JP2559109B2 - Yoke type thin film magnetic head - Google Patents

Description

The present invention relates to a signal recorded on a magnetic recording medium using a magnetoresistive effect element (hereinafter referred to as MR element) to which the magnetoresistive effect of a ferromagnetic thin film is applied. The present invention relates to a yoke type thin film magnetic head (hereinafter referred to as a YMR head) for detecting

[Conventional technology]

FIG. 8 shows the structure of a general YMR head. The upper yokes 1 and 5 are usually made of a permalloy film having a film thickness of about 0.5 to 1.0 μm, and the signal magnetic field generated in the magnetic recording medium is
A magnetic flux introduction path for guiding to the MR element 2 is configured. The ferromagnetic films 3 and 3 are films having good conductivity and large coercive force, and are made of Co-P, Ni-Co, Ni-Co-P, or the like.
The film thickness is 1000 to 2000Å. Lead conductor part 4 ・ 4
Is made of Al-Cu film and its film thickness is 1000 ~ 2000Å
Is. Below the MR element 2, the MR element 2
Conductor 6 made of Al-Cu for applying a bias magnetic field to the
Is provided. The lower yoke 7 is made of a high-permeability magnetic material, and this high-permeability magnetic material is generally made of polycrystalline Ni.
A -Zn ferrite substrate or a single crystal or polycrystalline Nn-Zn ferrite substrate is used. The head gap 10 is 0.2 because the recording wavelength actually used is about 0.5 μm minimum.
It is set to about 0.3 μm. Further, as shown in FIG. 9, a magnetic recording medium 9 is located in the vicinity of the head gap, and a spacing 8 is formed between the magnetic recording medium 9 and the head gap 10. ing.

In the YMR head configured as described above, the MR element 2
The direction of the easy axis of magnetization at the time of making the MR element 2
It is set in the longitudinal direction of the MR element 2. The signal magnetic field generated from the magnetic recording medium 9 is detected by passing a sensor current in the longitudinal direction of the MR element 2 and extracting the change in the voltage generated across the MR element 2.
Further, a desired bias magnetic field is generated by passing a current through the conductor 6, and this is applied to the MR element 2 to move the operating point of the MR element 2 to a point having good linearity. Furthermore, the ferromagnetic films 3 and 3 and the MR element 2 are ferromagnetically exchange-coupled to each other.
A weak magnetic field is applied in the longitudinal direction of the MR element 2. And
By this weak magnetic field, the MR element 2 is brought into a single domain state, the domain wall inside the MR element 2 is eliminated, and the magnetization inside the MR element 2 is prevented from changing discontinuously, so that Barkhausen noise is generated due to the domain wall movement. It's suppressed.

[Problems to be Solved by the Invention]

However, in general, the direction of the easy axis of magnetization of the MR element 2 is MR
Not all areas of element 2 are oriented in the same direction. This is because when the MR element 2 is manufactured, or when the head gap 10 and the upper yokes 1 and 5 are formed, angular dispersion of the easy axis of magnetization tends to occur.
This is because a constant distribution is formed in the direction of the easy axis of magnetization in each region inside. Also, it is difficult to eliminate this distribution. In this way, each point a, b, on the MR element 2
It is assumed that the directions of the easy axes of magnetization in c, d, and e are in the directions of the arrows as shown in FIG. 10, and the weak magnetic field in the longitudinal direction of the MR element 2 due to the ferromagnetic film 3 is on the left side of the paper. From the right side, that is, in the direction of arrow →, the magnetization curves in the stripe width direction of the MR element 2 at the points a, b, c, d and e are shown in FIGS. ). In addition, the ΔR / R curve corresponding to the reproduction output of the MR element 2 responds to the discontinuous change in the magnetization on the MR element 2 as shown in FIG. Discontinuous jumps occur in a part of the magnetic field and Barkhausen noise caused by magnetization switching is generated. Moreover, MR
When the direction of the easy axis of magnetization is set to the longitudinal direction when the element 2 is manufactured, the distribution of the directions of the easy axis of magnetization in the MR element 2 is distributed in both positive and negative directions with respect to the longitudinal direction. . Therefore, discontinuous jumps occur on the horizontal axis of the ΔR / R curve, that is, on both the positive and negative sides of the magnetic field Ha corresponding to the signal magnetic field, and the operating point of the MR element 2 is set to a point with good linearity due to the bias magnetic field. When the moving point is moved in either positive or negative magnetic field direction, Barkhausen noise caused by magnetization switching is induced.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to prevent generation of Barkhausen noise due to domain wall movement included in a reproduction output signal, and to cause bulk switching due to magnetization switching. It is an object of the present invention to provide a yoke type thin film magnetic head capable of preventing the occurrence of Hausen noise.

[Means for solving the problem]

In order to solve the above problems, a yoke type thin film magnetic head according to the present invention includes a magnetoresistive effect element that detects a signal magnetic field generated in a magnetic recording medium as a resistance change, and a magnetic flux from a head gap to the magnetoresistive effect element. A yoke for guiding the magnetic field, a DC magnetic field applying means for applying a desired weak magnetic field in the longitudinal direction of the magnetoresistive effect element, and a conductor for applying a desired bias magnetic field in the stripe width direction of the magnetoresistive effect element. In the thin film magnetic head, the magnetoresistive effect element is made into a single magnetic domain by the DC magnetic field applying means, and its easy axis of magnetization is inclined 5 ° to 20 ° with respect to the longitudinal direction of the magnetoresistive effect element. It is characterized by that.

[Action]

Since the magnetoresistive effect element is made into a single magnetic domain by the DC magnetic field applying means, there is no domain wall. As a result, it is possible to suppress the generation of Barkhausen noise due to the domain wall movement.

Further, since the easy axis of magnetization in the magnetoresistive effect element is inclined 5 ° to 20 ° with respect to the longitudinal direction of the magnetoresistive effect element, either one of the positive side and the negative side in the magnetic field corresponding to the signal magnetic field is obtained. It is possible to move the point of discontinuity to the. Therefore, when the operating point of the magnetoresistive effect element is moved to a point having good linearity by the bias magnetic field, if the operating point on the side without the discontinuous jump in the magnetic field is moved, it is in the same direction as the bias magnetic field. It is possible to prevent the magnetization switching that occurs in the magnetic field region. Therefore, it is possible to avoid the occurrence of Barkhausen noise due to this magnetization switching.

From the above, it is possible to suppress the generation of Barkhausen noise due to domain wall movement and to avoid the generation of Barkhausen noise due to magnetization switching in the magnetoresistive effect element, and to reproduce a reproduction output signal in the yoke thin film magnetic head. Of high quality.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 9. For convenience of explanation, the eighth
FIG. 9 and FIG. 9 are used again, and the reference numerals of the members in FIG. 1 correspond to those of FIG. 8 and FIG.

The yoke type thin film magnetic head (hereinafter referred to as YMR head) according to the present invention, as shown in FIGS. 8 and 9, is a magnetoresistive effect element that detects a signal magnetic field generated in the magnetic recording medium 9 as a resistance change ( Hereinafter referred to as MR element) 2
And an upper yoke 1.5 that guides a signal magnetic flux from the head gap 10 to the MR element 2, and a DC magnetic field application for applying a desired weak magnetic field in the longitudinal direction of the MR element 2 in order to make the MR element 2 into a single magnetic domain. The ferromagnetic film 3.3 as a means and the MR element 2
And a conductor 6 for applying a desired bias magnetic field in the stripe width direction. In such YMR head, the M
The direction of the easy axis of magnetization in the R element 2 is tilted clockwise by 10 ° with respect to the longitudinal direction of the MR element 2, as shown in FIG.

In the above structure, the MR element 2 has the ferromagnetic film 3
-By 3, the weak magnetic field is applied in the direction indicated by the arrow →, that is, from the left side to the right side of the drawing. Therefore, the MR element 2 is in a single domain state and has no domain wall. As a result, it is possible to suppress the generation of Barkhausen noise that accompanies the domain wall movement inside the MR element 2.

The direction of the easy axis of magnetization in the MR element 2 is MR
As for each part of the element 2, approximately the same degree of angular dispersion occurs on both the positive and negative sides with respect to the direction of the set easy axis. Here, if this angular dispersion is about ± 10 degrees,
The direction of the easy axis of magnetization is distributed in the range of 0 to 20 ° with respect to the longitudinal direction in the entire region of the MR element 2. For example, at the point a on the MR element 2, the easy magnetization axis is inclined by about 20 ° with respect to the longitudinal direction, and at the point e, it is almost in the same direction as the longitudinal direction. Therefore, in this case, there is no region in which the direction of the easy axis of magnetization is tilted counterclockwise with respect to the longitudinal direction. MR at each point of a, b, c, d, e at this time
The magnetization curves in the element stripe width direction are shown in FIG.
~ (E), and the ΔR / R curve is shown in (f) of the same figure.
As shown in, a discontinuous jump occurs in a part of the curve only on the negative side of the magnetic field Ha. Therefore, when moving the operating point of the MR element 2 to a point with good linearity by the bias magnetic field,
If the operating point on the positive side of the magnetic field Ha is moved, the YMR
When the head reproduces the signal magnetic field, it is possible to prevent the magnetization switching that occurs in the magnetic field region in the same direction as the bias magnetic field, and as a result, it is possible to avoid the occurrence of Barkhausen noise due to the magnetization switching.

When the MR element 2 was manufactured, the direction of the easy axis of magnetization was tilted counterclockwise by 10 ° contrary to that shown in FIG. 1, and the other conditions were the same, the ΔR / R curve Discontinuity occurs on the positive side of the magnetic field Ha in Fig. 2 (f)
And have opposite results on the positive and negative sides of the magnetic field Ha. In this case, if a bias magnetic field is applied so as to move the operating point of the MR element 2 to the negative side of the magnetic field Ha, Barkhausen noise due to magnetization switching will not be included in the reproduction output signal.

From the above, it is possible to avoid the generation of Barkhausen noise due to domain wall movement in the MR element 2 and the generation of Barkhausen noise due to magnetization switching, and the reproduction output signal of the yoke thin film magnetic head is high. It enables quality improvement.

Next, how to determine the tilt angle (hereinafter referred to as an anisotropic tilt angle) of the easy axis of magnetization with respect to the longitudinal direction when the MR element 2 is manufactured will be described below.

The MR element 2 in the YMR head responds to the signal magnetic field in a state where the demagnetizing field is small due to the magnetic coupling of the upper yokes 1 and 5 and the lower yoke 7. Further, due to the weak magnetic field applied to the MR element 2 by the ferromagnetic film 3 having a large coercive force, the MR element 2 is in a single domain state. Third from these points
With a simple single domain model as shown in the figure, an appropriate value of the anisotropic tilt angle can be estimated. Anisotropic inclination angle θ in Figure 3, H _E is the weak magnetic field applied to the MR element 2 of a ferromagnetic film 3, M _S is the saturation magnetization of the MR element 2, Ha is an external magnetic field corresponding to the signal magnetic field is there. Prototype here
Based on the characteristics of the MR element, _HE = 1.3 [o _e ] and M _s = 796 [emu /
cc], as _{H K = 4 [o e]} , the sum of the magnetostatic energy of the anisotropic energy, magnetization M and H _E magnetization M, and the magnetization M
When the rotation angle ψ of the magnetization M with respect to Ha is calculated so that the sum of the magnetostatic energies of H and Ha is minimized, and the magnetization curve and ΔR / R curve in the χ direction (shown in FIG. 3) are obtained, Four
It becomes like each figure (a) (b) of FIGS. As shown in FIGS. 6A and 6B, when the anisotropic tilt angle θ is about 20 °, magnetization switching occurs. Further, as shown in FIGS. 7 (a) and 7 (b), when the anisotropic tilt angle θ is about 25 °, not only switching of magnetization occurs on both the positive and negative sides of Ha, but also the hysteresis of the magnetization curve. Occurs. Further, when H _E = 0.8 [o _e ] and other conditions are the same and the same calculation is performed, magnetization switching occurs on the positive side of Ha when the anisotropic inclination angle θ is about 12 °. further,
It has been confirmed that as the anisotropic tilt angle θ increases, magnetization switching occurs on both the positive and negative sides of Ha and hysteresis occurs in the magnetization curve. Thus, anisotropic inclination angle θ is the magnetic characteristics of magnitude and MR element 2 H _E, it exceeds the certain value, resulting switching magnetization on opposite sides of Ha, induces Barkhausen noise Like On the other hand, considering the anisotropic tilt angle θ in a range in which magnetization switching does not occur on both positive and negative sides of Ha, it is represented by the tangential tilt at each point in the sensitivity ΔR / R curve of the MR element 2) It has been found that it decreases as the anisotropic tilt angle θ increases. With reference to these calculation results and considering that the magnetic characteristics of the MR element 2 and the angular dispersion of the easy axis of magnetization are about 5 ° to 10 °, the inclination of the easy axis of the MR element 2 is It is suitable to set in the range of 5 ° to 20 °.

[Effects of the Invention] As described above, the yoke type thin-film magnetic head according to the present invention includes a magnetoresistive effect element for detecting a signal magnetic field generated in a magnetic recording medium as a resistance change, and a head gap to A yoke for guiding a magnetic flux, a DC magnetic field applying means for applying a desired weak magnetic field in the longitudinal direction of the magnetoresistive effect element, and a conductor for applying a desired bias magnetic field in the stripe width direction of the magnetoresistive effect element are provided. In the yoke type thin film magnetic head, the magnetoresistive effect element is made into a single magnetic domain by the DC magnetic field applying means, and its easy axis of magnetization is tilted by 5 ° to 20 ° with respect to the longitudinal direction of the magnetoresistive effect element. It is a composition.

As a result, the domain wall does not exist inside the magnetoresistive effect element, so that it is possible to suppress Barkhausen noise due to the domain wall movement. Further, it is possible to move the discontinuity generating point to either one of the positive and negative sides of the magnetic field corresponding to the signal magnetic field. Therefore, when the operating point of the magnetoresistive effect element is moved to a point having good linearity by the bias magnetic field, if the operating point on the side without the discontinuous jump in the magnetic field is moved, it is in the same direction as the bias magnetic field. It is possible to prevent the magnetization switching that occurs in the magnetic field region, and it is possible to avoid the generation of Barkhausen noise due to this magnetization switching.

Therefore, it is possible to suppress the generation of Barkhausen noise due to the movement of the domain wall in the magnetoresistive element and to avoid the generation of Barkhausen noise due to the magnetization switching. This has the effect of improving the quality.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, and is an explanatory view showing the distribution of the easy axis of magnetization when the anisotropic tilt angle θ of the easy axis of the magnetoresistive effect element is set to 10 °. 2 (a) to 2 (e) are points a in FIG. 1, respectively.
Magnetization curves in the stripe width direction of the magnetoresistive effect element in to e, (f) is a ΔR / R curve diagram corresponding to the reproducing main force of the magnetoresistive effect element, and FIG. 3 is a conceptual diagram showing a uniaxial model, Each of FIGS. 4 to 7 (a) is a magnetization curve diagram when the anisotropic tilt angle θ is 0 °, 10 °, 20 °, 25 °, and each of FIGS. 4 to 7 (B) is the anisotropic tilt angle θ
ΔR / R curve diagram when 0 °, 10 °, 20 °, 25 °, FIG. 8 is a perspective view showing the structure of a general yoke type thin film magnetic head, and FIG. 9 is a general yoke type thin film magnetic head. Top view showing the
FIG. 10 is an explanatory view showing a conventional example, FIGS. 11 (a) to (e) are magnetization curve diagrams in the stripe width direction of the magnetoresistive effect element at points a to e in FIG. 10, respectively, and FIG. FIG. 4 is a ΔR / R curve diagram corresponding to the reproduction output of the magnetoresistive effect element. 1 and 5 are upper yokes, 2 is a magnetoresistive effect element (MR element), 3 is a ferromagnetic film (DC magnetic field applying means), 4 is a lead conductor portion, 6 is a conductor, 7 is a lower yoke, and 8 is a spacing. , 9 are magnetic recording media, and 10 is a head gap.

Claims (1)

(57) [Claims] 1. A magnetoresistive effect element for detecting a signal magnetic field generated in a magnetic recording medium as a resistance change, a yoke for guiding a magnetic flux from a head gap to the magnetoresistive effect element, and a desired one in the longitudinal direction of the magnetoresistive effect element. In a yoke type thin film magnetic head comprising a DC magnetic field applying means for applying a weak magnetic field and a conductor for applying a desired bias magnetic field in the stripe width direction of the magnetoresistive effect element. A Roke type thin film magnetic head characterized in that it is made into a single magnetic domain by a magnetic field applying means, and its easy axis of magnetization is inclined by 5 ° to 20 ° with respect to the longitudinal direction of the magnetoresistive effect element.