Temperature variation of the magnetoresistance in cobalt-enhanced spin-valve structures

We have conducted a survey of the temperature variation of the magnetoresistance in a series of FeMn exchange-biased spin-valve structures. These permalloy-based samples were prepared in an ion-beam sputtering system and feature Co layers inserted at the interfaces with the Cu spacer layer to enhance the interfacial spin-dependent scattering. Typical values for the MR are 4.0% at 295 K and 8.4% at 8 K (sample with 15 Angstrom Co thickness). A control sample with no cobalt showed MR values of 1.3% and 4.3% for those same temperatures. Both the MR ratio and the un-normalized magnetoresistive change Delta R are plotted vs temperature. The MR ratio for the cobalt-enhanced samples exhibits nearly linear decrease with rising temperature. The sample with no cobalt exhibits a temperature variation deviating substantially from linearity, with an upward curvature. The temperature dependence for the MR in these spin valves is examined in the light of interchannel spin-mixing and intrachannel scattering. (C) 1997 American Institute of Physics.