JPH08329424A - Magnetoresistance effect head and magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE: To suppress Barkhausen noise and to obtain a device of high performance by decreasing the width of a magnetic circuit than the longitudinal length of a multilayered film. CONSTITUTION: A pair of magnetic path composed of Ni-Fe alloy are brought into contact with the end part of a multilayered film 11. The direction 13 of the magnetic flux is orthogonal to the longitudinal direction of the multilayered film 11. The width of the magnetic path 12 is narrower than the longitudinal length of the multilayered film 11. An electrode 14 composed of Cu is in contact with the multilayered film 11 while the electrode 14 is parallel to the magnetic path 12. In this case, the longitudinal length of the multilayered film 11 is 4μm, the width of the magnetic path 12 is 2μm and the width of the electrode 14 in contact with the multilayered film 11 is 1.5μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive effect element, a magnetic head and a magnetic recording / reproducing apparatus using a multilayer film having a high magnetoresistive effect.

[0002]

2. Description of the Related Art As the magnetic recording density increases, a material having a high magnetoresistive effect is required as a magnetoresistive effect material used for a reproducing magnetic head. 1988, Baibic
Physical Review Letters (Pysica
l Review Letters), Vol. 61, No. 21, 2472-
See "Giant Magnetoresistance of (00) Fe / (001) Cr magnetic superlattice" on page 2475.
1) Fe / (001) Cr Magnetic Superlattices) ”,
In a magnetic film (Fe / Cr multilayer film) having a multilayer structure,
A magnetoresistance change rate (at 4.2K) of about 50% is reported.

[0003]

The Ni-Fe / Cu multilayer film having a structure similar to the above Fe / Cr multilayer film has a relatively high magnetoresistance change rate, but a magnetoresistive effect element using the multilayer film. However, there is a problem that Barkhausen noise similar to that of the conventional magnetoresistive effect element is generated.

An object of the present invention is to provide a method of suppressing Barkhausen noise in a magnetoresistive effect element using a multilayer film.

[0005]

The present inventors have found that the magnetic layer,
As a result of earnest studies on a magnetoresistive element using a multilayer film in which non-magnetic layers are laminated, it is shown that Barkhausen noise is suppressed by applying a magnetic field and a sense current only to the central portion of the multilayer film. Heading out, the present invention has been completed.

That is, in a magnetoresistive effect element comprising a multilayer film in which magnetic layers and nonmagnetic layers are alternately laminated, a magnetic path for applying a magnetic field to the multilayer film, and a pair of electrodes, By making the width narrower than the length in the longitudinal direction of the multilayer film, the movement of the magnetic domain wall at the end of the multilayer film in which a large number of domain walls are generated is suppressed, and the width of the pair of electrodes is set to the longitudinal direction of the multilayer film. By making the width narrower than this, the change in the electrical resistivity of the central portion of the multilayer film in which the domain wall is less likely to occur is detected.

[0007]

As a result, Barkhausen noise of the magnetoresistive effect element using the multilayer film is suppressed. Further, because of the structure as described above, the magnetoresistive effect element does not directly contact the magnetic recording medium, and noise due to heating does not occur. Also,
The magnetoresistive effect element is suitable for a magnetic head or the like,
Further, by using the above magnetic head, a high performance magnetic recording / reproducing apparatus can be obtained.

[0008]

【Example】

Example 1 A plan view of a magnetoresistive effect element of the present invention is shown in FIG.
Shown in A pair of magnetic paths 12 made of a Ni—Fe alloy is brought into contact with the ends of the multilayer film 11. The magnetic flux direction 13 is perpendicular to the longitudinal direction of the multilayer film. The width of the magnetic path 12 is the multilayer film 1
1 is smaller than the length in the longitudinal direction. Electrode 14 made of Cu
Contacts the multilayer film 11 in parallel with the magnetic path 12. In this embodiment, the length of the multilayer film 11 in the longitudinal direction is 4 μm, and the magnetic path 12 is
Has a width of 2 μm, and the width of a portion of the electrode in contact with the multilayer film is 1.5 μm.

FIG. 2 shows a sectional structure of the multilayer film 11. The method for forming this multilayer film will be described below. First, a 5 nm-thick Ni—O-based buffer layer 22 was formed on a glass substrate 21 using an ion beam sputtering apparatus. Although NiO was used as the sputtering target, it is considered that the composition of the buffer layer formed by sputtering deviates from the stoichiometric composition. The sputtering conditions are an Ar pressure of 0.02 Pa, an ion gun acceleration voltage of 900 V, and an ion current of 120 mA. The substrate on which the above-mentioned Ni-O-based buffer layer was formed was once taken out from the ion beam sputtering apparatus, and again,
Returned to the device.

Further, a Ni-Fe-Co magnetic layer 23 having a thickness of 1.5 nm and a Cu non-magnetic layer 24 having a thickness of 2.3 nm were alternately laminated on the Ni-O system buffer layer 22. The number of magnetic layers 23 is 10. Sputtering conditions are Ar pressure 0.02 Pa, ion gun acceleration voltage 3
The voltage is 00 V and the ion current is 40 mA. Ni-Fe-Co
The sputtering target for forming the magnetic layer is Ni-
An alloy target having a composition of 16 at% Fe-18 at% Co was used. A magnetic field was applied during the formation of the multilayer film. Therefore, the easy magnetization direction exists in the longitudinal direction of the multilayer film 11 of FIG.

The above magnetoresistive element of the present invention is processed to expose the end portion of the magnetic path, the magnetic path is brought into contact with a prerecorded floppy disk, the floppy disk is rotated, and the recorded signal is detected. did. As a result of producing 20 devices in total and reproducing the signals, 16 devices showed good characteristics without Barkhausen noise.

When a magnetic field was applied to the above-mentioned element using a Helmholtz coil and the magnetic field / voltage curve was measured, 10 elements produced Barkhausen noise. When a magnetic field is applied using the Helmholtz coil, the magnetic field is applied uniformly to the multilayer film. As a result, it is considered that the magnetic flux also entered the edges of the multilayer film where many domain walls were generated, and the domain walls moved. On the other hand, in the experiment using the above-mentioned floppy disk medium, the magnetic flux passes through the magnetic path and enters the multilayer film. Therefore, the magnetic flux is mainly applied to the central portion of the multilayer film. Therefore, it is considered that Barkhausen noise is reduced because the domain wall at the end of the multilayer film is hard to move.

Further, due to the above structure, the sense current also flows intensively in the central portion of the multilayer film, and the sense current is less likely to flow in the end portions of the multilayer film where many domain walls are generated. Therefore, it is considered that the magnetoresistive effect element mainly detects the change in the magnetization in the central portion of the multilayer film.

Further, because of the above-described structure, the magnetoresistive effect element does not directly contact the magnetic recording medium, and noise due to heating does not occur.

When a conventional material having an anisotropic magnetoresistive effect is used as the magnetoresistive effect material, the magnetoresistive effect is produced depending on the direction of the sense current and the direction of magnetization. For this reason,
In the above-mentioned element structure in which the sense current direction is parallel to the magnetic flux direction, a magnetoresistive effect having a sign different from that of the conventional magnetoresistive effect element is produced. On the other hand, the multilayer film that does not utilize the anisotropic magnetoresistive effect has little influence on the direction of the sense current, and is extremely advantageous for the magnetoresistive element having the structure of the present invention.

Example 2 A magnetic head was manufactured using the magnetoresistive effect element of the present invention. Al ₂ O ₃ · Ti on the substrate
A sintered body containing C as a main component was used. The magnetoresistive effect element was sandwiched between two layers of shield layers made of a Ni—Fe alloy.
The thickness of the shield layer was 1 μm. The gap between the shield layer and the magnetoresistive effect element was made of Al ₂ O ₃ . The thickness is 0.2 μm. A bias magnetic field from a permanent magnet was applied to the multilayer film in the magnetic field detection direction.

The gap between the shield and the induction type magnetic head was also made of Al ₂ O ₃ . The thickness is about 4 μm.
The magnetic poles of the induction type magnetic head were made of a Ni-Fe alloy. The thickness is 3.0 μm. The gap between the pair of recording magnetic poles was also formed of Al ₂ O ₃ . The thickness was 0.4 μm.
Moreover, Cu having a thickness of 3 μm was used for the coil. In addition, as a comparative example, a Ni-F film having a thickness of 40 nm is used instead of the multilayer film.
A magnetic head using an e-based alloy single layer film was also manufactured.

When recording / reproducing was performed with the magnetic head having the above-mentioned structure, a reproducing output 2.7 times higher than that of the magnetic head using the Ni--Fe single layer film was obtained. It is considered that this is because the magnetic head of the present invention uses a multilayer film having a high magnetoresistive effect. Also, no large noise was found in the reproduced waveform. This is considered to be an effect of the structure of the present invention.

<Embodiment 3> Using the magnetic head of the present invention described in Embodiment 2, a magnetic disk device was manufactured. A schematic diagram of the device is shown in FIG. For the magnetic recording medium 71, a material made of a Co—Ni—Pt—Ta alloy having a residual magnetic flux density of 0.75T was used. The track width of the magnetic head 73 is 3 μm
And The magnetoresistive effect element in the magnetic head 73 is
Since the reproduction output is high, a high-performance magnetic disk device which does not burden the signal processing was obtained.

[0020]

A multilayer film in which magnetic layers and non-magnetic layers are alternately laminated, and a magnetic path for applying a magnetic field to the multilayer film,
And a magnetoresistive effect element including a pair of electrodes,
By making the width of the magnetic path narrower than the length of the multilayer film in the longitudinal direction, the movement of the magnetic domain wall at the end of the multilayer film where a large number of domain walls are generated is suppressed, and the width of the pair of electrodes is set to the longitudinal direction of the multilayer film. By making the width narrower than this, the change in the electrical resistivity of the central portion of the multilayer film in which the domain wall is less likely to occur is detected. As a result, Barkhausen noise of the magnetoresistive effect element using the multilayer film was suppressed. Further, because of the structure as described above, the magnetoresistive effect element does not directly contact the magnetic recording medium, and noise due to heating does not occur. Further, the magnetoresistive effect element is suitable for a magnetic head and the like, and by using the magnetic head, a high performance magnetic recording / reproducing apparatus can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view of the structure of a magnetoresistive effect element according to the present invention.

FIG. 2 is a cross-sectional view showing the structure of a multilayer film used in the magnetoresistive effect element of the present invention.

FIG. 3 is an explanatory diagram of a magnetic recording / reproducing apparatus of the present invention.

[Explanation of symbols]

11 ... Multilayer film, 12 ... Magnetic path, 13 ... Direction of magnetic flux, 14 ...
electrode.

Claims (4)

[Claims] 1. A magnetoresistive effect element comprising a multilayer film in which magnetic layers and nonmagnetic layers are alternately laminated, a magnetic path for applying a magnetic field to the multilayer film, and a pair of electrodes. The longitudinal direction is perpendicular to the direction of the magnetic flux flowing in the magnetic path, the direction of the sense current flowing from the pair of electrodes to the multilayer film is parallel to the direction of the magnetic flux flowing in the magnetic path, and the width of the magnetic path is the multilayer. A magnetoresistive effect element, characterized in that it is narrower than the length of the film in the longitudinal direction, and the width of the pair of electrodes is narrower than the length of the multilayer film in the longitudinal direction. 2. A magnetoresistive head comprising the magnetoresistive element according to claim 1 and a shield layer. 3. A composite magnetic head in which the magnetoresistive head according to claim 2 and an inductive magnetic head are combined. 4. A magnetic recording / reproducing apparatus using the magnetic head according to claim 2 or 3.