JPH06301934A - Magnetic recording/reproducing apparatus - Google Patents

Abstract

PURPOSE:To reproduce signals well without Barkhausen noises by impressing a current to a conductor which applies a bias magnetic field to an MR effect element, then reducing the value of the current continuously and impressing a direct current. CONSTITUTION:With the sensitivity and striction of outputs of an MR head taken into consideration, the value of a direct current to be impressed to a bias conductor 5 in order to form a magnetic field achieving the maximum bias point is set to be I2. When a reproducing operation is started, a current I1 (>I2) is impressed to the conductor layer 5 for a fixed time. The current is continuously reduced to the value I2, and thereafter this stationary current I2 is impressed. A sense current is supplied from a reproducing circuit 3 to a lead layer to detect the change of tone resistance of an MR element. At this time, a signal magnetic field on a recording medium 7 enters from a gap part 9 and flows in a magnetic circuit constituted of a yoke 8, the MT element 6 and a magnetic substrate 4. The electromagnetic conversion is executed at the element 6 corresponding to the intensity of the signal magnetic field based on the change of the resistance of the element, so that the signals are read at the lead layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus having a reproducing head composed of a magnetoresistive effect element.

[0002]

2. Description of the Related Art In recent years, in the field of magnetic recording, a thin track magnetic head having a narrow track and a multi track has been required as the recording density is increased. As this thin film magnetic head, an inductive head using a coil and a reproducing MR head utilizing a magnetoresistive effect (MR effect) are known as in a bulk head.

Since the output of an inductive head using a coil is proportional to the relative speed of the tape / head,
When the relative speed is small, the output also becomes small, and good reproduction cannot be performed. On the other hand, a magnetoresistive head (hereinafter referred to as MR head) utilizing the magnetoresistive effect (MR effect) has its resistance value changed according to the magnetic flux flowing into the magnetoresistive effect element (hereinafter referred to as MR element). Since electromagnetic conversion is performed, there is an advantage that a high output can be obtained regardless of the relative speed of the tape / head.

The MR head has a sectional structure shown in FIG. That is, the bias conductor layer 42 is formed on the magnetic substrate 41 via the insulating layer, and the MR element 43 is further formed via the insulating layer. In order to apply a sense current to the MR element 43, lead layers (not shown) are formed at both ends of the MR element 43, and a yoke 45 for applying a signal magnetic field on the recording medium 44 to the MR element 43 via an insulating layer. Are formed. In the front gap portion 46 of the MR head, the gap length is regulated by the insulating layer, and in the rear gap portion 47, the yoke 45 and the magnetic substrate 41 are magnetically coupled.

The reproducing process will be described. During playback operation,
A direct current called a bias current is applied to the bias conductor layer 42. A direct current magnetic field generated by this current sets a bias point, and a signal magnetic field from the recording medium around this bias point is centered on the MR element 43 by the yoke 45. Applied to the MR element 43, the resistance of the MR element 43 changes due to this signal magnetic field, and this resistance change is extracted as a voltage change by the sense current flowing in the lead layer. The bias point is determined from the sensitivity of this voltage change and distortion.

[0006]

In the above-described conventional magnetic recording / reproducing apparatus, Barkhausen noise caused by the movement of the domain wall is generated during reproduction, and good signal reproduction is hindered. This will be explained below.

In the MR element, an easy axis of magnetization is usually formed in a direction perpendicular to the inflow direction of the signal magnetic field. At this time, the magnetization in the MR element in the absence of a bias magnetic field is oriented in a direction parallel to the easy axis of magnetization. However, as shown in FIG. 5, the magnetic domain wall 48 is generated due to the magnetic stability in the MR element 42.

When a reproducing current is applied by applying a bias current and a sense current in such a state, there is a problem that a discontinuous movement of the domain wall occurs and this becomes Barkhausen noise, which hinders good reproduction.

An object of the present invention is to solve the above problems and to provide a magnetic recording / reproducing apparatus which reproduces a good signal without Barkhausen noise.

[0010]

To achieve this object, in the magnetic recording / reproducing apparatus of the present invention, the easy axis of magnetization of the MR element is 5 to 30 with respect to the direction perpendicular to the inflow direction of the signal magnetic field flowing into the MR element. It has a tilted MR element and a bias conductor for applying a bias magnetic field to the MR element, and after applying a direct current I ₁ to the bias conductor, the current value is continuously changed to I ₂ (I ₁ > I ₂ > 0). ) Is included in the DC current circuit. The current I ₂ is a current in which the sensitivity and distortion of the output of the MR element are improved by the magnetic field generated thereby.

[0011]

According to the present invention, when the direct current I ₁ is applied, a single domain state can be formed by the above-described structure, so that no domain wall is generated in the MR element, and therefore good signal reproduction without Barkhausen noise can be performed.

[0012]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 is a block diagram of a reproducing section of a magnetic recording / reproducing apparatus according to the present invention. Reference numeral 1 is an MR head, 2 is a current circuit for applying a bias current to a bias conductor layer of the MR head 1, 3 is a reproducing circuit for applying a sense current to an MR element in the MR head 1, and a reproducing circuit for detecting a reproduction output, and 5 is a bias. The conductor layer 6 is an MR element. The heads and circuits of the recording system, the mechanism for moving the recording medium, etc. are omitted.

FIG. 2 is a sectional view of the MR head. The bias conductor layer 5 is formed on the magnetic substrate 4 via an insulating layer. The bias conductor layer 5 is connected to the current circuit 2 that applies a current to apply a bias magnetic field. Further, the MR element 6 is formed via the insulating layer. Lead layers (not shown) are formed at both ends of the MR element 6 in order to apply a sense current to the MR element 6. The lead layer is connected to the reproducing circuit 3 which detects a resistance change of the MR element 6. Then, a yoke 8 for applying a signal magnetic field on the recording medium 7 to the MR element 6 via an insulating layer is formed. M
In the front gap portion 9 of the R head, the gap length is regulated by the insulating layer, and in the rear gap portion 10, the yoke 8 and the magnetic substrate 4 are magnetically coupled.

Next, the operation during reproduction will be briefly described. First, in consideration of the sensitivity and distortion of the output of the MR head, a direct current value applied to the bias conductor layer 5 is set to I _{2 in} order to generate a magnetic field that gives an optimum bias point.

The current I ₁ to the bias conductor layer 5 at the start of the reproducing operation (> I ₂₎ is applied a predetermined time, and reduces the current value continuously to I _2, then the current value I ₂
Is constantly applied.

A sense current is applied to the lead layer from the reproducing circuit 3 in order to detect a change in resistance of the MR element.

When the current value I ₂ is constantly applied to the bias conductor layer 5, the signal magnetic field on the recording medium 7 flows from the front gap 9 of the MR head, and this signal magnetic field is applied to the yoke. 8, the MR element 6, and the magnetic substrate 4. In the MR element 6, the resistance of the MR element changes in accordance with the strength of the signal magnetic field to perform electromagnetic conversion, and the lead layer performs the reading.

Barkhausen noise is not generated by the above operation. This will be described in more detail.

FIG. 3 shows the current applied to the bias conductor layer 5 and the state of the domain wall (magnetization) in the MR element 6. 3, (a) is a relationship between the current applied to the conductor layer and time, (b) to (e) are schematic diagrams of the domain wall (magnetization direction) of the MR element 6, and FIG. A means the easy axis of magnetization, and is described in association with the time of applying the current in (a). The Y axis is the direction in which the signal magnetic field from the recording medium flows. In this embodiment, the easy axis of magnetization of the MR element is tilted +10 degrees with respect to the X axis.

First, before performing the reproducing operation, FIG.
As shown in FIG. 5, the domain wall 11 is generated in the MR element 6.

A DC current I ₁ is applied to the bias conductor layer 5 at the start of the reproducing operation, and a DC magnetic field (Hbias1) 13 generated by this causes all the magnetizations 12 in the MR element to face the Y-axis direction (see FIG. c)). The bias magnetic field (Hbias1) 13 has a magnetic field strength higher than the anisotropic magnetic field Hk of the MR element 6.

Then, the direct current applied to the bias conductor layer 5 continuously decreases until the current reaches I ₂ . At this time,
The magnetization 12 in the MR element 6 does not generate a domain wall and
It rotates clockwise as shown in (d).
Since the easy axis of magnetization of the element 6 is inclined with respect to the X axis, the angle between the magnetization 12 and the easy axis of magnetization is smaller in the clockwise direction. If they are parallel, when the direct current is reduced due to factors such as anisotropic dispersion, the magnetization in the MR element 6 has a magnetization component 14 that rotates clockwise and a magnetization component 15 that rotates counterclockwise. The domain wall 16 is generated (FIG. 3 (f)).

The current applied to the bias conductor layer 5 is I ₂
Then, the magnetization 12 in the MR element 6 becomes bias current I ₂
The bias magnetic field (Hbias2) 17 generated from the magnetic field causes the optimum bias point to be realized (FIG. 3 (e)).

When the signal magnetic field from the recording medium 7 flows into the MR element 6 in such a state, the resistance of the MR element 6 continuously changes because there is no domain wall in the MR element 6, and Barkhausen noise is generated. It does not occur and the output of the MR element 6 becomes good.

In the present embodiment, the inclination of the easy axis of the MR element 6 is set to 10 degrees, but in view of the noise suppressing effect, the reproduction output, and the magnitude of the bias current I ₁ to be applied, the easy axis is set. If the inclination is 5 to 30 degrees, the same effect is obtained.

[0027]

As described above, in the magnetic recording / reproducing apparatus according to the present invention, the MR axis having the easy axis of magnetization inclined by 5 to 30 degrees with respect to the direction perpendicular to the inflow direction of the signal magnetic flux flowing into the MR from the recording medium.
A thin film magnetic head for reproduction having a conductor for applying a bias magnetic field to the element and the MR element, and a direct current I ₁ is applied to the conductor for applying a bias magnetic field, and then the current value is continuously changed to I _2.
By having a direct current circuit for changing to (I ₁ > I ₂ > 0), a magnetic domain wall is not generated in the MR element when reproducing the recording medium, so that a good reproduction output without Barkhausen noise can be obtained. You can

[Brief description of drawings]

FIG. 1 is a block diagram of a reproducing section of a magnetic recording / reproducing apparatus of the present invention.

FIG. 2 is a sectional view of a reproducing MR head of a magnetic recording / reproducing apparatus of the present invention.

3A is a diagram showing a waveform of a bias current of the magnetic recording / reproducing apparatus of the present invention, FIG. 3B is a diagram showing a domain wall (magnetization) state of the MR element, and FIG. 3C is a domain wall (magnetization) state of the MR element. (D) shows a domain wall (magnetization) state of the MR element (e) shows a domain wall (magnetization) state of the MR element (f) shows a domain wall (magnetization) state of the MR element

FIG. 4 is a sectional view of a reproducing MR head of a conventional magnetic recording / reproducing apparatus.

FIG. 5 is a diagram showing generation of a domain wall.

[Explanation of symbols]

 1 MR head 2 Current power supply circuit 3 Reproducing circuit 4, 41 Magnetic substrate 5, 42 Bias conductor layer 6, 43 MR element 7, 44 Recording medium 8, 45 Yoke 9, 46 Front gap part 10, 47 Rear gap part 11, 16, 48 Domain wall 12, 14, 15 Magnetization 13, 17 Bias magnetic field

Claims (1)

[Claims] 1. A magnetoresistive effect element is used as an electromagnetic conversion element, and the magnetoresistive effect element is 5 to a direction perpendicular to an inflow direction of a signal magnetic flux flowing from the recording medium into the magnetoresistive effect element.
A reproducing thin-film magnetic head having a conductor that has an easy axis of magnetization inclined by 30 degrees and applies a bias magnetic field to the magnetoresistive effect element, and a current value I ₁ is applied to the conductor, and then the current value is continuously changed to I ₂ A magnetic recording / reproducing apparatus comprising a current circuit for applying a direct current reduced to (I ₁ > I ₂ > 0).