JPH05189707A - Sense current control method for magnetic head and magnetic storage device - Google Patents

Abstract

PURPOSE:To reduce a fear of breaking of a wire in an MR element due to a sense current. CONSTITUTION:When CSS operation is performed by a magnetic head 10 having the MR element 11 to a magnetic disk 20 having a recording layer consisting of a metal film, this MR element is supplied with the sense current so far as the magnetic head 10 is floating. Whether the magnetic head 10 is floated or not is detected by revolving speed of the magnetic disk 20. Consequently, an overcurrent is not conducted in the MR element due to contact between the magnetic head and the magnetic disk, and hence the wire of the MR element is hardly broken due to the sense current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a sense current of a magnetic head using a magnetoresistive effect element (hereinafter referred to as an MR element) and a magnetic memory device using the method.

[0002]

2. Description of the Related Art In a magnetic storage device using a hard magnetic disk having a magnetic film formed on a metal disk, a positive pressure type slider is generally used for a magnetic head. When a positive pressure type slider is used, the magnetic head is a so-called CSS (Contact Star).
t Stop) Perform the operation. In the CSS operation, when the magnetic disk is stationary, the slider is brought into contact with the surface of the hard disk by a spring or the like, and when the magnetic disk starts to rotate, the air flow generated between the slider and the surface of the hard disk causes the slider to become magnetic. It is levitated from the surface of the disk and stops during steady rotation at a position where its buoyancy and the pressing force of a spring or the like are in equilibrium. When the hard disk stops rotating, the pressing force causes the slider to come into contact with the surface of the magnetic disk again.

When a negative pressure type slider is used as the magnetic head, the magnetic head does not contact the surface of the magnetic disk at the time of starting and stopping, so that the magnetic head always operates in a floating state.

A hard magnetic disk is usually fixed to a spindle and is rotated at a high speed by a motor. The spindle is usually grounded to reduce noise and static.

[0005]

By the way, when a magnetic storage device is constructed by combining a magnetic head whose MR element is exposed on a sliding surface and a hard magnetic disk using a metal film as a recording layer, a CSS operation is performed. Then, when the magnetic disk is stationary and the rotational speed of the magnetic disk is low, contact between the magnetic head and the magnetic disk causes MR
There is a possibility of electrical conduction between the element and the metal film. This is because a magnetic disk using a metal film as a recording layer has a protective film adhered on the metal film, but since this protective film is extremely thin (several tens of nm), the MR element is used for reproduction when contacted. When the sense current is supplied, dielectric breakdown occurs between the MR element and the metal film, and the spindle to which the magnetic disk is fixed is grounded.

Further, even when the magnetic disk is rotating steadily, if the flying height of the magnetic head is reduced (for example, 1 μm or less), the magnetic head may collide with minute projections remaining on the surface of the magnetic disk or from the outside. The magnetic head may come into contact with the magnetic disk due to the applied shock, and even in those cases, there is a possibility of electrical conduction between the MR element and the metal film.

When a negative pressure type slider is used as the magnetic head, the magnetic head always floats above the surface of the magnetic disk. Therefore, the magnetic head does not come into contact with the magnetic disk in a normal operating state. The magnetic head and the magnetic disk may come into contact with each other due to the protrusions remaining on the disk and the impact applied from the outside. Therefore, even in the case of the negative pressure type slider, there is a possibility that electrical conduction will occur between the MR element and the metal film.

If a sense current for signal detection is supplied to the MR element when the MR element and the metal film are electrically connected to each other due to the above-mentioned causes, an excessive current flows in the MR element,
As a result, there is a problem that the MR element is disconnected.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic head sense current control method and a magnetic storage device capable of reducing the risk of MR element disconnection due to the sense current.

[0010]

[Means for Solving the Problems]

(1) In the first magnetic head sense current control method of the present invention, when the magnetic head having the magnetoresistive effect element performs the CSS operation on the magnetic disk having the recording layer made of a metal film, at the start time. , Supplying a sense current to the magnetoresistive effect element after the magnetic head has floated above the surface of the magnetic disk, and at the time of stop, supplying a sense current before the magnetic head contacts the surface of the magnetic disk. It is characterized by stopping.

In this magnetic head sense current control method, when the magnetic head contacts the surface of the magnetic disk while levitating from the surface of the magnetic disk,
It is preferable to temporarily stop the supply of the sense current at the time of contact.

(2) In the second method of controlling the sense current of the magnetic head according to the present invention, information is recorded in a state where the magnetic head having the magnetoresistive effect element floats above the surface of the magnetic disk having the recording layer made of a metal film. When recording / reproducing, when the magnetic head comes into contact with the surface of the magnetic disk, supply of the sense current is temporarily stopped at the time of contact.

(3) The first magnetic storage device of the present invention is
In a magnetic storage device in which a magnetic head having a magnetoresistive effect element performs a CSS operation on a magnetic disk having a recording layer made of a metal film, it is detected whether or not the magnetic head is above the surface of the magnetic disk. Floating detection means, sense current supply means for supplying a sense current to the magnetoresistive effect element, and sense current supply to the magnetoresistive effect element while the magnetic head is floating. And a sense current control means for controlling the sense current supply means so as to stop the supply of the sense current while the magnetic head is not flying.

This magnetic storage device is provided with a contact detecting means for detecting the contact of the magnetic head with the surface of the magnetic disk, and the contact detecting means detects the contact while the magnetic head is floating. It is preferable to control the sense current control means so that the supply of the sense current is temporarily stopped when the contact is made.

(4) A second magnetic memory device according to the present invention is
In a magnetic memory device for recording / reproducing information in a state where a magnetic head having a magnetoresistive effect element floats above the surface of a magnetic disk having a recording layer made of a metal film, a sense current When the contact is detected by the contact detecting means for detecting the contact of the sense current supplying means for supplying the magnetic head with the surface of the magnetic disk, the supply of the sense current is temporarily stopped when the contact is made. And a sense current control means for controlling the sense current supply means.

(5) In the first and second magnetic memory devices, it is preferable that the magnetoresistive effect element is exposed on the sliding surface of the magnetic head.

[0017]

In the first magnetic head sense current control method and magnetic storage device of the present invention, the sense current is supplied while the magnetic head performing the CSS operation is floating above the surface of the magnetic disk. Therefore, there is almost no possibility that the MR element will be disconnected due to an excessive current flowing between the MR element and the metal film due to the contact between the magnetic head and the magnetic disk.

In the second method of controlling the sense current of the magnetic head and the magnetic storage device of the present invention, when the magnetic head for recording / reproducing information in the floating state contacts the magnetic disk, the sense current is temporarily supplied at the time of contact. Stop. Therefore, there is no possibility that the MR element will be disconnected due to the contact in the floating state.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

[First Embodiment] FIG. 1 is a block diagram showing the configuration of a first embodiment of a magnetic memory device of the present invention. The magnetic storage device 1 of the present invention supplies a magnetic head 10 incorporating an MR element, a hard magnetic disk 20 having a metal film recording layer, a rotary drive device 30 for rotationally driving the magnetic disk 20, and a magnetic head 10. And a sense current control device 40 for controlling the sense current. The magnetic head 10 performs a CSS operation on the magnetic disk 20.

The magnetic sensing portion of the magnetic head 10 is, as shown in FIG. 2, an MR element 1 made of a permalloy film having a thickness of 15 nm.
1 and a shunt film 12 are laminated, and a pair of shield films 13 and 1 are provided on both sides of the magnetic sensitive portion with an insulating layer interposed therebetween.
4 are formed. MR element 11, shunt film 12,
The pair of shield films 13 and 14 are incorporated in the slider 15. The MR element 11 has a height of 2 μm, and its tip is exposed on the sliding surface 16 of the slider 15. Since the final polishing of the sliding surface of the magnetic head 10 is performed on a tin surface plate using a diamond paste having a grain size of 0.1 μm, it is slid on the tip of the MR element 11 after polishing. The level difference with the moving surface 16 is 5 nm or less, which is extremely small.

The magnetic disk 20 has a disk shape with a diameter of 3.5 inches. As shown in FIG. 3, a CoCrT film having a thickness of 30 nm is formed on a NiP substrate 21 via a Cr underlayer 22.
The recording layer 23 of a is formed. A carbon protective layer 24 having a thickness of 10 nm is formed on the recording layer 23. The magnetic disk 20 is fixed to the spindle 31 via an aluminum fixture 33. The spindle 31 is rotationally driven by a motor 32. Also,
The spindle 31 is grounded via a conductor 34,
The potential is always zero.

The rotation driving means 30 is composed of a motor 32. The motor 32 rotates the spindle 31, which causes the magnetic disk 20 to rotate.

The sense current control device 40 includes a rotation speed detection circuit 41 for detecting the rotation speed of the motor 32, and the MR element 11.
A sense current control circuit 42 that controls the supply / stop of the sense current to the MR element 11 and a sense current supply circuit 43 that supplies the sense current to the MR element 11.

The rotation speed detection circuit 41 monitors the rotation speed of the motor 32, and if the rotation speed exceeds a preset value, continues to send a signal to that effect to the sense current control circuit 42. If the number of revolutions does not exceed the preset value, no signal is sent to the sense current control circuit 42.

When the sense current control circuit 42 receives the signal from the rotation speed detection circuit 41, the sense current control circuit 42 sends a control signal to the sense current supply circuit 43 so as to supply the sense current to the magnetic head 10. When the signal is not sent from the rotation speed detection circuit 41, the control signal is not sent.

The sense current supply circuit 43 responds to the control signal from the sense current control circuit 42 by the M of the magnetic head 10.
A sense current is supplied to the R element 11. When the control signal is not sent from the sense current control circuit 42, the sense current is not supplied.

In this first embodiment, the rotation speed detection circuit 41
Represents the flying height detection means, the sense current control circuit 42 constitutes the sense current control means, and the sense current supply circuit 43 constitutes the sense current supply means.

In the magnetic storage device 1 having the above-described structure, the rotation speed detection circuit 41 operates as the sense current control circuit 42 until the motor 32 reaches the preset rotation speed, that is, until the magnetic head 10 completely floats. Do not send input signal to. Therefore, since the sense current is not supplied from the sense current supply circuit 43 to the magnetic head 10, the magnetic head 1
Even when 0 comes into contact with the magnetic disk 20, the MR element 11 and the recording layer 23 do not cause dielectric breakdown.

When the motor 32 reaches a preset rotation speed, the rotation speed detection circuit 41 starts to send a signal to the sense current control circuit 42. Therefore, the sense current control circuit 42 receiving the signal changes the sense current supply circuit 42. A control signal for supplying the sense current is sent to 43. Sense current supply circuit 43
Is the MR element 1 of the magnetic head 10 according to the control signal.
Supply a sense current to 1. Thus, the magnetic disk 2
The information stored in 0 is reproduced.

When the operation is stopped after the steady operation, the supply of the sense current is stopped when the number of rotations of the motor 32 is reduced to the set value as in the case of starting the operation. Therefore, also in that case, the MR element 11 and the recording layer 23 do not cause dielectric breakdown.

As described above, in the magnetic storage device 1, even if the CSS operation is repeated using the metal recording film 23 and the MR element 11, an excessive current flows into the MR element 11 and the MR element 11 is disconnected. There is no effect.

The rotation speed of the motor 32 at which the rotation speed detection circuit 41 starts to send a signal may be arbitrarily set to a value such that the magnetic head 10 completely floats above the magnetic disk 20 when the rotation speed is reached.

In this embodiment, the rotation speed detection circuit 41 is used as the flying height detection means, but any other structure may be used as long as it can detect the flying height of the magnetic head 10.

[Confirmation Test] The magnetic storage device 1 having the above-described structure was manufactured and tested to confirm the effects of the present invention. The test conditions are as follows.

Spindle 31 or magnetic disk 20
The constant rotation speed of was set to 3600 rpm. When the rotation speed of the spindle 31 reaches 3000 rpm, the rotation speed detection circuit 41 starts to send a signal to the sense current control circuit 42, and in response to this, the sense current control circuit 42 immediately sends a sense current to the sense current detection circuit 43. It was set to send a control signal to supply. Therefore, at both the start and stop, the spindle 31
If the rotation speed of the spindle 31 is 3000 rpm or more, the sense current is supplied from the sense current supply circuit 43 to the MR element 11 of the magnetic head 10, and the rotation speed of the spindle 31 is 3000 r.
When it is less than pm, the sense current is not supplied. The flying height of the magnetic head 10 was set to 0.06 μm and the sense current supplied to the MR element 11 was set to 12 mA when the spindle 31 was rotating at 3600 rpm.

The CSS operation was repeated under the above test conditions to check whether or not the MR element 11 was broken.

As a comparative example, a magnetic memory device having the same structure as the magnetic memory device 1 except that the sense current control circuit 42 is not provided was manufactured. Then, while continuously supplying the sense current to the MR element including the start time and the stop time, the CSS operation similar to the embodiment is repeated to
The presence or absence of disconnection of the element was examined.

The results are shown below. It should be noted that both the examples and the comparative examples were carried out on samples of 50 magnetic heads.

Number of Magnetic Heads Broken (Number) CSS Number (Times) Example 1 Comparative Example 5 1 10 0 5 20 20 6 6 30 1 8 40 3 12 50 3 12 Figure 4 is a graph created based on the above results Is. In FIG. 4, a is data of Example 1 and b is data of Comparative Example. From this result, when the number of times of CSS is 50, 24% of MR elements were disconnected in the comparative example, but 6% in Example 1. Therefore, according to the present invention, the occurrence rate of disconnection of the MR element is 24% to 6%. You can see that

[Second Embodiment] FIG. 5 shows a second embodiment of the magnetic memory device of the present invention. The second embodiment is a further improvement of the first embodiment.

As described above, in the magnetic memory device 1 of the first embodiment, the breakage of the MR element 11 can be reduced, but
It cannot be lost. This is because the magnetic head 10 is operated with a small flying height of 0.06 μm.
It is considered that this is because the MR element 11 comes into contact with the fine protrusions on the surface of the magnetic disk 20 during the floating operation, and an excessive current flows through the MR element 11 at that time. It is also possible that the levitation operation during seek is unstable, and that the MR element 11 contacts the surface of the magnetic disk 20 due to the shock applied in the levitation state.

As shown in FIG. 5, the second embodiment has a structure in which a means for detecting the contact between the magnetic head 10 and the magnetic disk 20 during the floating operation is added to the first embodiment. Also in the second embodiment, the magnetic head 10 performs the CSS operation on the magnetic disk 20. In FIG. 5, the first
The same components as those in the embodiment are designated by the same reference numerals.

In the magnetic storage device 1a of the second embodiment, the piezoelectric element 44 is brought into contact with a part of the slider 15 of the magnetic head 10, and the output signal of the piezoelectric element 44 is output to the piezoelectric output amplifier 4.
After being amplified at 5, the sense current control circuit 42 is fed back. When the magnetic head 10 comes into contact with the magnetic disk 20 during the levitation operation, the pressure applied to the piezo element 44 increases only at the moment when the magnetic head 10 comes into contact with the piezo element 4 accordingly.
The output voltage of 4 temporarily increases. The output voltage is amplified by the piezo output amplifier 45, and then the contact detection circuit 46.
Entered in. The contact detection circuit 46 detects the contact between the magnetic head 10 and the magnetic disk 20 based on the signal, and sends a control signal to the sense current control circuit 42 to temporarily stop the supply of the sense current.

The sense current control circuit 42 includes the MR element 11
When the control signal is received from the contact detection circuit 46 while the sense current is being supplied, the supply of the sense current is stopped only at that moment. Therefore, even if the MR element 11 comes into contact with the magnetic disk 20 during the levitation operation, there is no possibility that an excessive current will flow and the MR element 11 will be disconnected.

Regarding the magnetic memory device 1a of the second embodiment,
When the same confirmation test as in the first embodiment was performed, it was found to be 50
Even after performing the CSS operation once, the 50 MR elements 11 were not broken. Therefore, according to the second embodiment, it was found that the breakage of the MR element 11 during the reproducing operation can be prevented.

In the second embodiment, the piezo element 44, the piezo output amplifier 45 and the contact detection circuit 46 constitute contact detection means. However, another configuration may be used as long as it can detect the contact between the magnetic head 10 and the magnetic disk 20 during the floating operation. For example, an electrode may be provided on the slider 15 so that when the contact with the magnetic disk 20 occurs, a current flows at that moment.

In both of the above embodiments, the CSS operation is performed using the positive pressure type slider, but the negative pressure type slider may be used to always operate in the floating state. In that case, in the second embodiment, only the sense contact detecting means may be provided excluding the rotation speed detecting circuit 41.

[0049]

As described above, the magnetic head sense current control method and the magnetic memory device of the present invention have the effect that disconnection of the MR element due to the sense current is less likely to occur.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a magnetic storage device of the present invention.

FIG. 2 is a cross-sectional view of essential parts at a track center position of a magnetic head used in the magnetic storage device of FIG.

FIG. 3 is a cross-sectional view of essential parts of a magnetic disk used in the magnetic storage device of FIG.

FIG. 4 is a graph showing the relationship between the number of CSSs and the number of magnetic heads that have broken.

FIG. 5 is a block diagram showing the configuration of a second embodiment of the magnetic storage device of the present invention.

[Explanation of symbols]

 1, 1a Magnetic storage device 10 Magnetic head 11 MR element 12 Shunt film 13, 14 Shield film 15 Slider 16 Sliding surface 20 Magnetic disk 21 Substrate 22 Underlayer film 23 Recording layer 24 Protective film 30 Rotational drive device 31 Spindle 32 Motor 33 Fixed Tool 34 Conductive wire 40 Sense current control device 41 Rotation speed detection circuit 42 Sense current control circuit 43 Sense current supply circuit 44 Piezo element 45 Piezo output amplifier 46 Contact detection circuit

Claims (7)

[Claims] 1. When a magnetic head having a magnetoresistive effect element performs a CSS operation on a magnetic disk having a recording layer made of a metal film, at the time of start, the magnetic head floats above the surface of the magnetic disk. Sense current control for the magnetic head, wherein the sense current is supplied to the magnetoresistive effect element after that, and at the time of stop, the sense current supply is stopped before the magnetic head contacts the surface of the magnetic disk. Method. 2. When the magnetic head comes into contact with the surface of the magnetic disk while floating above the surface of the magnetic disk, the supply of the sense current is temporarily stopped at the time of contact. Magnetic head sense current control method. 3. When a magnetic head having a magnetoresistive effect element performs recording / reproducing of information in a state of being levitated from the surface of a magnetic disk having a recording layer made of a metal film,
When the magnetic head comes into contact with the surface of the magnetic disk, the supply of the sense current is temporarily stopped when the magnetic head comes into contact with the magnetic disk. 4. A magnetic storage device in which a magnetic head having a magnetoresistive effect element performs a CSS operation on a magnetic disk having a recording layer made of a metal film, wherein the magnetic head floats above the surface of the magnetic disk. A floating detection means for detecting whether or not there is a sense current, a sense current supply means for supplying a sense current to the magnetoresistive effect element, and a sense for the magnetoresistive effect element while the magnetic head is floating. A magnetic memory comprising: a current supply means; and a sense current control means for controlling the sense current supply means so as to stop the supply of the sense current while the magnetic head is not floating. apparatus. 5. A contact detection means for detecting contact of the magnetic head with the surface of the magnetic disk is provided,
5. The magnetic sensor according to claim 4, wherein the contact detection means controls the sense current control means so as to temporarily stop the supply of the sense current when the contact is detected while the magnetic head is flying. Storage device. 6. A magnetic storage device for recording / reproducing information while a magnetic head having a magnetoresistive effect element floats above the surface of a magnetic disk having a recording layer made of a metal film, wherein the magnetoresistive effect element is Sense current supply means for supplying sense current to the magnetic disk, contact detection means for detecting contact of the magnetic head with the surface of the magnetic disk, and supply of the sense current at the time of contact when the contact detection means detects contact. And a sense current control means for controlling the sense current supply means so as to temporarily stop the magnetic storage device. 7. The magnetic storage device according to claim 4, wherein the magnetoresistive effect element is exposed on a sliding surface of the magnetic head.