Dynamic magnetic information storage or retrieval – Head – Hall effect
Patent
1995-05-15
1996-12-10
Psitos, Aristotelis
Dynamic magnetic information storage or retrieval
Head
Hall effect
360135, 360 55, 365173, 428694R, G11B 5127, G11B 576, G11B 566, G11C 1115
Patent
active
055837271
ABSTRACT:
A magnetic recording data storage system uses a medium substrate with multiple data layers formed on it and a magnetoresistive (MR) read sensor that provides a direct digital output as it reads data in all the data layers simultaneously. In one disk drive embodiment, the magnetic recording disk is a conventional disk substrate with two magnetically isolated and decoupled magnetic data layers formed on it. Data is written into each of the data layers independently by appropriate selection of the coercivity of the magnetic materials used in the data layers and the strength of the write current in an inductive write head. In one embodiment for independently writing to any of the data layers, the data layers are made of magnetic materials having different coercivity vs. temperature dependencies, and the disk is heated (or not heated) prior to writing with a write field that affects only one of the data layers. The magnetic field strength from written data in each of the data layers is different from that of the other data layers so that the data can be distinguished by the MR read sensor. The preferred MR read sensor for the multiple data layer disk is a multilayer of alternating ferromagnetic layers and nonferromagnetic metal spacer layers based on the giant magnetoresistive (GMR) effect. However, in the present GMR sensor each ferromagnetic layer has its magnetic moment responsive to an external magnetic field strength that is different from the magnetic field strengths at which the magnetic moments of the other ferromagnetic layers are responsive. This allows each ferromagnetic layer in the GMR sensor to switch its magnetization direction from parallel to antiparallel, or vice versa, independently of the other ferromagnetic layers.
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Berthold Thomas R.
International Business Machines - Corporation
Neal Regina Y.
Psitos Aristotelis
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