Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
1999-04-13
2001-04-24
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S690000, C428S690000, C428S394000, C428S690000, C428S690000, C428S900000, C324S252000, C360S112000
Reexamination Certificate
active
06221518
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetoresistance effect film for reading the magnetic field intensity of a magnetic recording medium or the like as a signal and, in particular, to a magnetoresistance effect film which is capable of reading a small magnetic field change as a greater electrical resistance change signal, and further relates to a magnetoresistance effect type head using such a magnetoresistance effect film. They are mainly incorporated in, for example, hard disk drives so as to be used.
2. Description of the Prior Art
Recently, following the high densification of hard disks, highly-sensitive heads with high outputs have been demanded. In response to these demands, spin valve heads have been developed.
The spin valve head has a structure wherein two ferromagnetic layers are formed via a non-magnetic metal layer, and an antiferromagnetic layer is disposed so as to abut one of the ferromagnetic layers. The ferromagnetic layer abutting the antiferromagnetic layer is in exchange coupling to the antiferromagnetic layer so that the magnetization of the ferromagnetic layer is fixed (pinned) in one direction. The magnetization of the other ferromagnetic layer is freely rotated following the change of the external magnetic field. In the spin valve, the MR change is realized by a difference in relative angles of spins between the two ferromagnetic layers. Therefore, the exchange coupling between the antiferromagnetic layer and the ferromagnetic layer abutting thereto can be thought as the substance of the spin valve.
As a material of an antiferromagnetic layer used in the spin valve, FeMn, NiMn, PtMn or the like has been well known.
When FeMn is used as the antiferromagnetic layer, the exchange coupling is generated relative to the ferromagnetic layer immediately after the formation of a film. Thus, a heat treatment for generating the exchange coupling is not required after the film formation. However, there is raised a limitation in order of the film formation that the antiferromagnetic layer should be formed after the formation of the ferromagnetic layer. Further, when FeMn is used, there is a problem that a blocking temperature is low, i.e. about 150 to 170° C. The blocking temperature is a temperature at which the exchange coupling pinning a magnetic layer is lost.
On the other hand, when NiMn or PtMn is used as the antiferromagnetic layer, the blocking temperature is high, i.e. no lower than 300° C., and further, there is no limitation in order of the formation of the antiferromagnetic layer and the ferromagnetic layer. However, for generating the exchange coupling between the antiferromagnetic layer and the ferromagnetic layer, a heat treatment is required in the magnetic field after stacking both layers. This is because, for NiMn or PtMn to exhibit the antiferromagnetism, a CuAu-I type regular crystal structure having a face centered tetragonal (FCT) structure needs to be formed. The heat treatment in the magnetic field is normally carried out under a temperature condition of 250 to 350° C. The degree of exchange coupling tends to be increased as the temperature is raised. However, if the heat treatment at high temperatures is applied to the spin valve film, mutual diffusion at boundary film surfaces of the stacked layers forming the spin valve film is caused so that a magnetoresistance change ratio (MR ratio) being an important film characteristic of the spin valve film is lowered. Therefore, when the spin valve head is formed, the sensitivity becomes poor and the output becomes small. Further, since the mutual diffusion at the boundary film surfaces of the stacked layers is generated, it is necessary to set large the thickness of the laminate film forming the spin valve film for ensuring a desired spin valve film characteristic. Thus, a product can not be more compact. Further, since the heat treatment after the formation of the spin valve film is a process at high temperatures and for a long time, improvement has also been demanded from the viewpoint of energy and productivity.
SUMMARY OF THE INVENTION
The present invention has been made under these circumstances and has objects to provide a magnetoresistance effect film wherein, in a spin valve film having an antiferromagnetic layer made of a compound containing Mn and having a CuAu-I type regular crystal structure which requires a heat treatment for manifesting an antiferromagnetic characteristic, mutual diffusion in the laminate film is very small and the MR ratio is large, and further provide a magnetoresistance effect type head which is excellent in sensitivity and high in output when formed as a spin valve head. It is a further object of the present invention to provide a magnetoresistance effect film wherein a laminate film forming a spin valve film can be reduced in thickness to achieve a more compact product and wherein the energy loss is small and the productivity is high.
For accomplishing the foregoing objects, according to one aspect of the present invention, there is provided a spin valve type magnetoresistance effect film comprising a multilayered film including a non-magnetic metal layer, a ferromagnetic layer formed on one surface of the non-magnetic metal layer, a soft magnetic layer formed on the other surface of the non-magnetic metal layer, and an antiferromagnetic layer which is formed on a surface of the ferromagnetic layer remote from the other surface thereof abutting the non-magnetic metal layer so as to pin a direction of magnetization of the ferromagnetic layer, wherein the antiferromagnetic layer is made of a compound containing Mn and having a CuAu-I type regular crystal structure, and wherein the antiferromagnetic layer is subjected to a crystallization treatment by laser irradiation for showing antiferromagnetism.
According to another aspect of the present invention, there is provided a magnetoresistance effect type head comprising a magnetoresistance effect film, conductive films and electrode portions, wherein the conductive films are conductively connected to the magnetoresistance effect film through the electrode portions, wherein the magnetoresistance effect film is a spin valve type magnetoresistance effect film which comprises a multilayered film including a non-magnetic metal layer, a ferromagnetic layer formed on one surface of the non-magnetic metal layer, a soft magnetic layer formed on the other surface of the non-magnetic metal layer, and an antiferromagnetic layer which is formed on a surface of the ferromagnetic layer remote from the other surface thereof abutting the non-magnetic metal layer so as to pin a direction of magnetization of the ferromagnetic layer, wherein the antiferromagnetic layer is made of a compound containing Mn and having a CuAu-I type regular crystal structure, and wherein the antiferromagnetic layer is subjected to a crystallization treatment by laser irradiation for showing antiferromagnetism.
It is preferable that the crystallization treatment of the antiferromagnetic layer is carried out by applying the laser irradiation to a film surface of the antiferromagnetic layer upon completion of the formation thereof.
It is preferable that the antiferromagnetic layer is formed on a substrate and the laser irradiation is applied to the film surface of the antiferromagnetic layer to crystallize the antiferromagnetic layer so as to manifest an antiferromagnetic characteristic, and that the ferromagnetic layer, the non-magnetic metal layer and the soft magnetic layer are formed in the order named on the antiferromagnetic layer applied with the laser irradiation.
It is preferable that the soft magnetic layer, the non-magnetic metal layer, the ferromagnetic layer and the antiferromagnetic layer are formed on a substrate in the order named, and that the laser irradiation is applied to the film surface of the antiferromagnetic layer to crystallize the antiferromagnetic layer so as to manifest an antiferromagnetic characteristic.
It is preferable that the crystallization treatment of the antiferromagne
Araki Satoru
Morita Haruyuki
Kiliman Leszek
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
TDK Corporation
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