THEORY OF THE TEMPERATURE-DEPENDENT GIANT MAGNETORESISTANCE IN MAGNETIC MULTILAYERS

The giant magnetoresistance (GMR) in magnetic multilayers at finite temperatures is studied with the use of the functional-integral method in the static approximation. Numerical calculations are performed by using a simple model. The effect of spin fluctuations is shown to play important roles in discussing the temperature-dependent GMR. The temperature dependence of the calculated GMR is much larger-than that of the magnetization, and it shows an almost linear decrease near the Curie temperature when the temperature is raised. It is also shown that the temperature dependence of the GMR is more significant in a multilayer with a larger ground-state GMR. Our calculation accounts well for the GMR feature observed in many transition-metal multilayers.