Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-07-16
2003-11-11
Ometz, David L. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06646834
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a magnetic transducer and a thin film magnetic head using the same. More particularly, the invention relates to a magnetic transducer capable of improving thermal stability and obtaining a high exchange coupling magnetic field, a thin film magnetic head using the same, a method of manufacturing a magnetic transducer and a method of a manufacturing a thin film magnetic head.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in a surface recording density of a hard disk or the like. A composite thin film magnetic head, which has a stacked structure comprising a reproducing head having a magnetoresistive element (hereinafter referred to as an MR element) that is a type of magnetic transducer and a recording head having an inductive magnetic transducer, is widely used as the thin film magnetic head.
MR elements include an AMR element using a magnetic film (an AMR film) exhibiting an anisotropic magnetoresistive effect (an AMR effect), a GMR element using a magnetic film (a GMR film) exhibiting a giant magnetoresistive effect (a GMR effect), and so on.
A reproducing head using the AMR element is called an AMR head, and a reproducing head using the GMR element is called a GMR head. The AMR head is used as the reproducing head having a surface recording density exceeding 1 Gbit/inch
2
(0.16 Gbit/cm
2
), and the GMR head is used as the reproducing head having a surface recording density exceeding 3 Gbits/inch
2
(0.47 Gbit/cm
2
).
As the GMR film, a “multilayered type (antiferromagnetic type)” film, an “inductive ferromagnetic type” film, a “granular type” film, a “spin valve type” film and the like are proposed. Of these types of films, the spin valve type GMR film is considered to have a relatively simple structure, to exhibit a great change in resistance even under a low magnetic field and to be suitable for mass production.
FIG. 19
shows a structure of a general spin valve type GMR film (hereinafter referred to as a spin valve film). A surface indicated by reference symbol S in
FIG. 19
corresponds to a surface facing a magnetic recording medium. The spin valve film has a stacked structure comprising an underlayer
501
, a soft magnetic layer
502
, a nonmagnetic layer
503
, a ferromagnetic layer
504
, an antiferromagnetic layer
505
and a cap layer
506
, which are stacked in this order on the underlayer
501
. In the spin valve film, the orientation of magnetization Mp of the ferromagnetic layer
504
is fixed by exchange coupling between the ferromagnetic layer
504
and the antiferromagnetic layer
505
, whereas the orientation of magnetization Mf of the soft magnetic layer
502
freely changes according to a signal magnetic field, and thus the resistance of the spin valve film changes according to a relative angle between the orientation of the magnetization Mp of the ferromagnetic layer
504
and the orientation of the magnetization Mf of the soft magnetic layer
502
.
Currently, the size reduction of the MR element is advancing for a hard disk or the like having an extra-high recording density, but a smaller MR element results in a higher current density of a current passing through the spin valve film, and therefore, high thermal stability is required for the spin valve film.
In U.S. Pat. No. 5,828,529, disclosed is a spin valve film having the so-called synthetic pin structure comprising a coupling layer (an AF coupling film) made of ruthenium (Ru) inside a ferromagnetic layer. In U.S. Pat. No. 5,828,529, it is reported that thermal stability is improved through the adoption of the synthetic pin structure.
However, the above-mentioned U.S. Pat. No. 5,828,529 gives no report about specific improvements in thermal stability. To obtain stable resistance characteristics, it is necessary to increase an exchange coupling magnetic field to be generated between a ferromagnetic layer and an antiferromagnetic layer, but the above-mentioned U.S. Pat. No. 5,828,529 gives no report about the exchange coupling magnetic field.
SUMMARY OF THE INVENTION
The invention is designed to overcome the foregoing problems. It is an object of the invention to provide a magnetic transducer capable of improving thermal stability and obtaining a high exchange coupling magnetic field, a thin film magnetic head using the same, a method of manufacturing a magnetic transducer and a method of a manufacturing a thin film magnetic head.
A magnetic transducer of the invention comprises a stack including: a nonmagnetic layer having a pair of surfaces; a soft magnetic layer formed on one surface of the nonmagnetic layer; a ferromagnetic layer formed on the other surface of the nonmagnetic layer, the ferromagnetic layer having an inner ferromagnetic layer, a coupling layer and an outer ferromagnetic layer, which are stacked in this order on the nonmagnetic layer; and an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the nonmagnetic layer, wherein an average crystal particle diameter of at least one of a surface, interfacing with the coupling layer, of the inner ferromagnetic layer and a surface, interfacing with the coupling layer, of the outer ferromagnetic layer lies between 3 nm and 8 nm inclusive.
Another magnetic transducer of the invention comprises a stack including: a nonmagnetic layer having a pair of surfaces; a soft magnetic layer formed on one surface of the nonmagnetic layer; a ferromagnetic layer formed on the other surface of the nonmagnetic layer, the ferromagnetic layer having an inner ferromagnetic layer, a coupling layer and an outer ferromagnetic layer, which are stacked in this order on the nonmagnetic layer; and an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the nonmagnetic layer, wherein at least one of the inner ferromagnetic layer and the outer ferromagnetic layer has an average crystal particle diameter of from 3 nm to 8 nm inclusive in a direction perpendicular to a stacking direction of the stack.
In a magnetic transducer or another magnetic transducer of the invention, the average crystal particle diameter of at least one of the inner ferromagnetic layer and the outer ferromagnetic layer lies between 3 nm and 8 nm inclusive, so that the interface between the coupling layer and at least one of the inner and outer ferromagnetic layers becomes flattened, and therefore the thermal stability improves, and the exchange coupling magnetic field increases.
Preferably, the stack includes a crystal-growth inhibitor layer, which is located at least one of on a side close to the antiferromagnetic layer and on a side close to the soft magnetic layer with respect to the coupling layer and is made of a material containing at least one element in a group consisting of O (oxygen), N (nitrogen), H (hydrogen), Cu (copper), Au (gold), Ag (silver) and Rh (rhodium). More preferably, the crystal-growth inhibitor layer is dispersedly formed in the direction perpendicular to the stacking direction of the stack. Preferably, the inner ferromagnetic layer and the outer ferromagnetic layer are made of a material containing at least Co in a group consisting of Co (cobalt) and Fe (iron). Preferably, the coupling layer is made of a material containing at least one element in a group consisting of Ru (ruthenium), Rh, Re (rhenium) and Cr (chromium).
A thin film magnetic head of the invention comprises: a stack including a nonmagnetic layer having a pair of surfaces, a soft magnetic layer formed on one surface of the nonmagnetic layer, a ferromagnetic layer formed on the other surface of the nonmagnetic layer, and an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the nonmagnetic layer; and a base for supporting the stack, wherein the ferromagnetic layer has an inner ferromagnetic layer, a coupling layer and an outer ferromagnetic layer, which are stacked in this order on the nonmagnetic layer, and an average crystal particle diame
Araki Satoru
Sano Masashi
Tsuchiya Yoshihiro
Uesugi Takumi
Ometz David L.
TDK Corporation
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