Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of substrate or post-treatment of coated substrate
Reexamination Certificate
2002-09-10
2004-04-13
Pianalto, Bernard (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of substrate or post-treatment of coated substrate
C427S058000, C427S123000, C427S130000, C427S131000, C427S132000, C427S331000, C427S402000, C427S404000, C427S569000
Reexamination Certificate
active
06720036
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of production of a spin valve type giant magnetoresistive thin film, and more particularly, relates to a method of production of a high performance spin valve type giant magnetoresistive thin film suitable for a magnetic recording head of a hard disk drive.
2. Description of the Related Art
A spin valve type giant magnetoresistive thin film used for a magnetic recording head of a hard disk drive has a multilayer film structure comprised of a plurality of layers (or thin films) including an antiferromagnetic layer, a fixed magnetization layer, a nonmagnetic conductive layer, and a free magnetization layer. In the multilayer film structure of the spin valve type giant magnetoresistive thin film, the nonmagnetic conductive layer is formed between the fixed magnetization layer and the free magnetization layer so that the two are isolated by the nonmagnetic conductive layer. Further, since the antiferromagnetic layer is made to adjoin the fixed magnetization layer, the magnetic moment of the fixed magnetization layer is fixed in one direction by the exchange coupling with the antiferromagnetic layer. On the other hand, the magnetic moment of the free magnetization layer is freely rotated in accordance with the external magnetic field.
The spin valve type giant magnetoresistive thin film generates the so-called “giant magnetoresistive effect”, or the change of the electrical resistance due to the relative angle formed by the magnetic moment of the fixed magnetization layer and the magnetic moment of the free magnetization layer. The rate of change of the electrical resistance due to the giant magnetoresistive effect is called the “magnetoresistive ratio” (MR ratio). The MR ratio of a spin valve type giant magnetoresistive thin film is far higher than that of a conventional anisotropic magnetoresistive thin film.
There are three types of spin valve type giant magnetoresistive thin films. The first type, as shown in
FIG. 19
, is a so-called “bottom type” comprised, from a substrate
111
side, of a buffer layer
112
, an antiferromagnetic layer
113
, a fixed magnetization layer
114
, a nonmagnetic conductive layer
115
, a free magnetization layer
116
, and a protective layer
117
stacked consecutively in that order. The second type, as shown in
FIG. 20
, is a so-called “top type” comprised, from a substrate
111
side, of a buffer layer
112
, a free magnetization layer
116
, a nonmagnetic conductive layer
115
, a fixed magnetization layer
114
, an antiferromagnetic layer
113
, and a protective layer
117
stacked consecutively in that order. The third type, as shown in
FIG. 21
, is a so-called “dual type” comprised, from a substrate
111
side, of a buffer layer
112
, a first antiferromagnetic layer
113
A, a first fixed magnetization layer
114
A, a first nonmagnetic conductive layer
115
A, a free magnetization layer
116
, a second nonmagnetic conductive layer
115
B, a second fixed magnetization layer
114
B, a second antiferromagnetic layer
113
B, and a protective layer
117
stacked consecutively in that order.
In the above three types of spin valve type giant magnetoresistive thin films, in the past there have been proposed thin films replacing the single layers of the fixed magnetization layers
114
,
114
A, and
114
B with synthtic ferrimagnet structures comprised of fixed magnetization layer elements, nonmagnetic layers, and fixed magnetization layer elements (U.S. Pat. No. 5,465,185). Further, the free magnetization layer
116
also comes in single layer structures and multilayer structures. In free magnetization layers and fixed magnetization layers of multilayer structures, all the layers are magnetic films, but sometimes different magnetic films are stacked or a sandwich structure interposing a nonmagnetic film therebetween is used.
The giant magnetoresistive effect of the above spin valve type giant magnetoresistive thin film is due to spin-dependent scattering of conductive electrons at the stacked interfaces of multilayer films. Therefore, to obtain a high MR ratio, cleanliness or flatness of the interfaces becomes important in the process of production of the spin valve film. Therefore, in the spin valve type giant magnetoresistive thin film, to achieve the cleanliness or flatness of the interfaces, the films are often formed continuously in the same vacuum chamber so that the intervals between formations of one layer and another become as short as possible.
Techniques for forming a film in vacuum include magnetron sputtering, ion beam sputtering, electron cyclotron resonance (ECR) sputtering, facing target sputtering, high frequency sputtering, electron beam evaporation, resistance heating evaporation, molecular beam epitaxy (MBE), etc.
To obtain a high MR ratio, the thickness of the nonmagnetic conductive layer
115
should be small so as to suppress the flow of conductive electrons not contributing to the giant magnetoresistive effect (shunt effect). If the thickness of the nonmagnetic conductive layer
115
is made small, however, the fixed magnetization layer
114
and the free magnetization layer
116
will end up coupling ferromagnetically through the nonmagnetic conductive layer
115
. The interlayer coupling magnetic field (Hin) between the fixed magnetization layer and the free magnetization layer should be small for practical use of the magnetic recording head of a hard disk drive. A field of a value in the range of −10 to +10 Oe is preferable. In the past, to reduce the interlayer coupling magnetic field, the thickness of the nonmagnetic conductive layer
115
was set to a thick 2.5 to 3.5 nm.
Further, in the related art, the technique of reducing the ferromagnetic coupling occurring between the fixed magnetization layer and the free magnetization layer by inserting a nano oxide layer (NOL) of a size of not more than 1 nm into the fixed magnetization layer in the bottom type of spin valve film (Y. Kamiguchi et al.;
Digests of INTERMAG
'99, DB-01) has been proposed. As a result, a relatively small interlayer coupling magnetic field is obtained and a high MR ratio is obtained even with a thin (2 to 2.5 nm) nonmagnetic conductive layer.
That is, in the conventional spin valve type giant magnetoresistive thin film, the thickness of the nonmagnetic conductive layer was set thick (2.5 to 3.5 nm) to reduce the interlayer coupling magnetic field, but the problem arose of a flow of conductive electrons not contributing to the giant magnetoresistive effect (shunt effect) and the MR ratio ending up being reduced. Further, in the process of production of the above nano oxide layer, an oxidation step becomes necessary in the middle of formation of the fixed magnetization layer. An oxidation step is complicated and is poor in reproducibility.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of production of a spin valve type giant magnetoresistive thin film able to maintain a low interlayer coupling magnetic field and obtain a high MR ratio without the use of an oxidation step even when the nonmagnetic conductive layer is thin.
The method of production of the spin valve type giant magnetoresistive thin film according to the present invention is configured as follows in order to achieve the above object.
According to a first aspect of the present invention, there is provided a method of production of a spin valve type giant magnetoresistive thin film comprised of a buffer layer deposited on a substrate, a multilayer part comprised of a nonmagnetic conductive layer, a fixed magnetization layer and a free magnetization layer sandwiching this, and an antiferromagnetic layer formed adjoining the fixed magnetization layer, and a protective layer deposited at a topmost position, wherein at least one location in a plurality of interfaces formed between the nonmagnetic conductive layer and the buffer layer is treated by plasma. In the method of production of this spin valve type giant magnetoresistive thin film, a p
Nakajima Daisuke
Tsunekawa Koji
Anelva Corporation
Pianalto Bernard
LandOfFree
Method of production of spin valve type giant... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of production of spin valve type giant..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of production of spin valve type giant... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3230407