efficiency. SOLUTION: In the yoke type magnetoresistive head 1 having a magnetic gap 7 between an upper yoke 8 and a pair of lower yokes 5A and 5B and a magnetic circuit constituted of at least the pair of lower yokes 5A and 5B having a prescribed gap G, the upper yoke 8 and a magnetoresistive element 3 provided at the position corresponding to the yoke gap G, when the length of the magnetoresistive element 3 and the length of each end part overlapping the pair of lower yokes of the magnetoresistive element 3 are L and d, respectively, the relational formula 0.1×L<=d<=0.3×L is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a yoke type magnetoresistive head used in a reproducing apparatus for a magnetic tape or the like.

[0002]

^2. Description of the Related Art In recent years, the density of magnetic recording / reproducing devices in hard disks and the like has been increased, and recording densities of ² to 6 Gbit / in ² have been put to practical use. In order to achieve such a high density, it is necessary to employ a magnetoresistive head for directly detecting magnetic flux of a recording medium instead of a conventional inductive head as a reproducing head. A giant magnetoresistive head with a spin valve as the center has been studied. By the way, when a magnetoresistive head is used for recording / reproducing a magnetic tape, a shield type magnetoresistive head in which the magnetoresistive element is exposed on the surface of the magnetic head because the magnetic head and the magnetic tape come into contact with each other and slides. There was a problem with reliability. Therefore, in order to avoid this problem, a yoke (magnetic flux guide) using a soft magnetic film
A yoke-type magnetoresistive head having the following features has been developed.

Hereinafter, a conventional yoke type magnetoresistive head will be described with reference to FIG. 5A and 5B show a conventional yoke type magnetoresistive head, and FIG.
(B) is a plan view showing the relationship between the magnetoresistive element and the lower yoke viewed from the MM side in (A) when the insulating layer 4 is not provided.
Hereinafter, the configuration of the conventional yoke type magnetoresistive head 1 will be described. As shown in FIG. 5A, an insulating layer 4 is formed on a non-magnetic substrate 2, and a rectangular magneto-resistive element 3 is formed in the insulating layer 4 and a distance t is set upward from the magneto-resistive element 3. And a lower yoke 5 composed of a front lower yoke 5A and a rear lower yoke 5B formed with a yoke gap G at a position apart from the front yoke 5A. An intermediate core 6 composed of a partial intermediate yoke 6A and a rear intermediate yoke 6B is embedded and sequentially formed. FIG. 5B
As shown in the figure, the length of the magnetoresistive element 3 is L and the width is D.
The overlap length between the lower front yoke 5A and the rear lower yoke 5B and both ends of the magnetoresistive element 3 is d.
It is.

An opening Q is formed in the insulating layer 4 corresponding to the rear intermediate core 6B, and the upper yoke 8 comes into contact with the rear intermediate core 6B through the opening Q and is formed on the insulating layer 4. Is formed. At this time, the insulating layer 4 between the front intermediate core 6A and the upper yoke 8 becomes the magnetic gap 7.
The magnetic gap 7 side is the sliding surface S of the magnetic recording medium.
Becomes As a material of the non-magnetic substrate 2, for example, Al ₂
There is O ₃ TiC, and as a material for the upper yoke 8, the lower yoke 5, and the intermediate yoke 6, for example, there is a soft magnetic film such as a CoZrNb amorphous alloy or NiFe. The material of the insulating layer 4 is Al ₂ O ₃ . Further, the intermediate core 6, the lower yoke 5, the magnetoresistive element 3, and the upper yoke 8 constitute a magnetic circuit. Actually, the magnetoresistive effect element 3 is composed of a multilayer film in which a base film, a free layer, a separation film made of Cu, a pin layer, an antiferromagnetic film, and a protective film are laminated.
A hard film for controlling the magnetic domain of the free layer and an electrode for supplying a sense current are formed to be connected to the magnetoresistive effect element 3, but are omitted in FIG.

In reading a signal from the magnetic recording medium, a signal magnetic field is supplied from the magnetic recording medium through the magnetic gap 7 while a sense current is flowing through the magnetoresistive element 3 so that the resistance change of the magnetoresistive element 3 This is performed by taking out as a product of the sense current, that is, a voltage change.

[0006]

However, the lower yoke 5 and the magnetoresistive element 3 are insulated by the insulating layer 4 so that the sense current flowing to the magnetoresistive element 3 does not flow to the lower yoke 5. Therefore, the magnetic resistance increases during this period, and the reproduction efficiency is reduced. In particular, in the case of a giant magnetoresistive head, since each magnetic layer becomes as thin as 10 nm or less, it is necessary to minimize a decrease in reproduction efficiency. As a countermeasure against this, JP-A-11-120
No. 523 discloses that the overlap length between the front and rear portions of the yoke and the magnetoresistive element is preferably set to 0 to 2 μm.

However, since the reproduction efficiency is related to the distribution of the magnetic flux density in the magnetoresistive element, it is not possible to sufficiently improve the reproduction efficiency only by specifying the overlap length. SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a yoke type magnetoresistive head having good reproduction efficiency.

[0008]

The yoke type magnetoresistive head of the present invention comprises at least a pair of lower yokes having a predetermined yoke gap, an upper yoke, and a magnetoresistive element provided in the yoke gap. And a magnetic circuit is formed, and a yoke type magnetoresistive head having a magnetic gap between the upper yoke and the pair of lower yokes, wherein the length of the magnetoresistive element is L, When the length at which both ends overlap with the pair of lower yokes is d, 0.1 × L ≦
It is characterized by satisfying a relationship of d ≦ 0.3 × L.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A yoke type magnetoresistive head according to an embodiment of the present invention will be described below with reference to FIGS. The same reference numerals are given to the same configurations as the conventional example,
The description is omitted. In the yoke type magnetoresistive head of the present invention, the length at which both ends of the magnetoresistive element 3 in the conventional yoke type magnetoresistive head 1 overlap the lower front yoke 5A and the lower rear yoke 5B is d. Then, the relationship of 0.1 × L ≦ d ≦ 0.3 × L is satisfied, and the other configuration is the same.

Next, in order to examine the reproduction efficiency of the yoke type magnetoresistive head 1 of the present invention, the magnetoresistive element 3 is made only of a free layer, and a permanent magnet is arranged near the magnetic cap 7 to generate a magnetic field. The magnetic flux density in the magnetoresistance effect element 3 was simulated using magnetic field analysis software (Maxwell 3D manufactured by Ansoft). Here, the magnetic permeability of the lower yoke 5, the upper yoke 8, and the intermediate yoke 6 is 1,000, the magnetic permeability of the free layer is 600, the distance t is 0.1 μm, and the thickness of the free layer is 6 μm. The overlap width d of the magnetoresistive element 3 and the front lower yoke 5A and the rear lower yoke 5B are the same.

First, the length L of the magnetoresistive element 3
Is fixed to 2 μm and the width D is fixed to 16 μm.
Was changed in the range of 0.5 μm to 1.5 μm, and the relationship between the position in the magnetoresistance effect element 3 and the magnetic flux density was examined. At this time, the magnetic flux density is a value measured at a position from one end C of the magnetoresistive element 3 on the sliding surface S side as a reference. The result is shown in FIG. FIG. 1 is a diagram showing the relationship between the position in the magnetoresistive element and the magnetic flux density when the yoke gap is changed. In each case where the yoke gap G was changed in the range of 0.5 μm to 1.5 μm, the magnetic flux density was changed in the central portion of the magnetoresistive effect element 3, that is, 1 μm.
It has a maximum at μm and shows a tendency to decrease at the left and right of this central part. The left and right sides of the center of the magnetoresistive element 3 correspond to the overlapping portion of the magnetoresistive element 3 and the lower yoke 5. For example, when the yoke gap G is 0.5 μm
In the case of m, the overlapping portion between the magnetoresistive element 3 and the lower yoke 5 is 0.75 μm. It can be seen that in this portion, the magnetic flux density tends to decrease.

Next, the width D of the magnetoresistive element 3 is set to 16 μm.
m and the length L is 1, 2, and 3 μm, and the yoke gap G is changed in each case.
The maximum magnetic flux density _Bmax and the average magnetic flux density _{Bavg in the above} were examined. When the length L of the magnetoresistive element 3 is 1 μm, the yoke gap G is in the range of 0.2 μm to 1.2 μm, and when it is 2 μm, the yoke gap G is in the range of 0.5 μm to 2.5 μm. In this case, the thickness was changed in the range of 0.6 μm to 3.5 μm. The results are shown in FIGS. FIG.
FIG. 4 is a diagram showing a relative magnetic flux density in the yoke gap G and the magnetoresistive element when the length L of the magnetoresistive element is 1 μm. FIG. 3 shows that the length L of the magnetoresistance effect element is 2
It is a figure which shows the yoke gap G in the case of micrometers, and the relative magnetic flux density in a magnetoresistive effect element. FIG. 4 is a diagram illustrating the relative magnetic flux density in the yoke gap G and the magnetoresistive element when the length L of the magnetoresistive element is 3 μm.

In FIG. 2, the yoke gap G is 0.2 μm.
m, the relative value is based on the maximum magnetic flux density B _max and the average magnetic flux density B _avg . In FIG.
Is a relative value based on the maximum magnetic flux density B _max and the average magnetic flux density B _avg when the magnetic flux density is 0.5 μm. In FIG. 4, the maximum magnetic flux density B _max and the average magnetic flux when the yoke gap G is 0.6 μm. This is a relative value based on the density B _avg . In FIG. 2, when the yoke gap G is 1 μm or more, in FIG. 3, when the yoke gap G is 2 μm or more,
When the yoke gap G is 3 μm or more, it indicates that the lower yoke 5 is separated from the magnetoresistive element 3 and does not overlap. As described above, the maximum magnetic flux density B _max is
Since the value is at the center of the length L of the magnetoresistive element 3,
When the length L is 1 μm, 2 μm, and 3 μm, the values are at the positions of 0.5 μm, 1 μm, and 1.5 μm, respectively.

The average magnetic flux density B _avg is the average value of the magnetic flux density in the direction of the length L of the magnetoresistive effect element 3,
This corresponds to the reproduction output of the yoke type magnetoresistive head 1.
As shown in FIGS. 2 and 3, the maximum magnetic flux density B _max tends to decrease as the yoke gap G increases as the length L of the magnetoresistive element 3 becomes 1, 2, or 3 μm. This is probably because the magnetic resistance at the yoke gap G increases and the magnetic flux density passing through the magnetoresistive element 3 decreases. Further, when the length of the magnetoresistive element 3 in FIG. 2 of 1 [mu] m, the maximum magnetic flux density B _{ma x} that low below the yoke gap G is 0.4μm, the front magnetic resistance of the yoke gap portion G decreases Subordinate yoke 5A
It is considered that a short circuit is likely to occur between the lower yoke 5B and the lower lower yoke 5B.

On the other hand, when the length L of the magnetoresistive element 3 is 1 μm, 2 μm, and 3 μm, the average magnetic flux density B _avg is 0.6 μm,
The curve becomes an upwardly convex curve which is maximum at 1.2 μm and 1.8 μm, and the decreasing slope of the portion longer than these positions is smaller than the maximum magnetic flux density _Bmax . This is because the average magnetic flux density B _avg is an average value in the magnetoresistive element 3, and the magnetic flux density decreases in the overlapping portion between the lower yoke 5 and the magnetoresistive element 3 as described in the conventional example. This seems to be due to the tendency.

2 to 4, when the length L of the magnetoresistive element 3 is 1 μm, 2 μm, and 3 μm, the yoke gap G at which the average magnetic flux density B _avg becomes maximum is equal to that of the magnetoresistive element 3. This is 60% of the length L. Typically,
If reduction within 1dB than the maximum magnetic flux density B _max,
It is used without any problem as a sufficient practical range. The length range of the yoke gap G for realizing this occurs within a range where the lower yoke 5 and the magnetoresistive element 3 overlap,
When the length L of the magnetoresistive element is 1 μm, 0.4
0.8 μm when μm to 0.8 μm and L = 2 μm
1.6 μm, 1.2 μm when L = 3 μm
2.4 μm.

In other words, in the relationship between the length L of the magnetoresistive element and the overlap length d, the range of the overlap length d is 0.1 μm to 0.3 μm when L = 1 μm.
m, L = 2 μm, 0.2 μm to 0.6 μm,
When L = 3 μm, it is 0.3 μm to 0.9 μm. Generalizing this relationship, for a base of overlap length d to decrease within 1dB than the maximum magnetic flux density B _max in the case of L = 1 [mu] m, the ones the overlap length d and L times. That is, as described above, overlap length d to decrease within 1dB than the maximum magnetic flux density B _max in the case of L = 1 [mu] m, because in the range of 0.1μm~0.3μm, 0.1 × L ≦ d ≦ 0.3 × L. When the overlap length d satisfies this condition, it is possible to obtain the yoke type magnetoresistive head 1 having good reproduction efficiency.

[0018]

According to the yoke type magnetoresistive head of the present invention, the length of the magnetoresistive element is L, and the length of both ends of the magnetoresistive element overlapping the pair of lower yokes is d. When 0.1 × L ≦ d ≦ 0.3 × L
Is satisfied, it is possible to obtain a yoke type magnetoresistive effect head having good reproduction efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a position in a magnetoresistive element and a magnetic flux density when a yoke gap is changed.

FIG. 2 is a diagram showing a yoke gap G and a relative magnetic flux density in the magnetoresistive element when the length L of the magnetoresistive element is 1 μm.

FIG. 3 is a diagram showing a yoke gap G and a relative magnetic flux density in the magnetoresistive element when the length L of the magnetoresistive element is 2 μm.

FIG. 4 is a diagram showing a relative magnetic flux density in the yoke gap G and the magnetoresistive element when the length L of the magnetoresistive element is 3 μm.

FIG. 5 shows a conventional yoke type magnetoresistive head;
(A) is a cross-sectional view, and (B) is a plan view showing the relationship between the magnetoresistive element and the lower yoke as viewed from the MM side when there is no insulating layer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Yoke type magnetoresistive head, 2 ... Nonmagnetic substrate, 3
... Magnetoresistance effect element, 4 ... Insulating layer, 5 ... Lower yoke, 5A
... front lower yoke, 5B ... rear lower yoke, 6 ... middle yoke, 6A ... front middle yoke, 6B ... rear middle yoke, 7
... magnetic gap, 8 ... upper yoke, G ... yoke gap,
L: length of the magnetoresistive element, d: overlap length,
D ... width

Claims (1)

[Claims] A magnetic circuit comprising at least a pair of lower yokes having a predetermined yoke gap, an upper yoke, and a magnetoresistive element provided at a position corresponding to the yoke gap; A yoke type magnetoresistive head having a magnetic gap between the pair of lower yokes, wherein the length of the magnetoresistive element is L, and both ends of the magnetoresistive element overlap the lower yoke. When both lengths are d, 0.1 × L ≦ d ≦ 0.3 ×
A yoke-type magnetoresistive effect head characterized by satisfying a relationship of L.