| 摘要 |
This invention provides a CPP TMR or GMR sensor with an amorphous ferromagnetic lower keeper layer and a crystalline ferromagnetic upper keeper layer. The amorphous ferromagnetic lower keeper layer strongly exchange-couples to an underlying antiferromagnetic pinning layer and planarizes its rough surface. The crystalline ferromagnetic upper keeper layer strongly antiparallel-couples to an adjacent ferromagnetic reference layer across a nonmagnetic spacer layer. The amorphous ferromagnetic lower keeper layer is preferably made of a Co—Fe—B alloy film with an Fe content high enough to ensure strong exchange-coupling to the underlying antiferromagnetic pinning layer, and with a B content high enough to ensure the formation of an amorphous phase for planarizing an otherwise rough surface due to the underlying antiferromagnetic pinning layer. The crystalline ferromagnetic upper keeper layer is preferably made of a Co—Fe alloy film with an Fe content low enough to ensure strong antiparallel-coupling to the adjacent ferromagnetic reference layer across the nonmagnetic spacer layer. The sensor is annealed at temperatures low enough to prevent the amorphous phase from transforming into a polycrystalline phase, but also high enough to maximize TMR.
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