Patent ID: 7310210

Claim:
A magnetoresistive sensor comprising: a pinned layer having a magnetization direction fixed with respect to an external magnetic field; a free layer, having a magnetization direction variable in accordance with the external magnetic field; and a spacer layer mainly containing copper, sandwiched between said pinned layer and said free layer, wherein a sense current flows through said pinned layer, said spacer layer, and said free layer substantially in a direction in which said layers are stacked, and wherein said free layer comprises: at least one intermediate stack having a non-magnetic layer mainly containing copper, and first cobalt iron layers made of a cobalt iron alloy and disposed on boundaries on both sides of said non-magnetic layer; nickel iron alloy layers disposed on boundaries on both sides of said intermediate stack; a second cobalt iron layer made of a cobalt iron alloy and formed in contact with said spacer layer on a boundary of a stack composed of said intermediate stack and said nickel iron alloy layers, said boundary opposing said spacer layer; and a third cobalt iron layer including a cobalt iron alloy and formed on the other surface of said stack, wherein said first cobalt iron layers each have a cobalt atomic percent in a range from 65% to 75%, said second cobalt iron layer has a cobalt atomic percent in a range from 65% to 75%, and said third cobalt iron layer has a cobalt atomic percent in a range from 65% to 75%, and wherein said first cobalt iron layers each have a thickness in a range from 0.2 nm to 1.0 nm, said second cobalt iron layer has a thickness in a range from 0.5 nm to 1.5 nm, and said third cobalt iron layer has a thickness in a range from 0.5 nm to 1.5 nm.