Theory on the giant magnetoresistance in magnetic layered structures at finite temperatures

The temperature dependence of the giant magnetoresistance (GMR) in M1/N/M2 multilayers, consisting of magnetic Mi (i = 1, 2) and non-magnetic N layers, is discussed using the finite temperature band theory in which the effect of spin fluctuations is taken into account by the static functional integral method. When the temperature is increased, the magnetoresistance (MR) ratio (ΔRR) decreases in the normal MR, but increases in the inverse MR where the MR ratio is negative, although its absolute magnetude decreases. In a multilayer, where normal and inverse MRs coexist, ΔRR may show a maximum vs. temperature. In the compensated MR, the temperature coefficient of ΔRR becomes small because of the cancellation between the two contributions over a fairly wide temperature range; this could be beneficial for practical applications.