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IP.com Disclosure Number: IPCOM000010136D
Original Publication Date: 2002-Oct-24
Included in the Prior Art Database: 2002-Oct-24
Document File: 1 page(s) / 39K

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We disclose a dual CPP sensor using AP-Coupled free layer to generate larger magnetoresistance. The structure is as follows:

Shield 1/PtMn/CoFe(1)/Ru/CoFe(2)/Al2O3/CoFe/Ru/CoFe/Al2O3/CoFe(3)/Ru/CoFe(4)/Ta/Shield 2

The current flows perpendicular to the plane of the layers. Shields also act as the electrodes supplying current as well as detection electrodes. PtMn layer is only about < 30A and act as the seed layer for the growth of rest of the sensor structure. The pinned ferromagnetic layers: CoFe(1)/Ru/CoFe(2) and CoFe(3)/Ru/CoFe(4) are SELF-PINNED. The SELF-PINNING is achieved through the perpendicular stress induced anisotropy caused by compressive stress at the air bearing surface and positive magnetostriction of the CoFe. The layers CoFe(1) and CoFe(3) are thicker than layers CoFe(2) and CoFe(4). In-addition, the composition of CoFe can be selected to provide larger stress induced anistropy for CoFe(1)/CoFe(3) as compared to CoFe(2)/CoFe(4) or vice versa. This dHk difference or thickness difference allows these layers to be properly oriented, i.e., the magnetization of layer CoFe(2) making 180 degree angle relative to the magnetization of layer CoFe(3) so that the signal adds from top/bot sensors. The layers between the Al2O3 barriers form the AP_Coupled Free layer where magnetization of the two ferromagnetic films are always 180 degree out of phase.

It is understood that the magnetizations of the two ferromagnetic...