JP3148703B2 - Magnetoresistive head and magnetic recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing magnetic head having high sensitivity and a magnetic recording / reproducing apparatus using the magnetic head.

[0002]

2. Description of the Related Art With the increase in the density of magnetic recording, Juliere's Phys.
The application of a multilayer film exhibiting a magnetic tunneling phenomenon described in “Tunneling between Ferromagnetic Films”, published in ics Letters, Vol. 54A (1975), Issue 3, page 225, to a magnetoresistive head is being studied. This magneto-resistance effect type head has a magneto-resistance effect element having a structure in which an insulating layer is sandwiched between two magnetic layers, and when the magnetization directions of the two magnetic layers of the magneto-resistance effect element are parallel. The recording magnetization is detected by utilizing the fact that electrons are more likely to tunnel through the insulating layer than when they are antiparallel. Change the coercive force with two magnetic layers,
With a structure in which the antiferromagnetic layer is in contact with one of the magnetic layers, only the magnetization of one of the magnetic layers is reversed by the action of the leakage magnetic field from the recording magnetization, and the magnetization directions of the two magnetic layers become parallel. The recording magnetization is detected by detecting the magnitude of a tunnel current flowing through the insulating layer.

In a multilayer film exhibiting such a magnetic tunneling phenomenon, it is most important to form a flat insulating layer having excellent characteristics. As a method of forming a relatively excellent insulating layer, Tezuka et al., Journal of Applied Physi
cs, Vol. 79 (1996), No. 8, page 6262, "Mag
netic Tunneling effect in Fe / Al ₂ O ₃ / Ni _1-X Fe _X Junct
As described in "Ions", a method of spontaneously oxidizing Al, or the method of Moodera et al. 1997 Digests of INTERMAG '97,
"Large Magnetoresistancein Tunn" published in FA-04
el Junctions-Potential for MRAM and Read Head "
As described above, there is a method of exposing Al to oxygen plasma to oxidize it.

[0004]

In the method of forming an insulating layer by oxidizing Al as described above, it is necessary to form an Al layer on a magnetic layer. However, since the melting point of Al is low, it is difficult to form an Al layer having a uniform thickness even by using a sputtering method. Therefore, the thickness of the insulating layer obtained by oxidizing the Al layer becomes uneven. The non-uniformity of the thickness of the insulating layer has a problem that the magnetoresistance ratio of the multilayer film is reduced.

The present invention has been made in view of such a problem in the application of a multilayer film exhibiting a magnetic tunneling phenomenon to a magnetoresistive head. It is intended to provide a mold head.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies on a multilayer film exhibiting a magnetic tunneling phenomenon, and as a result, as an insulating layer, a metal oxide which is easily oxidized and has a relatively high melting point is used. The inventors have found that an insulating layer having a uniform thickness can be obtained by using the same, and have completed the present invention.

That is, the present invention relates to a magnetoresistive head using a multilayer film in which a first magnetic layer, an insulating layer, and a second magnetic layer are formed in this order, wherein the insulating layer is formed of a periodic table. IVa, Va group elements Ti, Zr, Hf, V, N
It is characterized by comprising an oxide of one element selected from the group of b and Ta or an oxide of an alloy composed of a plurality of elements. For the alloy, any combination of elements such as Hf-Zr and Nb-Ti can be used.

[0008] Ti, Zr, Hf, V, Nb and Ta are metals that are easily oxidized. Further, since the melting point is relatively high, a metal layer having a uniform thickness can be formed. Therefore, an insulating layer having a uniform thickness, a high tunnel barrier, and excellent insulating properties can be obtained. T
Among i, Zr, Hf, V, Nb, and Ta, Zr, N
b, Hf, and Ta are preferable because the atoms are large and diffusion with the magnetic layer hardly occurs. Further, Ti, Zr, and Hf are advantageous for forming a flat insulating layer because the metal layer tends to become amorphous. Further, Zr and Hf are most preferable because they are easily oxidized spontaneously and can be oxidized in a short time, and the oxide is stable and the tunnel barrier is hardly broken. However, Hf is disadvantageous in that it is expensive.

A structure may be employed in which an antiferromagnetic layer is in contact with the first magnetic layer or the second magnetic layer. Further, by changing the coercive force of the first magnetic layer and the second magnetic layer, only the magnetization of one of the magnetic layers may be reversed by the action of the leakage magnetic field from the recording magnetization. This magnetoresistive head can be combined with an inductive magnetic head. According to the present invention, since the thickness of the insulating layer can be made uniform, the reproducing output of the magnetoresistive head is high, and a magnetic head effective as a reproducing magnetic head of an ultra-high density magnetic recording device can be obtained. it can.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. [Embodiment 1] FIG. 1 is a schematic sectional view of an example of a magnetoresistive element of the present invention using a multilayer film. In the figure, a substrate 11 has a single crystal of Si (100) and a lower electrode 12.
Used was Au having a thickness of 10 nm. The ion beam sputtering method was used for forming the Au layer. The acceleration voltage of the ion gun for vapor deposition is 300 V, the ion current is 40 mA, and the Ar pressure during vapor deposition is 0.02 Pa. On the lower electrode 12, an insulator 13 having a square hole of 200 μm × 200 μm was formed by sputtering and lithography. The material of the insulator 13 is SiO ₂ .

Further, a magnetic layer 14 made of a 5 nm-thick Co layer was formed. The coercive force of the magnetic layer 14 is 800 A / m
It is. Ti, Zr, Hf, V, N on the magnetic layer 14
After preparing six types of samples each having a 2.0 nm thick metal layer made of b and Ta, the samples were once taken out to the atmosphere. By exposing the sample to the atmosphere for 24 hours,
An oxide of the above metal was formed to form an insulating layer 15. As the magnetic layer 16, a Ni-20 at% Fe alloy layer having a thickness of 5 nm was used. The coercive force of the magnetic layer 16 is 80 A / m, and the anisotropic magnetic field is 400 A / m.

As a comparative example, a 2.0 nm thick A
Insulating layer 1 also oxidized by exposing
5 was also formed. Each of these layers was also formed by an ion beam sputtering device. The sputtering conditions are the same as those for forming the lower electrode. As shown in FIG.
The multilayer films 14, 15, 16 are also formed on the insulator 13. However, since these portions are not in contact with the lower electrode 12, they do not function as a magnetoresistive film. Only the portion in contact with the lower electrode 12 functions as a magnetoresistive film. Further, as shown in FIG. 1, an upper electrode 17 made of Au having a thickness of 20 nm was formed on the multilayer film.

Table 1 shows the magnetoresistance ratio of the formed multilayer film. The magnetoresistance ratio was measured by applying a magnetic field between -80 kA / m and +80 kA / m back and forth to the multilayer film.
In this multilayer film, since the coercive forces of the two magnetic layers 14 and 16 are different, the angle between the directions of magnetization changes between parallel and antiparallel. As a result, the tunneling probability of electrons tunneling through the insulating layer 15 changes and a magnetoresistance effect occurs. In addition, the magnetoresistance ratio shown in Table 1 is an average value obtained by measuring 10 samples.

[0014]

[Table 1] As can be seen from Table 1, the multilayer film of the comparative example using the insulating layer obtained by oxidizing Al has a relatively low magnetoresistance ratio. This is because the flatness of the formed Al layer is poor, there are thin portions and thick portions, and the magnetic layers 14 and 16 are formed by pinholes.
This is because a short circuit may occur. In contrast, Ti,
When the Zr, Hf, V, Nb, and Ta layers are oxidized,
The magnetoresistance ratio is high. This is considered to be because the insulating layers having a uniform thickness were formed due to the good flatness of these layers. [Embodiment 2] FIG. 2 is a schematic sectional view of another example of a magnetoresistive element of the present invention using a multilayer film. In the figure, a substrate 21 has a single crystal of Si (100) and a lower electrode 22.
Used was Au having a thickness of 10 nm. The ion beam sputtering method was used for forming the Au layer. The forming conditions are the same as in the first embodiment. On the lower electrode 22, 200
An insulator 23 having a square hole of μm × 200 μm was formed by sputtering and lithography. The material of the insulator 23 is SiO ₂ .

Further, a Ni-20 at% F having a thickness of 5 nm is used.
The magnetic layer 24 made of e was formed. T on the magnetic layer 24
thickness 2.0n consisting of i, Zr, Hf, V, Nb, Ta
After preparing six types of samples each having m metal layers formed thereon, the samples were once taken out to the atmosphere. The oxide of the above metal was formed by exposing the sample to the air for 24 hours, and the insulating layer 25 was formed. The magnetic layer 26 has a 5 nm-thick Ni-
A 20 at% Fe alloy was used, and a 10 nm thick Mn-22 at% Ir alloy was used for the antiferromagnetic layer 27 in contact with the magnetic layer 26.

As a comparative example, a 2.0 nm thick A
A multilayer film using the insulating layer 25 obtained by oxidizing 1 was also formed. Each of these layers was also formed by an ion beam sputtering device. The sputtering conditions are the same as those for forming the lower electrode. As shown in FIG.
27 are formed. However, these parts are lower electrode 2
2 does not function as a magnetoresistive film. The lower electrode 22 functions as a magnetoresistive film.
Only the part in contact with Further, as shown in FIG. 2, an upper electrode 28 made of Au having a thickness of 20 nm was formed on the multilayer film.

Table 2 shows the magnetoresistance ratio of the formed multilayer film. The magnetoresistance ratio was measured by applying a magnetic field of −40 kA / m to +40 kA / m back and forth to the multilayer film. In this multilayer film, since the magnetic layer 26 is in contact with the antiferromagnetic layer 27, only the magnetization direction of the magnetic layer 24 changes, and the angles formed by the magnetizations of the two magnetic layers 24 and 26 are parallel and antiparallel. Change between. Therefore, the tunneling probability of the electrons tunneling through the insulating layer 25 changes, and the magnetoresistance effect occurs. In addition, the magnetoresistance ratio shown in Table 2 is an average value obtained by measuring 10 samples.

[0018]

[Table 2] As can be seen from Table 2, the multilayer film of the comparative example using the insulating layer obtained by oxidizing Al has a relatively low magnetoresistance ratio. This is because the flatness of the formed Al layer is poor, there are thin portions and thick portions, and the magnetic layers 24 and 26 are formed by pinholes.
This is because a short circuit may occur. In contrast, Ti,
When the Zr, Hf, V, Nb, and Ta layers are oxidized,
The magnetoresistance ratio is high. This is considered to be because the insulating layers having a uniform thickness were formed due to the good flatness of these layers. [Embodiment 3] A magnetic head was manufactured using a magnetoresistive element of the type described in Embodiment 2. In this case, the hole of the insulator is a square of 5 μm × 5 μm.
The structure of the magnetic head is shown below. FIG. 3 is a perspective view in which a part of the recording / reproducing separation type head according to the present embodiment is cut away. The portion where the magnetoresistive element 31 is sandwiched between the shield layers 32 and 33 functions as a reproducing head, and the portions of the lower magnetic pole 35 and the upper magnetic pole 36 which sandwich the coil 34 function as a recording head.

Hereinafter, a method of manufacturing the head will be described. A
A sintered body mainly composed of l ₂ O ₃ .TiC was used as a slider substrate 37. A Ni—Fe alloy formed by a sputtering method was used for the shield layer and the recording magnetic pole. The thickness of each magnetic film was as follows. Upper and lower shield layers 32, 33
Is 1.0 μm, the lower magnetic pole 35 and the upper magnetic pole 36 are 3.0 μm.
m, Al ₂ O ₃ formed by sputtering was used as a gap material between the respective layers. The thickness of the gap layer was 0.2 μm between the shield layer and the magnetoresistive element, and 0.4 μm between the recording magnetic poles. Further, the distance between the reproducing head and the recording head was about 4 μm, and this gap was also formed of Al ₂ O ₃ . Cu having a thickness of 3 μm was used for the coil 34.

A magnetic disk drive was manufactured using the above magnetic head. 4A and 4B show the structure of the magnetic disk drive. FIG. 4A is a plan view, and FIG. 4B is a sectional view taken along the line AA '. The magnetic recording medium 41 rotated by the magnetic recording medium driving unit 42 has Co-Ni-P having a residual magnetic flux density of 0.75T.
A material composed of a t-Ta alloy was used. The track width of the magnetic head 43 held by the magnetic head driving unit 44 was 5 μm.

The reproducing magnetoresistive element used in the magnetic head of this embodiment has a higher reproduction output than the conventional magnetoresistive element, but also has a larger noise. Therefore, when a signal having a certain value or more is detected by the recording / reproducing signal processing system, the signal is recorded on the magnetic recording medium. The tunneling type magnetoresistive element is
It has a high magnetoresistance change rate and is effective as a reproducing magnetic head for an ultra-high density magnetic recording device. The problem of high noise could be avoided by the method described above.

According to the present invention, the read output is almost tripled as compared with the case where an Al oxide film is used as an insulating film, and a magnetic head capable of coping with high recording density and an ultra-high density incorporating the magnetic head are provided. A magnetic recording device can be obtained.

[0023]

As described above, in a magnetoresistive head using a multilayer film formed in the order of a magnetic layer, an insulating layer and a magnetic layer, the insulating layer is made of Ti, Zr, Hf, V, N
By using oxides of b and Ta, the thickness of the insulating layer becomes uniform, and the output of the magnetoresistive head increases. Further, a high-performance magnetic recording / reproducing apparatus can be obtained by using the above-mentioned magnetoresistive head.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an example of a magnetoresistance effect element according to the present invention.

FIG. 2 is a schematic cross-sectional view of another example of the magnetoresistive element of the present invention.

FIG. 3 is a perspective view showing the structure of a magnetic head used in the magnetic recording / reproducing apparatus of the present invention.

FIG. 4 is a diagram showing the structure of a magnetic disk drive.

[Explanation of symbols]

11, 21 ... substrate, 12, 22 ... lower electrode, 13, 23
... Insulator, 14, 16, 24, 26 ... Magnetic layer, 12, 2
5: insulating layer, 17, 28: upper electrode, 27: antiferromagnetic layer, 31: magnetoresistive element, 32, 33: shield layer, 34: coil, 35: lower magnetic pole, 36: upper magnetic pole,
37: substrate, 41: magnetic recording medium, 42: magnetic recording medium drive, 43: magnetic head, 44: magnetic head drive,
45 Recording / reproduction signal processing system

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noboru Shimizu 1-280 Higashi Koigabo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (56) References JP-A-10-190092 (JP, A) JP-A-11 -168249 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B 5/39

Claims (4)

(57) [Claims] A first NiFe alloy layer, an insulating layer, a second
In a magnetoresistive head using a multilayer film formed in the order of a NiFe alloy layer, the insulating layer is made of Ti,
An oxide of one element selected from the group of V, Ta, or
Selected from the group of Ti, V, Ta, Zr, Hf, Nb
A magnetoresistive head comprising an oxide of an alloy comprising a plurality of elements . 2. The magnetoresistive head according to claim 1, wherein an antiferromagnetic layer is in contact with the first magnetic layer or the second magnetic layer. 3. A magnetic head comprising a combination of the magnetoresistive head according to claim 1 and an inductive magnetic head. 4. A magnetic recording and reproducing apparatus comprising the magnetic head according to claim 1, 2, or 3.