Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-12-14
2003-10-14
Renner, Craig A. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S324120
Reexamination Certificate
active
06633466
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a magnetoresistive thin film head for use in hard disk drives (HDD) or other such magnetic recording apparatus which record signals on magnetic recording media in high density, and reproduce the signals therefrom; more specifically, a magnetoresisitive thin film head in which the free magnetic layer of magnetoresistive element is provided with stable and effective biasing magnetic fields, for yielding signals of reduced noise yet having a high reproducing sensitivity. The present invention relates also to a method for manufacturing the magnetoresistive thin film head.
BACKGROUND OF THE INVENTION
The needs for higher processing speed and greater recording capacity are growing among HDDs and other apparatus for recording signals on magnetic recording media. A considerable number of activities are observed for satisfying the needs. For the high density recording, HDDs employ a thin film head; in which an inductive head is used for recording signals, and a magnetoresistive head (MR head), or a giant MR head (GMR head), is used for reproducing signals.
A conventional thin film head is described below referring to drawings.
FIG. 16
is a perspective view showing the outline at the sliding surface of a conventional thin film head facing a recording medium.
FIG. 17
shows an outline front view of the thin film head.
A lower gap layer
162
of Al
2
O
3
, AlN, SiO
2
or other nonmagnetic insulating material is formed on a lower magnetic shield layer
161
made of a soft magnetic material such as Permalloy, a Co amorphous magnetic layer, an Fe alloy magnetic layer. On top of the upper surface, a magnetoresistive element
163
(an MR element or a GMR element, hereinafter both are collectively referred to as GMR element) is deposited, and a longitudinal biasing layer
164
is formed by a CoPt alloy or other such material at both the right and the left ends of the GMR element
163
. A lead layer
165
of conductive material such as Cu, Cr, Ta, etc. is provided on the upper surface of the longitudinal biasing layer
164
so that the lead layer
165
makes contact with a ridge line formed by the upper surface of the GMR element
163
and the end faces. The lead layer
165
may be disposed instead on the upper surface of the longitudinal biasing layer
164
SO that it covers part of the upper surface of the GMR element
163
. Next, an upper gap layer
166
is formed over the lead layer
165
and the exposed region of the GMR element
163
, using the same nonmagnetic insulating material as the lower gap layer
162
. Further on top of the upper gap layer
166
, an upper magnetic shield layer
167
is provided using the same soft magnetic material as the lower magnetic shield layer
161
. This completes the reproducing part
168
of a magnetoresistive head.
On the upper surface of the upper magnetic shield layer
167
, a recording gap layer
171
is formed using the same nonmagnetic insulating material as the lower gap layer
162
. An upper magnetic core
172
, which faces to the upper magnetic shield layer
167
via the recording gap layer
171
and makes contact with the upper magnetic shield layer
167
at the rear scene of
FIG. 16
, is provided in the form of a layer using a soft magnetic material. Between the upper magnetic shield layer
167
and the upper magnetic core
172
facing to each other with the interposing recording gap layer
171
, a coil
173
is provided electrically isolated from both the upper magnetic shield layer
167
and the upper magnetic core
172
. This completes the recording part
170
of a magnetoresistive thin film head. The upper magnetic shield layer
167
works as the shield for the reproducing part
168
and as the lower magnetic core of the recording part
170
.
Recording current supplied to the coil
173
generates recording magnetic fields in the recording gap layer
171
disposed between the upper magnetic core
172
and the upper magnetic shield layer
167
of the recording head
170
, for recording the signals on a magnetic recording medium. The reproducing head
168
detects signal magnetic fields from a magnetic recording medium storing the signals, and signals reproduced by the GMR element
163
in accordance with the resistance shift are taken out through the terminal of lead layer
165
.
FIG. 17
shows outline front view of the reproducing part in the vicinity of magnetoresistive element of the above-described thin film head. A lower gap layer
162
is provided on the upper surface of the lower magnetic shield layer
161
. On top of it, an antiferromagnetic layer
174
formed of a magnetic material such as IrMn, an FeMn alloy, a PtMn alloy, &agr;Fe
2
O
3
, or NiO; a pinning layer
175
formed of a magnetic material such as a NiFe alloy, Co, a CoFe alloy; a nonmagnetic conductive layer
176
formed of a nonmagnetic conductive material such as Cu; a free magnetic layer
177
formed of the same material as the pinning layer; and an upper cap layer
166
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
163
is provided.
A pair of longitudinal biasing layers
164
are formed at both ends of the GMR element
163
in physical contact with the slant end surfaces, and a pair of the right and the left lead layers
165
are provided on the longitudinal biasing layers. On top of them, an upper gap layer
166
is formed, followed by an upper magnetic shield layer
167
. Thus the reproducing part
168
of a magnetoresistive thin film head is completed. Gap length
179
of the reproducing part
168
represents a total sum in the thickness of the lower gap layer
162
, the GMR element
163
and the upper gap layer
166
. The gap length
179
is becoming smaller, so that it is capable of reproducing the short-wavelength signals of high density recording.
With the reproducing part of the above-configured thin film head, in order to be able to reproduce the short-wavelength signals stored in a magnetic recording medium, gap length of the reproducing part 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 the lower gap layer, the GMR element and the upper gap layer. The short distance means that the pair of longitudinal 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 which circumstance, magnetic fields of the longitudinal biasing layers easily escape to the lower magnetic shield layer or the upper magnetic shield layer. As a result, magnetic coupling between the longitudinal biasing layer and 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 noise generation increases. Thus it is difficult for a thin film head of the conventional structure to yield stable reproducing signals. The reduced width of recording track for the high-density recording brings about a minimized spacing between the pair of the right and the left longitudinal biasing layers. Under such a situation, if magnetic field of the longitudinal biasing layer is made stronger, the free magnetic layer of GMR element receives a too strong magnetic field from the longitudinal biasing layer. This leads to a problem that it makes it difficult for a free magnetic layer to change the magnetization direction in response to signal magnetic field; deteriorating sensitivity of the reproduction. Another still greater problem is that the magnetization direction of pinning layer is prone to assume the direction of track width by the influence of longitudinal biasing magnetic field.
SUMMARY OF THE INVENTION
The
Fukazawa Toshio
Sakaguci Masaya
Matsushita Electric - Industrial Co., Ltd.
RatnerPrestia
Renner Craig A.
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