JPH0757203A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To perform the super high recording density reproduction properly without lowering the energizing life of a head even when the current density of a sense current is made large by causing the current opposite to the sense current to flow through an MR type magnetic head. CONSTITUTION:While the read/write operation of a magnetic recording/ reproducing device or the magnetic head 9 is stopped, an opposite current supply circuit 5 makes the current opposite to the sense current flowing through the MR type magnetic head 20 and with a prescribed current value or below than the sense current flow through the head 20. By such an operation, a thin film constitution atom in a magneto-resistance effect film is moved gradually to an original position again when the head 9 is driven. Thus, a micro void, etc., formed until then is filled by the atom moved again, and the disconnection in an element due to electro-migration is suppressed as a result.

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, and in particular, a recording / reproducing magnetic head in which a reproducing magnetoresistive effect type magnetic head and a recording electromagnetic induction type thin film magnetic head are laminated and combined. In a magnetic recording / reproducing apparatus equipped with
Even if the current density of the sense current flowing through the reproducing magnetoresistive magnetic head is increased, it is suitable for achieving ultra-high recording density reproduction without reducing the energization life of the magnetoresistive magnetic head. The present invention relates to a magnetic recording / reproducing device.

[0002]

2. Description of the Related Art A recording / reproducing magnetic head in which a reproducing magnetoresistive effect magnetic head and an electromagnetic induction type thin film magnetic head for recording are laminated and combined, and a thin film magnetic recording medium produced by sputtering or the like. As a magnetic recording / reproducing apparatus configured by combining, for example, an IE
Transactions on Magnetics MG 26, (1990) p. 1689-1693
(IEEE Trans. Mag., MAG-26,
(1990) p. 1689-1693, hereinafter referred to as the first document) is known. First above
According to the above document, the sense current density of the magnetoresistive film used for the magneto-sensitive film of the reproducing magnetoresistive magnetic head is 4.7 × 10 ⁷ A / cm ² (the various types described in the above documents). 1G by setting the value below the value calculated using numerical values
The recording capacity of BPI ² is achieved.

In addition, I E E TRANSACTION ON MAGNETICS M AG
27, (1991) P.I. 5280-5285 (IEEE
Trans. Mag. , MAG-27 (1991) P.I.
5280-5285, hereinafter referred to as the second document), the magnetic recording / reproducing apparatus has a sense current density of the magnetoresistive effect film of 3.3 × 10 ⁷ A / cm ² and a recording capacity of 2 G.
Achieved BPI ² .

However, the magnetic recording / reproducing apparatus described in the above-mentioned first and second documents is not specially devised so as to extend the energization life of the magnetoresistive effect magnetic head. Also,
The film thickness of the magnetoresistive film used for these is 15 n
m or more, the track interval between the electrodes provided on the magnetoresistive film is 2 μm or more, and the height of the track portion is 1 μm.
It is more than m.

[0005]

In the magnetic recording / reproducing apparatus described in the above-mentioned first and second documents, in order to further increase the magnetic recording density, the track width is made narrower or the linear recording density is further increased. There is a need to. However, along with this, the reproduction output of the magnetoresistive head for reproduction decreases, and the S / N ratio also decreases. Therefore, the output per unit track width of the magnetoresistive effect magnetic head must be increased as the track narrows and the linear recording density increases.

Several methods can be considered for increasing the output per unit track width, but the most effective method is to increase the sense current density flowing in the magnetoresistive film. However, in general, increasing the sense current density results in accelerating electromigration in the magnetoresistive film and reduces the energization life of the head. As is the case with the conventional magnetic recording / reproducing apparatus, when the sense current density is set to 3 × 10 ⁷ A / cm ² or more in order to realize high-density recording / reproducing, the electromagnetism increases due to increase in Joule heat. The migration is further accelerated, the energization life of the magnetoresistive magnetic head is significantly reduced, and there is a big problem that sufficient reliability cannot be obtained as a product.

The object of the present invention is to increase the current density of the sense current flowing through the reproducing magnetoresistive head.
An object of the present invention is to provide a magnetic recording / reproducing apparatus suitable for reproduction at an ultrahigh recording density without reducing the energization life of the magnetoresistive magnetic head.

[0008]

A magnetic recording / reproducing apparatus of the present invention comprises a recording / reproducing magnetic head in which a reproducing magnetoresistive magnetic head and a recording electromagnetic induction thin-film magnetic head are laminated and combined. In the magnetic recording / reproducing apparatus configured to include the magnetoresistive effect magnetic head, while the magnetic recording / reproducing apparatus is stopped, or when the read / write operation is not performed in the recording / reproducing magnetic head. It is characterized in that a reverse current supply means for supplying a current in a direction opposite to the sense current is provided.

Here, the reverse current supplied by the reverse current supply means is ½ of a predetermined sense current value.
To the specified sense current value.

Further, the magnetoresistive effect film used for the magneto-sensitive film of the magnetoresistive effect type magnetic head is (film thickness (nm) ×
The value of the height (μm) of the track portion between the electrodes provided on the magnetoresistive film × the track interval (μm)) is 60
It is characterized by being (nm · μm · μm) or less.

[0011]

The electromigration in the magnetoresistive film is accelerated as the sense current density flowing in the thin film is increased. Increasing the sense current density is
This leads to an increase in Joule heat generation, which further accelerates electromigration and exponentially decreases the energization life of the head. Electromigration is a phenomenon that occurs when electrons collide with atoms in a thin film, and as a result the atoms diffuse in one direction in which the electrons move, and after a large number of atoms move, voids are formed and the device Breaks. Normally, when a high current with a current density of 3 × 10 ⁷ A / cm ² or more is applied to the magnetoresistive effect element, the energization life of the magnetoresistive effect element is extremely short, 10 ⁶ hours or less. Therefore, in order to prevent disconnection of the element due to electromigration, it is sufficient to prevent the formation of voids even after the atoms have moved. For this purpose, it is effective to move the atoms again in the opposite direction.

According to the present invention, the magnetic recording / reproducing apparatus is provided with the reverse current supply means so that the magnetic recording / reproducing apparatus is stopped or the read / write operation is not performed in the recording / reproducing magnetic head. At
A current in the direction opposite to the sense current can be passed through the magnetoresistive magnetic head, whereby atoms in the magnetoresistive film can be gradually moved in the opposite direction.

Further, the value of the current in the opposite direction to the sense current is set in the range of 1/2 of the specified sense current to the value of the specified sense current. This is because when a too large reverse current is applied, the action of moving the thin film constituent atoms in the magnetoresistive effect film to the original position becomes too strong, and when it is too small, the effect of preventing electromigration is not provided.

Further, the magnetoresistive effect film used as the magnetosensitive film of the magnetoresistive effect type magnetic head has a film thickness (nm) and a height of a track portion between electrodes provided on the magnetoresistive effect film. The product of (μm) and track spacing (μm) is 60
It is characterized by being (nm · μm · μm) or less. As described above, the reason for defining the shape of the track portion of the magnetoresistive effect magnetic head is that if the volume of the magnetoresistive effect film becomes too large, Joule heat generation promotes electromigration. That is, controlling the Joule heat generation by defining the shape lowers the temperature of the track portion between the electrodes of the magnetoresistive effect film, and when the temperature lowers, atoms are less likely to diffuse, resulting in electromigration. Has the effect of suppressing. Joule heat is generally proportional to the applied power, but in reality it is
Since there is heat escape to the substrate and the like, the input power is not directly proportional to the temperature of the magnetoresistive film in the track portion.
Examining the relationship with the energization life due to electromigration, the energization life is found to be approximately proportional to the square root of the applied power.

By defining the shape of the track portion of the magnetoresistive effect magnetic head as in the present invention, the energization life is 10 even if the sense current density is 5 × 10 ⁷ A / cm ² or more.
^It has the effect of suppressing the value so that it does not fall below ⁹ hours. Therefore, the sense current density can be increased to 5 × 10 ⁷ A / cm ² or more by defining the film thickness, height, and spacing in this way, and the output of the magnetoresistive effect magnetic head is significantly increased. There is an action.

[0016]

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

FIG. 1 is a block diagram showing an embodiment of the magnetic recording / reproducing apparatus of the present invention, and FIG. 2 is a magnetoresistive effect type used as a reproducing portion of a magnetic head used in the magnetic recording / reproducing apparatus. FIG. 3 is a plan view showing the magnetic head portion.
FIG. 3 is a sectional view taken along line AA shown in FIG. 2.

As shown in FIG. 1, the magnetic recording / reproducing apparatus of this embodiment comprises a signal transmitting section 1 and a signal processing / signal detecting section 2.
, Signal recording circuit 3, sense current supply circuit 4, reverse current supply circuit 5, medium drive unit 6, head / medium interface unit 7, signal recording circuit 3, sense current supply circuit 4, and reverse current supply The magnetic head 9 includes a control unit 8 that controls the circuit 5, the medium driving unit 6 and the like. The present embodiment is characterized in that a reverse current supply circuit 5 is provided in addition to the configuration of a general magnetic recording / reproducing apparatus.

Here, the magnetic head 9 used in the head / medium interface section 7 of the magnetic recording / reproducing apparatus.
Uses an electromagnetic induction type thin film magnetic head for the recording section, and uses a magnetoresistive effect type magnetic head as shown in FIGS. 2 and 3 for the reproducing section.

In the magnetoresistive head, as shown in FIGS. 2 and 3, a lower shield film 12 made of a soft magnetic film is laminated and patterned on a substrate 11 made of ceramic or metal or semimetal having high thermal conductivity. Then, an insulating film 13 made of an Al ₂ O ₃ film or the like forming the gap portion is laminated thereon, and a magnetoresistive effect film 16 having a predetermined lateral bias magnetic field applying means 14 and vertical bias magnetic field applying means 15 is laminated thereon. Then
After patterning into a predetermined shape, the magnetoresistive film 1
The electrode 17 is formed on the electrode 6. After that, an insulating film 18 made of an Al ₂ O ₃ film or the like forming the upper gap portion is laminated, and then an upper shield layer 19 made of a soft magnetic film is laminated and patterned. As a result, the magnetoresistive head 20 is manufactured. In order to actually use it in the magnetic recording / reproducing apparatus, the electromagnetic induction type thin film head, which is the recording part, is laminated on this to form a composite magnetic head. Form.

The magnetoresistive effect magnetic head 20 manufactured as described above has a shape in which the film thickness of the magnetoresistive effect film 16 is 15 nm or less, the distance between the electrodes 17, that is, the track width is 2 μm or less, and the track portion The height is preferably 2 μm or less. As another method for defining the shape, (height of track portion (μm) × electrode gap (μm))
It is desirable to appropriately set the height of the track portion, the electrode interval, and the film thickness so that the value of (x film thickness (nm)) is 60 (μm · μm · nm) or less. As described above, the reason for defining the shape is that when the volume of the magnetoresistive effect film 6 becomes too large, heat generation promotes electromigration.

A NiFe film having a specific heat of about 0.45 (J / gH) and a film thickness of 20 nm is used as the magnetoresistive film, and has a track width of 4.5 μm and a track width of 3 mm.
In the case of μm, the sense current density in the magnetoresistive film is 1.5 × 10 ⁷ A / cm ² and the energization life is about 10 ¹¹ hours, but the current density is about 3 to 4 times this. When it was increased, the electrification life was reduced by several orders of magnitude. This is because the temperature of the magnetoresistive film in the track portion sharply rises due to abrupt Joule heat generation, and electromigration is accelerated. Therefore, the sense current density is
As a result of studying a shape that does not cause the temperature rise of the track portion (specifically, the temperature rise must be about 10 ° C. or less) even if the heat conductivity is 3 to 4 times, the thermal conductivity is 3 W / mK or more. It was found that it is sufficient to use a substrate and set the thickness of the NiFe film to 15 nm or less, the track width to 2 μm or less, and the height of the track portion to 2 μm or less. Even if the above conditions are not all satisfied, the NiFe film thickness (nm), track width (μm), and track portion height (μ)
It was confirmed that the same effect can be obtained when the value multiplied by m) is 60 (nm · μm · μm) or less.

As the magnetoresistive film, NiC is used.
When an o film, a NiFeCo film, or an artificial lattice film (also called a superlattice) in which transition metals are multilayered is used, the specific heat of these films is almost the same as that of the NiFe film. It became clear that the same effect was obtained by.

The magnetic recording / reproducing apparatus of the present embodiment constructed as described above operates as follows. That is, the specially provided reverse current supply circuit 5 is controlled by the control unit 8, and while the read / write operation of the magnetic recording / reproducing apparatus or the magnetic head 9 is stopped, the reverse current supply circuit 5 has the magnetoresistive effect. A current having a direction opposite to the sense current flowing in the magnetic head 20 and having a value equal to or less than a specified sense current value is flown in the magnetoresistive magnetic head 20.

As described above, it is possible to intermittently flow the current in the direction opposite to the sense current direction from the reverse current supply circuit 5 while the operation of the magnetic head 9 is stopped. Has a function of gradually moving the atoms constituting the thin film in the magnetoresistive effect film diffused due to electromigration to the original position again during the driving. By this action, the previously formed microvoids and the like are filled with the atoms that have moved again, and as a result, the disconnection of the element due to electromigration can be suppressed. Here, it is desirable that the current flowing in the direction opposite to the sense current flowing through the magnetoresistive effect magnetic head 20 is equal to or less than the specified sense current value and is equal to or more than 1/2 of the specified sense current. The reason is that when a too large reverse current is applied, the action of moving the thin film constituent atoms in the magnetoresistive effect film to the original position becomes too strong, and when it is too small, the effect does not appear.

The reverse current supply circuit 5 and the control unit 8 are arranged so that a current in the direction opposite to the sense current flows through the magnetoresistive head when the magnetic recording / reproducing apparatus itself is out of operation at night. May be configured.

FIG. 4 shows how the energization life time of the magnetoresistive head 20 changes with the product of the magnitude of the reverse current and its energization time, using the current density of the magnetoresistive film as a parameter. It is the result. As described above, flowing the current in the opposite direction to the sense current from the reverse current supply circuit 5 has an effect of significantly increasing the energization life of the magnetoresistive head 20. Assuming that the energization life time that can withstand practical use is about 10 ⁹ hours, the sense current flowing in the magnetoresistive film is 5 × 10 ⁷ A in terms of current density.
It was confirmed that a value of / cm ² or more was possible. Therefore, in the magnetic recording / reproducing apparatus according to the present embodiment, the output of the magnetic head 9 and the S / N ratio can be greatly increased.

FIG. 5 shows the relationship between the square root value of (the height of the track portion of the magnetoresistive effect film × the electrode interval × the film thickness ÷ 15) and the energization life time of the magnetoresistive effect type magnetic head 20. It is a figure which shows the result investigated by using density as a parameter. The smaller the square root value is, the longer the energization life time is. When the sense current density is 5 × 10 ⁷ A / cm ² , the energization life time is 2 or less and the energization life time is a practical life time. More than 10 ⁹ hours. Here, the meaning of (height of track portion of magnetoresistive film × electrode interval × film thickness ÷ 15) means that the volume of the track portion of magnetoresistive film is 15 (nm) which is the maximum value of film thickness. It means to normalize.

As in this embodiment, the film thickness of the magnetoresistive film in the magnetoresistive head 20 is 15 nm or less, the height of the track portion between the electrodes is 2 μm or less, and the electrode interval is 2 μm or less. Furthermore (track height x
It is necessary to set the height of the track portion, the electrode interval, and the film thickness values so that the value of the square root of (electrode interval × film thickness ÷ 15) is 2 or less. The sense current density is 5 × 10 ⁷ A / cm ²
Even if the above is the case, the amount of heat generated in the track portion of the magnetoresistive film is controlled so that the energization life is not shorter than 10 ⁹ hours.

The square root of (the height of the track portion of the magnetoresistive effect film × the electrode interval × the film thickness ÷ 15) is 2 or less means that (the height of the track portion of the magnetoresistive effect film × the electrode). It is equivalent to (distance x film thickness) being 60 (μm · μm · nm) or less.

Therefore, the magnetic recording / reproducing apparatus having the reverse current supply circuit 5 according to the present embodiment, and the magnetoresistive effect in which the height of the track portion of the magnetoresistive film, the electrode interval, and the film thickness of the magnetoresistive film are controlled respectively. When combined with a magnetic head of the magnetoresistive type, the sense current density can be sufficiently increased to 5 × 10 ⁷ A / cm ² or more, and the output and S / N ratio of the magnetoresistive magnetic head 20 can be significantly increased. There is an increasing effect.

As is apparent from the above description, according to the above embodiment, the magnetic recording / reproducing apparatus or the magnetic head serving as the reproducing unit of the magnetic head is utilized while the magnetic recording / reproducing apparatus or the magnetic head is stopped. The thin film constituent atoms in the magnetoresistive film diffused due to electromigration at the time of driving the magnetic head are gradually turned to the reverse direction again by passing a current in the direction opposite to the sense current direction only in the resistance effect type head part. It has the effect of moving it to its original position. By this action, the microvoids and the like that have been formed up to that point are filled again, and as a result, it is possible to suppress the disconnection of the element due to electromigration.
This has the effect of significantly increasing the energization life time of the magnetoresistive head. Therefore, the sense current flowing in the magnetoresistive head is also converted into the current density of the magnetoresistive film at 5 × 10 ⁷ A / It can be significantly increased to cm ² or more.

Therefore, in the magnetic recording / reproducing apparatus according to the present embodiment, the output of the magnetic head and the S /
The N ratio can be greatly increased, and the surface density is 3G.
A high magnetic recording density of BPI ² or higher can be achieved.

In the magnetoresistive head used in the magnetic recording / reproducing apparatus of this embodiment, the magnetoresistive film has a film thickness of less than 15 nm, and the height of the track portion between the electrodes provided on the magnetoresistive film is high. The distance between the electrodes is less than 2 μm, or the height of the track portion is set so that the value of (height of the track portion × electrode distance × film thickness) is 60 (μm · μm · nm) or less. Setting the values of the electrode interval and the film thickness appropriately makes the sense current density 5 × 10 ⁷ A / c.
Even if m ² or more, the energization life of the magnetoresistive head is 1
It has an effect of suppressing the heat generation amount of the track portion so as not to fall below ⁰⁹ hours. Therefore, the sense current density is 5 × 10 ⁷ A / cm ² by controlling the film thickness of the magnetoresistive film, the height of the track portion, and the track interval as described above.
It is possible to greatly increase the above, and there is an effect of greatly increasing the output of the magnetic head and the S / N ratio, and it is possible to increase the recording density in the magnetic recording / reproducing apparatus.

[0035]

As is apparent from the above description, according to the present invention, even if the current density of the sense current flowing through the reproducing magnetoresistive head is increased, the magnetoresistive head is energized. It is possible to provide a magnetic recording / reproducing apparatus suitable for reproduction at an extremely high recording density without shortening the life.

[Brief description of drawings]

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

FIG. 2 is a plan view showing a magnetoresistive effect magnetic head used in the magnetic recording / reproducing apparatus shown in FIG.

3 is a cross-sectional view taken along the line AA of the plan view shown in FIG.

FIG. 4 shows how the energization life time of the magnetoresistive effect magnetic head 20 changes with the product of the magnitude of the reverse current flowing through the magnetoresistive effect magnetic head and its energization time, and the current density of the magnetoresistive effect film. The figure which shows the result investigated by using as a parameter.

FIG. 5 shows the relationship between the square root value of (the height of the track portion of the magnetoresistive effect film × the electrode interval × the film thickness ÷ 15) and the energization life time of the magnetoresistive effect type magnetic head with the sense current density as a parameter. The figure which shows the examined result.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Signal transmission part, 2 ... Signal processing / signal detection part, 3 ... Signal recording circuit, 4 ... Sense current supply circuit, 5 ... Reverse current supply circuit, 6 ... Medium drive part, 7 ... Head / medium interface part, 8 ... Control units 8, 9 ... Magnetic heads 9, 11 ... Substrate,
12 ... Lower shield film, 13 ... Insulating film, 14 ... Transverse bias magnetic field applying means, 15 ... Vertical bias magnetic field applying means, 16
... Magnetoresistive film, 17 ... Electrode, 18 ... Insulating film, 19
... upper shield layer, 20 ... magnetoresistive effect magnetic head.

Claims (3)

[Claims] 1. A magnetic recording / reproducing apparatus comprising a recording / reproducing magnetic head in which a reproducing magnetoresistive magnetic head and a recording electromagnetic induction thin-film magnetic head are laminated and combined. Reverse current supply means for supplying a current in the direction opposite to the sense current to the magnetoresistive effect magnetic head during the operation stop of the magnetic recording / reproducing apparatus or at the timing when the read / write operation is not performed in the recording / reproducing magnetic head. A magnetic recording / reproducing apparatus provided with. 2. The reverse current supplied by the reverse current supply means is set between 1/2 of a predetermined sense current value and a predetermined sense current value. The magnetic recording / reproducing apparatus described. 3. A magnetoresistive film used as a magneto-sensitive film of the magnetoresistive magnetic head is (film thickness (nm) × highness of a track portion between electrodes provided on the magnetoresistive film). Value (length (μm) × track spacing (μm)) is 60 (nm
.Mu.m.mu.m) or less. 2. The magnetic recording / reproducing apparatus according to claim 1, wherein