Positive giant magnetoresistance in ferrimagnetic/Cu/ferrimagnetic films

Spin valves composed of ferrimagnetic/Cu/ferrimagnetic layers were fabricat ed with the magnetization perpendicular to the film planes. By changing the composition of ferrimagnetic layers, both negative and positive giant magn etoresistance (GMR) can be observed in ferrimagnetic spin valves. For sampl es consisting of both transition-metal (TM-) rich TbFeCo and GdFeCo, negati ve GMR values were obtained. Due to the high resistivity of amorphous ferri magnetic films, the shunting effect of Cu led to relatively small MR ratio. The negative MR effect was 1% for 1.7 nm Cu. For spin valves consisting of rare-earth (RE-)rich TbFeCo and TM-rich GdFeCo, positive GMR values were o bserved. A thin layer of Co was inserted between RE-rich TbFeCo and Cu to m anipulate the sign of GMR. (C) 2001 American Institute of Physics.