Dynamic magnetic information storage or retrieval – Head – Hall effect
Patent
1996-09-23
1998-05-12
Tupper, Robert S.
Dynamic magnetic information storage or retrieval
Head
Hall effect
G11B 539
Patent
active
057515212
ABSTRACT:
A spin valve sensor structure for a magnetic read head is provided which employs first and second spin valve sensors separated by an insulative gap layer. Each spin valve sensor has a spacer layer sandwiched between a pinned layer and a laminated free layer. The magnetic orientations of the pinned layers are pinned in the same direction by first and second antiferromagnetic layers. The first laminated free layer includes a very thin ruthenium (Ru) layer sandwiched between first and second ferromagnetic free layers and the second laminated free layer includes a second very thin ruthenium (Ru) layer sandwiched between third and fourth ferromagnetic free layers. The second ferromagnetic free layer is thicker than the first ferromagnetic free layer and the third ferromagnetic free layer is thicker than the fourth ferromagnetic free layer. Upon the application of a magnetic field, the magnetic moments of the second and third ferromagnetic free layers rotate and the magnetic moments of the first and fourth ferromagnetic free layers follow due to strong exchange coupling. A first spacer layer is sandwiched between the first pinned layer and the second ferromagnetic free layer so that these layers produce a spin valve effect, and the second spacer layer is sandwiched between the second pinned layer and the fourth ferromagnetic free layer so that these layers produce a spin valve effect. Since the magnetic moments of the second and fourth ferromagnetic free layers are antiparallel, their rotations, relative to the direction of the magnetic moments of the pinned layer, produce responses of opposite polarity when excited by a magnetic field of one polarity. The opposite polarity responses are fed to a differential amplifier where they are combined for enhanced signal output and common mode noise rejection.
REFERENCES:
patent: 5408377 (1995-04-01), Gurney et al.
patent: 5442508 (1995-08-01), Smith
patent: 5576915 (1996-11-01), Akiyama et al.
patent: 5583725 (1996-12-01), Coffey et al.
International Business Machines - Corporation
Tupper Robert S.
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