Thin film head with transverse biasing layers

Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head

Reexamination Certificate

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Reexamination Certificate

active

06574080

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a magnetoresistive thin film head for use in hard disk drives (HDD) or such other magnetic recording apparatus which record signals on magnetic recording media in high density, and reproduce the signals therefrom; specifically, the magnetoresistive thin film head in which stable biasing magnetic fields are provided, on a free magnetic layer of a magnetoresistive element, for yielding a high reproducing efficiency. The present invention relates also to the method for manufacturing the magnetoresistive thin film head.
BACKGROUND OF THE INVENTION
The needs for higher processing speed and greater recording capacity are increasing among the magnetic disk apparatus (hereinafter collectively referred to as HDD) and other magnetic recording apparatus, and quite a number of efforts are being made for increasing the recording density. In order to meet the requirements for the higher density recording, the HDDs employ a thin film head, which head consisting of an inductive head for recording, and a magnetoresistive head (MR head), or a giant MR head (GMR head), for reproducing the signals.
A conventional thin film head is described below referring to FIG.
23
and FIG.
24
.
FIG. 23
is a perspective view showing outline at the sliding surface of a conventional thin film head facing a recording medium.
FIG. 24
shows an outline view of the thin film head in the front.
In
FIG. 23
, a lower gap layer
232
of Al
2
O
3
, AlN, SiO
2
, or other nonmagnetic insulating material is formed on a lower magnetic shield layer
231
made of a soft magnetic material such as Permalloy, a Co amorphous magnetic layer, an Fe alloy magnetic layer. On the upper surface of the lower gap layer
232
, a magnetoresistive element
233
(an MR element or a GMR element, hereinafter both are collectively referred to as GMR element) is deposited, and a transverse biasing layer
234
is formed by a CoPt alloy or other such magnetic material at both of the right and the left ends of the GMR element
233
. A lead layer
235
of conductive material such as Cu, Cr, Ta, etc. is provided on the upper surface of the transverse biasing layer
234
so that the lead layer
235
makes contact with a ridge line formed by the upper surface of the GMR element
233
and the end face. The lead layer
235
may be disposed on the upper surface of the transverse biasing layer
234
so that it covers part of the upper surface of the GMR element
233
. Next, an upper gap layer
236
is formed over the lead layer
235
and the exposed region of the GMR element
233
, using the same nonmagnetic insulating material as the lower gap layer
232
. Further on top of the upper gap layer
236
, an upper magnetic shield layer
237
is provided using the same soft magnetic material as the lower magnetic shield layer
231
. This completes the reproducing part
238
of magnetoresistive head.
On the upper surface of the upper magnetic shield layer
237
, a recording gap layer
241
is formed using the same nonmagnetic insulating material as the lower gap layer
232
. An upper magnetic core
242
, which faces to the upper magnetic shield layer
237
via the recording gap layer
241
and makes contact with the upper magnetic shield layer
237
at the rear scene of
FIG. 23
, is provided in the form of a layer using a soft magnetic material. Between the upper magnetic shield layer
237
and the upper magnetic core
242
facing to each other with the interposing recording gap layer
241
, a coil
243
is provided electrically isolated from both the upper magnetic shield layer
237
and the upper magnetic core
242
. This completes the recording part
240
of a magnetoresistive thin film head. The upper magnetic shield layer
237
works as the shield for the reproducing part
238
and as the lower magnetic core of the recording part
240
.
FIG. 24
shows outline view in the front of the reproducing part at the vicinity of magetoresistive element of the above-described thin film head. A lower gap layer
232
is provided on the upper surface of the lower magnetic shield layer
231
. On the lower gap layer
232
, an antiferromagnetic layer
244
formed of a magnetic material such as an FeMn alloy, a PtMn alloy, a pinning layer
245
formed of a magnetic material such as a NiFe alloy, Co, a CoFe alloy, a nonmagnetic conductive layer
246
formed of a nonmagnetic conductive material such as Cu, a free magnetic layer
247
formed of the same material as the pinning layer
245
, and a cap layer
248
formed of a nonmagnetic material such as Ta, are deposited sequentially. The laminated body of stacked layers is defined at both the right and the left ends by ion-milling or the like method so that each of the cut ends has a slant surface. Thus a GMR element
233
is provided. A pair of transverse biasing layers
234
are formed at both ends of the GMR element
233
in physical contact with the slant end surfaces, and a pair of the right and the left lead layers
235
are provided on the transverse biasing layers
234
. On top of them, an upper gap layer
236
is formed, followed by upper magnetic shield layer
237
. Gap length
249
of the reproducing part
238
, which represents a total sum in the thickness of the lower gap layer
232
, the GMR element
133
, and the upper gap layer
236
, takes a very small value, so that it is capable of reproducing the short-wavelength signals of high density recording.
Recording current supplied to the coil
243
generates recording magnetic fields in the recording gap layer
241
disposed between the upper magnetic core
242
and the upper magnetic shield layer
237
of the recording head
240
, for recording the signals on a magnetic recording medium. The reproducing head
238
detects signal magnetic fields from a magnetic recording medium storing the signals, and signals reproduced by the GMR element
233
in accordance with the resistance change are taken out through the terminal of lead layer
235
.
In order to be able to reproduce the short-wavelength signals stored in a magnetic recording medium, gap length of a reproducing head needs to be sufficiently short. As described earlier, the gap length is a distance between the upper surface of the lower magnetic shield layer and the lower surface of the upper magnetic shield layer. It means that the distance is represented by a total thickness of lower gap layer, the GMR element, and the upper gap layer. The short distance means that a pair of transverse biasing layers disposed at both the right and the left ends of the GMR element are existing very close to the lower magnetic shield layer or the upper magnetic shield layer. Under such circumstance, magnetic fields of the transverse biasing layers easily escape to the lower magnetic shield layer or the upper magnetic shield layer. Thus in a thin film head of the conventional structure, the biasing magnetic field, applied to the free magnetic layer of GMR element, becomes weak. And the direction of magnetization of the free magnetic layer is not orientated in a stable manner, and the noise increases, making it difficult to obtain stable reproducing signals.
SUMMARY OF THE INVENTION
The present invention addresses the above described drawbacks, and aims to make the orientation of magnetizing direction in the free magnetic layer stabilized, by providing the free magnetic layer of GMR element with accurate and stabilized biasing magnetic fields generated from the transverse biasing layers. By so doing, superior magnetoresistive head, having suppressed Barkhausen noise and superior reproducing characteristics, can be offered. The present invention also contains in it a method for manufacturing the magnetoresistive head.
The thin film head of the present invention comprises a magnetoresistive element formed of an antiferromagnetic layer, a pinning layer, a nonmagnetic conductive layer and a free magnetic layer, and a pair of the right and the left laminated transverse biasing layers, each consisting of a nonmagnetic layer, a ferromagnetic layer and an antiferromagnetic la

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