TEMPERATURE-DEPENDENCE OF THE NORMAL AND INVERSE MAGNETORESISTANCE IN MAGNETIC MULTILAYERS

The temperature dependence of the giant magnetoresistance (GMR) in M1/N/M2 multilayers consisting of magnetic Mi (i=1,2) and nonmagnetic N layers, is discussed with the use of the finite-temperature band theory in which the effect of spin fluctuations is taken into account by means of the static functional-integral method combined with the coherent potential approximation. It is shown that the temperature dependence of the MR ratio, ΔR/R, shows a variety of behaviors depending on the values of a1 and a2 where ai=Δi/Δi and Δis is the imaginary part of the coherent potential of an s-spin electron at the interface of the Mi layer. In the normal MR where a1>1 and a2>1 (or a1<1 and a2<1), ΔR/R decreases as the temperature is raised. On the contrary, in the inverse MR where a1>1,a2<1 (or vice versa) and ΔR/R<0, it increases although its absolute magnitude decreases. In a multilayer where normal and inverse MR's coexist, ΔR/R may show a maximum or almost constant behavior in a fairly wide temperature range. © 1995 The American Physical Society.