JPH06301935A - Thin film magnetic head of magnetoresistance effect type - Google Patents

Abstract

PURPOSE:To drive a magnetic head while a sense current and a bias current are individually set at the optimum value even making the number of terminals of a reproducing circuit minimum. CONSTITUTION:This is an MR head having a reproducing circuit which consists of a sense circuit 32 and a bias circuit 31. An MR element is a resistance RMR and a sense current IMR is supplied in the sense circuit 32. On the other hand, a bias conductor of the bias circuit 31 is a resistance RBias and a bias current IBias is supplied to the bias circuit 31. The reproducing circuit has the sense circuit 32 and the bias circuit 31 connected in parallel, with a variable resistance R consisting of a resistor connected in series to the bias circuit 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a magnetoresistive effect element whose resistivity changes according to a signal magnetic field from a magnetic recording medium, and detects a resistance change of the magnetoresistive effect element as a reproduction output voltage. Type thin film magnetic head.

[0002]

2. Description of the Related Art In recent years, as hard disk devices have become smaller and have larger capacities, particularly in applications where portable computers such as notebook computers are considered, for example, a 2.5-inch hard disk. The demand for equipment is increasing.

In such a small hard disk, the medium speed becomes slow depending on the disk diameter. Therefore, in the conventional induction type magnetic head in which the reproducing output depends on the medium speed, the reproducing output is lowered and the increase in capacity is hindered. Has become.

However, a magnetoresistive effect type magnetic head which detects a change in resistance of a magnetoresistive effect element (hereinafter, simply referred to as an MR element) whose resistivity changes according to a magnetic field as a reproduction output voltage has a reproduction output at a medium speed. Since it has the feature that it can obtain a high reproduction output even at a low medium speed,
It is attracting attention as a magnetic head that realizes a large capacity in a small hard disk.

Conventionally, in order to realize the above-mentioned MR head as a magnetic head of a hard disk drive, a magnetoresistive effect type thin film magnetic having a structure in which a thin film MR element is sandwiched between a slider material and a lower shield core and an upper shield core. A head (hereinafter referred to as an MR head) is formed.

In this MR head, as a reproducing circuit, a sense circuit for supplying a sense current to the MR element and a bias circuit for applying a bias magnetic field to the MR element by supplying a bias current are provided. .

Generally, the change of the resistance value with respect to the magnetic field component in the hard axis direction of the MR element is as shown in the RH characteristic curve of FIG. 11, as the absolute value of the magnetic field component H in the hard axis direction increases. It has a characteristic that the value R gradually decreases.

When reproducing a recording signal of a magnetic recording medium with this MR head, a predetermined bias current is applied to the bias circuit and a fixed bias magnetic field H _B is applied in advance in the hard axis direction of the MR element. , Its operating point A is R-
It is arranged so that it comes to the center of the straight line portion of the H characteristic curve. This is to increase the detection sensitivity.

When a signal magnetic field from the magnetic recording medium is input in such a state, the resistance value of the MR element changes due to the magnetic field component of the signal magnetic field in the hard axis direction.
Since a constant sense current flows in the MR element through the sense circuit, the voltage V across the MR element changes according to the change in its resistance value. Therefore, the information magnetically recorded on the magnetic recording medium can be known by detecting the voltage across the MR element.

In the conventional MR head, the reproducing circuit is constructed by connecting the sense circuit and the bias circuit separately or in series (for example, Japanese Patent Laid-Open No. Sho 60-60).
47222).

[0011]

However, when the sense circuit and the bias circuit are separate circuits, it is necessary to take out terminals from each circuit, and therefore four terminals are required for the reproducing circuit. Therefore, there is a problem that the wiring work in the MR head assembling process becomes complicated, and it is necessary to widen the area for forming the terminal pattern, and the head itself becomes large.

On the other hand, when the reproducing circuit is constructed by connecting the sense circuit and the bias circuit in series, the reproducing circuit has two terminals.
All that is needed is a book, and the problems described above do not occur. But,
The following new problems arise.

That is, the sense current supplied to the sense circuit and the bias current supplied to the bias circuit have different optimum current values depending on the RH characteristics of the MR element and the specifications of the MR head. However, in the MR head, since the sense circuit and the bias circuit are connected in series, each current cannot be controlled individually. Therefore, even if the current value of one circuit is set to the optimum current value, the current value of the other circuit deviates from the optimum current value, and the reproduction output characteristic deteriorates.

The present invention has been made in view of the above problems, and an object of the present invention is to individually control the sense current and the bias current while minimizing the number of terminals of the reproducing circuit. An object of the present invention is to provide a magnetoresistive thin-film magnetic head that can be operated by setting the sense current and the bias current to optimum current values.

[0015]

According to the present invention, a sense circuit 32 for supplying a sense current I _MR to a magnetoresistive effect element 1 having a magnetoresistive effect, and a bias current I _Bias are supplied to the magnetoresistive effect element. In the magnetoresistive thin-film magnetic head having a reproducing circuit composed of a bias circuit 31 for applying a bias magnetic field to the magnetic field sensor 1, the current values I _MR and I _MR of the sense circuit 32 and the bias circuit 31, respectively.
A resistor 23 for adjusting _Bias is provided and configured.

In this case, the sense circuit 32 and the bias circuit 31 are connected in parallel, and the resistor 23 is connected to the bias circuit 31.
May be connected to form a reproducing circuit, or the reproducing circuit may be formed by connecting the sense circuit 32 and the bias circuit 31 in series and connecting the resistor 23 in parallel to one or both circuits. You may do it.

The resistor 23 can be formed by chemical or physical or a combination thereof, and chemical or physical etching.

[0018]

In the magnetoresistive thin film magnetic head (hereinafter simply referred to as MR head) according to the present invention, the sense current I _MR is passed through the sense circuit 32 to the magnetoresistive effect element (hereinafter simply referred to as MR element) 1. Flow, bias circuit 31
A bias magnetic field is applied to the MR element 1 by supplying the bias current I _Bias to the MR element 1.

In such a state, a magnetic recording medium
When the signal magnetic field from
The resistance value R of the MR element 1 depends on the direction magnetic field component._MRChanges
To do. As described above, the MR element 1 includes the sense circuit 32.
Through a constant sense current I _MRIs flowing, so MR
The voltage V across element 1 is its resistance value R_MRChanges according to changes in
Will be changed. Therefore, the voltage across the MR element 1
By detecting V, magnetic recording is performed on the magnetic recording medium.
You can find out what information you have.

The sense current I _MR supplied to the sense circuit 32 and the bias current I _Bias supplied to the bias circuit 31 _depend on the RH characteristics of the MR element 1 and the specifications of the MR head. The optimum current values of _MR and I _Bias are different.

In the MR head according to the present invention,
Current value I of the bias circuit 32 and the bias circuit 31_MRAnd I
_BiasSince the resistor 23 for adjusting
Each current of the sense circuit 32 and the bias circuit 31 in the body 23
Value I_MRAnd I_BiasBy adjusting the sense circuit 3
2 and the current value I supplied to the bias circuit 31_MRAnd I
_BiasCan be set individually to the optimum current value.
It

Specifically, the resistor 2 formed by chemical or physical or a combination thereof is trimmed by chemical or physical etching to form the resistor 2.
By adjusting the electric resistance value R of No. 3, the current values I _MR and I _Bias supplied to the sense circuit 32 and the bias circuit 31 can be individually set to the optimum current values.

Further, in the present invention, the sense circuit 32
And the bias circuit 31 are connected in parallel, or the sense circuit 32 and the bias circuit 31 are connected in series,
Only two terminals are required for the reproducing circuit.

As described above, in the MR element according to the present invention, the number of terminals of the reproducing circuit can be set to the minimum number, and the sense current I _MR and the bias current I _Bias can be controlled individually. The sense current I _MR and the bias current I _Bias can be set to the optimum current values and operated.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Several embodiments in which the magnetoresistive effect thin film magnetic head according to the present invention is applied to a vertical magnetoresistive effect thin film magnetic head will be described below with reference to FIGS.

First, as shown in FIG. 1B, the MR head according to the first embodiment has a magnetoresistive effect element (hereinafter, simply referred to as MR).
An element) 1 is sandwiched between a lower shield magnetic body 2 and an upper shield magnetic body 3.

Specifically, on a non-magnetic substrate 11 having an insulating layer (not shown) made of alumina or the like formed on its surface in advance,
A lower shield magnetic body 2 made of a magnetic film such as Ni-Fe is formed, and an insulating layer 12 made of alumina or the like forming a first reproduction gap g1 is laminated on the lower shield magnetic body 2. Then, on this insulating layer 12, an MR element 1 made of two layers of ferromagnetic thin films having a magnetoresistive effect, for example, a Fe—Ni film, is formed with a non-magnetic layer sandwiched therebetween, and further on this MR element 1. A lower insulating layer 13 made of SiO ₂ or the like is formed.

Then, on the lower insulating layer 13, the M
A bias conductor 14 for applying a bias magnetic field to the R element 1 and a rear end electrode 15 for supplying a sense current to the MR element 1 are formed in the same wiring layer, and the bias conductor 14 and the rear end electrode 15 are formed. The upper insulating layer 16 made of SiO ₂ or the like is formed on the upper surface including
An upper shield magnetic body 3 made of a magnetic film such as Fe-Ni
Are stacked to form the MR head according to the first embodiment.

Particularly, in the first embodiment, the lower insulating layer 13 and the upper insulating layer 16 are removed from the surface (sliding surface) a facing the magnetic recording medium a little in the depth direction. The second reproduction gap g is added to the removed portion.
A nonmagnetic metal film 17 forming 2 is formed. The non-magnetic metal film 17 is formed in contact with the tip of the MR element 1 on the sliding surface side in the lower part thereof, and in contact with the upper shield magnetic body 3 in the upper part thereof.

The MR element 1 is arranged so that its longitudinal direction is perpendicular to the sliding surface a, and one end surface of the MR element 1 is set to the sliding surface a.
It has been exposed to. Normally, a front end electrode and a rear end electrode are formed at a sliding surface side end (hereinafter referred to as a front end) of the MR element 1 and at a position separated from the front end by a predetermined distance. In the example, the nonmagnetic metal film 17 forming the second reproduction gap g2 also serves as the tip electrode.

With this structure, the MR element 1 has a sense current I _MR along the longitudinal direction of the MR element 1 (that is, in the direction orthogonal to the sliding surface a), as shown in FIG. 1A.
Therefore, in this MR head, the sense current I _MR flows in the same direction as the direction of the signal magnetic field from the magnetic recording medium. Therefore, in the MR element 1, the rear end and the rear end electrode 18 of the non-magnetic metal film 17 which constitutes the front end electrode.
The region between the front ends of the MR elements exhibits a magnetoresistive effect, and this region constitutes the magnetically sensitive portion of the MR element 1.

As shown in FIG. 1A, the bias conductor 14 is connected to the rear end portion of the upper shield magnetic body 3 and passes the sense current I _MR through the upper shield magnetic body 3 and the nonmagnetic metal film 17 to the MR element 1. Is formed by branching from the input side wiring pattern 21 which is supplied to the input side wiring pattern 21 and the terminal end thereof is connected to the wiring pattern 22 of the rear end electrode 15 for returning the sense current I _MR from the MR element 1. Further, the input side wiring pattern 21 has an input terminal φin (see FIG. 2).
And the output terminal φout (see FIG. 2) is connected to the routing pattern 22 of the rear end electrode 15.

Further, in the first embodiment, the resistor 23 is connected to the bias conductor 14. Actually, a part of the bias conductor 14, in the illustrated example, a part of the path of the bias conductor 14 from the MR element 1 to the terminal end is removed, and the resistor 23 is formed in the removed part, and The bias conductor 14 is electrically connected through the resistor 23.

As an example of forming the resistor 23, for example, as shown in FIG. 3A, the bias conductor 14 and the rear end electrode 1 are formed.
In the formation of the wiring pattern 24 including 5, especially in the patterning by the photolithography and the etching process, a part of the wiring pattern 24 is disconnected and patterned, and then a resistor made of a material having an etching rate different from that of the wiring pattern 24. 23 is deposited by, for example, a sputtering method, a plating method, a vapor deposition method, or the like. As the material of the resistor 23, for example, a metal layer such as Al or Cu, a high melting point metal layer such as Ti or W, a high melting point metal silicide layer, or a polycrystalline silicon layer can be used.

After that, as shown in FIG. 3B, a part of the resistor 23, for example, both ends in the width direction and an upper portion in the thickness direction are removed by etching to form a resistor 23 having a desired resistance value. Here, the resistance value of the resistor 23 is as follows, where m is the length of the resistor 23, w is the width of the resistor 23, t is the thickness of the resistor 23, and ρ is the resistivity of the resistor material. It is determined by the number 1.

[0036]

[Equation 1]

As an etching method for forming the resistor 23, for example, wet etching, ion milling, RIE (reactive ion etching), laser cutting or the like can be adopted.

In consideration of the step coverage of the laminated film formed on the wiring pattern 24, the resistor 23 is formed by being embedded in the removed portion of the wiring pattern 24 as shown in FIG. May be.

FIG. 2 shows an equivalent circuit of the reproducing circuit from the input terminal φin connected to the input side wiring pattern 21 to the output terminal φout connected to the routing pattern 22 of the rear end electrode 15. As can be seen from this equivalent circuit, in the reproducing circuit, the bias conductor 14 is the resistor R _Bias , the bias circuit 31 is supplied with the bias current I _Bias , the MR element 1 is the resistor R _MR , and the sense current I _Bias.
A sense circuit 32 to which _MR is supplied is connected in parallel, and a variable resistor R constituted by a resistor 23 is connected in series to the bias circuit 31 to form a circuit.

The ratio between the bias current value I _Bias and the sense current value I _MR is given by the following equation 2.

[0041]

[Equation 2]

From the above equation 2, the bias current value I _Bias
And the sense current value I _MR is the resistance value R of the resistor 23.
It can be seen that it is determined by

As described above, in the MR head according to the first embodiment, the sense current I _MR flows to the MR element 1 through the sense circuit 32, and the bias current I _Bias is supplied to the bias circuit 31 to cause the MR element 1 to _operate. A bias magnetic field is applied to.

In such a state, a magnetic recording medium
When the signal magnetic field from
The resistance value R of the MR element 1 depends on the direction magnetic field component._MRChanges
To do. As described above, the MR element 1 includes the sense circuit 32.
Through a constant sense current I _MRIs flowing, so MR
The voltage V across element 1 is its resistance value R_MRChanges according to changes in
Will be changed. Therefore, the voltage across the MR element 1
By detecting V, magnetic recording is performed on the magnetic recording medium.
You can find out what information you have.

Normally, the sense current I _MR supplied to the sense circuit 32 and the bias current I _Bias supplied to the bias circuit 31 are different depending on the RH characteristics of the MR element 1 and the specifications of the MR head. The optimum current values of _MR and I _Bias are different.

In the MR head according to the first embodiment, the sense circuit 32 and the bias circuit 31 are connected in parallel,
Moreover, since the resistor 23 is connected in series to the bias circuit 31 to configure the reproducing circuit, the resistor 2
3, each current value I of the sense circuit 32 and the bias circuit 31
By adjusting the _MR and I _Bias, the current value I _MR and I _Bias is supplied to the sense circuit 32 and bias circuit 31
Can be individually set to the optimum current value.

Specifically, as shown in FIG. 3, the resistor 23 formed by the sputtering method, the plating method, the vapor deposition method or the like is
The resistor 23 is trimmed by wet etching, ion milling, RIE, laser cutting, or the like.
It is possible to adjust the electric resistance value R of the above and set the current values I _MR and I _Bias supplied to the sense circuit 32 and the bias circuit 31 individually to the optimum current values.

Moreover, in the first embodiment, since the sense circuit 32 and the bias circuit 31 are connected in parallel, two terminals (one input terminal φi) are provided as terminals of the reproducing circuit.
n and one output terminal φout), the wiring work in the MR head assembling process can be simplified, the area for forming the terminal pattern can be narrowed, and the MR head itself can be miniaturized. .

Next, the MR head according to the second embodiment is shown in FIG.
And FIG. 6 will be described. The same reference numerals are given to those corresponding to those in FIGS. 1 and 2.

The MR head according to the second embodiment is shown in FIG.
As shown in FIG. 5, the MR head has substantially the same structure as that of the MR head according to the first embodiment, but the end of the rear end electrode 15 extends from the branch point of the input side wiring pattern 21 in the bias conductor 14 to the MR head.
The point where the resistor 23 is connected to the path up to the element 1 and the resistor 23 in the bias conductor 14 is the input side wiring pattern 21.
It is different in that it is connected to the path from the branch point to the connection point with the terminal end of the rear end electrode 15.

The equivalent circuit of the reproducing circuit of the MR head according to the second embodiment is, as shown in FIG. 6, a bias circuit 31 having a resistance R _Bias and a sense circuit 3 having a resistance R _MR.
2 is connected in series, and the variable resistance R formed by the resistor 23 is connected in parallel to the sense circuit 32.

The ratio between the bias current value I _Bias and the sense current value I _MR is given by the following _expression 3.

[0053]

[Equation 3]

From the above equation 3, the bias current value I _Bias
It can be seen that the ratio of the sense current value I _MR to the sense current value I _MR is determined by the resistance value R of the resistor 23 as in the first embodiment.

As described above, also in the MR head according to the second embodiment, as in the MR head according to the first embodiment, the number of terminals of the reproducing circuit can be set to the minimum number and the sense current can be set. I _MR and the bias current I _Bias can be controlled individually, and the MR head can be operated by setting the sense current I _MR and the bias current I _Bias to optimum current values.

Next, the MR head according to the third embodiment is shown in FIG.
And it demonstrates based on FIG. The same reference numerals are given to those corresponding to those in FIGS. 1 and 2.

The MR head according to the third embodiment is shown in FIG.
As shown in FIG. 5, the MR head according to the first embodiment has substantially the same structure, but the routing pattern 22 of the rear end electrode 15 also serves as the bias conductor 14, and the routing pattern 22 (bias conductor The difference is that the rear end electrode 15 from the MR element 1 is connected via a resistor 23 in the path to the output terminal φout in 14).

The equivalent circuit of the reproducing circuit of the MR head according to the third embodiment is, as shown in FIG. 8, a bias circuit 31 having a resistance R _Bias and a sense circuit 3 having a resistance R _MR.
2 is connected in series, and further, the bias circuit 31 is connected in parallel with the variable resistor R constituted by the resistor 23.

The ratio between the bias current value I _Bias and the sense current value I _MR is given by the following _expression 4.

[0060]

[Equation 4]

From the above equation 4, the bias current value I _Bias
It can be seen that the ratio of the sense current value I _MR to the sense current value I _MR is determined by the resistance value R of the resistor 23 as in the first embodiment.

As described above, also in the MR head according to the third embodiment, as in the MR head according to the first embodiment, the number of terminals of the reproducing circuit can be set to the minimum number and the sense current can be set. I _MR and the bias current I _Bias can be controlled individually, and the MR head can be operated by setting the sense current I _MR and the bias current I _Bias to optimum current values.

Next, the MR head according to the fourth embodiment is shown in FIG.
And it demonstrates based on FIG. The same reference numerals are given to those corresponding to those in FIGS. 1 and 2.

The MR head according to the fourth embodiment is shown in FIG.
As shown in FIG. 11, the MR head according to the first embodiment has almost the same configuration, but the first resistor 23a is inserted in the midway path of the bias conductor 14 branched and routed from the input side wiring pattern 21. The connected point and the rear electrode 15
Is branched into two, one branch pattern 15a is connected to the path from the branch point of the input side wiring pattern 21 to the MR element 1 in the bias conductor 14, and the other branch pattern 15b is the bias conductor. MR element 1 out of 14
It is different in that it is connected via a second resistor 23b to a path from the top to the output terminal φout (see FIG. 10) side.

In the equivalent circuit of the reproducing circuit of the MR head according to the fourth embodiment, as shown in FIG. 10, a bias circuit 31 having a resistance R _Bias and a sense circuit 32 having a resistance R _MR are connected in series. Further, in the sense circuit 32, a first variable resistor R composed of a first resistor 23a is provided.
₁ is connected in parallel, and the bias circuit 31 is connected in parallel with the second variable resistor R ₂ formed by the second resistor 23b.

The ratio between the bias current value I _Bias and the sense current value I _MR is given by the following equation 5.

[0067]

[Equation 5]

From the above equation 5, the bias current value I _Bias
It is understood that the ratio of the sense current value I _MR and the sense current value I _MR is determined by the resistance values R ₁ and R ₂ of the first resistor 23a and the second resistor 23b.

As described above, also in the MR head according to the fourth embodiment, as in the MR head according to the first embodiment, the number of terminals of the reproducing circuit can be set to the minimum number and the sense current can be set. I _MR and the bias current I _Bias can be controlled individually, and the MR head can be operated by setting the sense current I _MR and the bias current I _Bias to optimum current values.

[0070]

As described above, according to the magnetoresistive thin-film magnetic head of the present invention, the sense circuit for supplying the sense current and the bias current are supplied to the magnetoresistive effect element having the magnetoresistive effect. In a magnetoresistive thin-film magnetic head having a reproducing circuit composed of a bias circuit for applying a bias magnetic field to the magnetoresistive element, a resistor for adjusting each current value of the sense circuit and the bias circuit is provided. With this configuration, the sense current and the bias current can be individually controlled while the number of terminals of the reproducing circuit is minimized, and the sense current and the bias current can be set to the optimum current values and operated.

[Brief description of drawings]

FIG. 1 is a two-sided view showing a configuration of a main part of an MR head according to a first embodiment, where FIG. 1A is a plan view thereof and FIG.
3 is a cross-sectional view taken along line AA in FIG.

FIG. 2 is an equivalent circuit diagram of a reproducing circuit of the MR head according to the first embodiment.

3A to 3C are manufacturing process diagrams showing a method of forming a resistor and adjusting a resistance value thereof. FIG. 3A shows a state in which the resistor is formed, and FIG. 3B shows a resistance value obtained by trimming the resistor. Shows the adjusted state.

FIG. 4 is a cross-sectional view showing another method of forming a resistor.

FIG. 5 is a plan view showing a configuration of a main part of an MR head according to a second embodiment.

FIG. 6 is an equivalent circuit diagram of a reproducing circuit of the MR head according to the second embodiment.

FIG. 7 is a plan view showing a configuration of a main part of an MR head according to a third embodiment.

FIG. 8 is an equivalent circuit diagram of a reproducing circuit of the MR head according to the third embodiment.

FIG. 9 is a plan view showing a configuration of a main part of an MR head according to a fourth example.

FIG. 10 is an equivalent circuit diagram of a reproducing circuit of an MR head according to a fourth example.

FIG. 11 is a characteristic diagram showing RH characteristics of the MR element.

[Explanation of symbols]

 1 MR element 2 Lower shield magnetic body 3 Upper shield magnetic body 11 Non-magnetic substrate 12 Insulating layer 13 Lower insulating layer 14 Bias conductor 15 Rear end electrode 16 Upper insulating layer 17 Non-magnetic metal layer (tip electrode) 21 Input side wiring pattern 22 Routing patterns 23, 23a, 23b Resistors

Claims (4)

[Claims] 1. A sense circuit for supplying a sense current to a magnetoresistive effect element having a magnetoresistive effect, and a bias circuit for applying a bias magnetic field to the magnetoresistive effect element by supplying a bias current. A magnetoresistive thin-film magnetic head having a reproducing circuit, comprising a resistor for adjusting each current value of the sense circuit and the bias circuit. 2. The magnetoresistive thin-film magnetic head according to claim 1, wherein the sense circuit and the bias circuit are connected in parallel, and the resistor is connected to the bias circuit. 3. The magnetoresistive thin film magnetic head according to claim 1, wherein the sense circuit and the bias circuit are connected in series, and one or both circuits are connected in parallel with the resistor. . 4. The resistor is formed by a chemical film forming means, a physical film forming means or a combination thereof, and is formed by chemical or physical etching. Alternatively, the magnetoresistive thin-film magnetic head described in 3 above.