Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2003-05-28
2004-06-22
Davis, David (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06754051
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a magnetoresistance (MR) apparatus, and more particularly, to a spin valve type transducer capable of reducing a reproducing gap to less than 0.1 &mgr;m.
As magnetic storage apparatuses have been developed in size and capacity, highly sensitive magnetoresistive (MR) transducers (heads) have been put into practical use (see: Robert P. Hunt, “A Magnetoresistive Readout Transducer ”, IEEE Trans. on Magnetics, Vol. MAG-7, No. 1, pp. 150-154, Mar. 1971). Since use is made of the anisotropy magnetoresistance (AMR) effect of NiFe alloy, these MR heads are called AMR heads.
Recently, more highly sensitive giant magnetoresistance (GMR) transducers (heads) which are called spin valve type transducers, have also been developed in order to achieve higher area recording density (see: Ching Tsang et al., “Design, Fabrication & Testing of Spin-Valve Read Heads for High Density Recording ”, IEEE Trans. on Magnetics, Vol. 30, No. 6, pp. 3801-3806, Nov. 1994). A typical spin valve type transducer includes a spin valve structure which is constructed by a free ferromagnetic layer, a pinned ferromagnetic layer and a non-magnetic conductive layer sandwiched by the free ferromagnetic layer and the pinned ferromagnetic layer, and a pinning ferromagnetic layer for pinning the magnetic domain of the pinned ferromagnetic layer. In the spin valve type transducer, the resultant response is given by a cosine of an angle between the magnetization directions of the free ferromagnetic layer and the pinned ferromagnetic layer.
A prior art spin valve type transducer is constructed by two magnetic shield layers, two gap layers (magnetic isolation layers) each adhered to the inside of one of the magnetic shield layers, a spin valve structure sandwiched by the gap layers, a permanent magnet layer provided at the sides of the spin valve structure to provide magnetic domain control over the free ferromagnetic layer in order to suppress the Barkhausen noise, and an electrode layer formed on the permanent magnet layer (see JP-A-10-162322 & JP-A-10-149513). This will be explained later in detail.
In the above-described prior art spin valve type transducer, however, since the spin valve structure is sandwiched by the two gap layers, the resolution of the transducer, i.e., a reproducing gap between the two magnetic shield layers cannot be less than 0.1 &mgr;m, which will be explained later.
Generally, a bit length for showing the density of bits on a medium is denoted by the number of inversions of magnetic fluxes per inch, i.e., kilo flux changes per inch (kFCI). For example, if the bit length is 200 kFCI, one inversion length is 125 nm and one period is 250 nm. Therefore, the reproducing gap 0.1 &mgr;m
(100
nm) is enough for 200 kFCI. Also, if the bit length is 400 kFCI, one inversion length is 62.5 nm and one period is 125 nm. Therefore, the reproducing gap 0.1 &mgr;m (100 nm) is also enough for 400 kFCI. On the other hand, if the bit length is 500 kFCI, one inversion length is 50 nm and one period is 100 nm, the reproducing gap 0.1 &mgr;m (100 nm) is insufficient for 500 kFCI.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a spin valve type transducer capable of reducing a reproducing gap to less than 0.1 &mgr;m.
According to the present invention, in a spin valve type transducer including two magnetic shield layers, a patterned magnetoresistance element is in direct contact with one of the magnetic shield layers. A permanent magnet layer and an electrode layer are formed on the sides of the patterned magnetoresistance element.
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Robert P. Hunt, “A Magnetoresistive Readout Transducer”, IEEE Transactions on Magnetics, vol. MAG-7, No. 1, Mar. 1971, pp. 150-154.
Tsang, et al., “Design, Fabrication & Testing of Spin-Valve Read Heads for High Density Recording”, IEEE Transactions on Magnetics, vol. 30, No. 6, Nov. 1994, pp. 3801-3806.
Davis David
McGinn & Gibb PLLC
TDK Corporation
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