Patent ID: 6891368

Claim:
A magnetoresistive sensor device comprising a substrate, and a sensing portion and a signal processing circuit formed above said substrate with a resin film being disposed between said sensing portion and said signal processing circuit, wherein said sensing portion detects changes in a magnetic field induced by a moving body and further said sensing portion being located at a position for effectively detecting changes in a magnetic field induced by said moving body, said sensing portion comprising a magnetoresistive sensor element, wherein said sensing portion is constituted by a giant magnetoresistive sensor element, and wherein: 1) said giant magnetoresistive sensor element comprises magnetic layers mainly containing Ni, Fe and Co alternately laminated with nonmagnetic layers mainly containing Cu, wherein said magnetic layers satisfy an atomic compositional ratio represented by the following formula: Ni (1-x-y) Fe y Co x , where x≧0.7, y≦0.3, and (1-x-y)≦0.15, and said nonmagnetic layers satisfy an atomic compositional ratio represented by the following formula: Cu z A (1-z) , where A is any additive element other than Cu, and z≧0.9, wherein the thickness of said magnetic layers(tm) and said nonmagnetic layers(tn) satisfies the following conditions respectively: 10 Å<tm<25 Å and 18 Å<tn<25 Å, 2) said giant magnetoresistive sensor element has a periodically repeating structure comprising a laminated body of said magnetic layers laminated with said nonmagnetic layers as one unit thereof, wherein the repeating number(N) of said periodically repeating structure satisfies the following conditions: 10≦N≦40, 3) said giant magnetoresistive sensor element comprises a buffer layer disposed between said resin film and said magnetic layers or disposed between said resin film and said nonmagnetic layers, wherein the thickness of said buffer layer(tb) satisfies the following conditions: 10 Å<tb<80 Å.