Origin of the temperature dependence of the giant magnetoresistance in magnetic granular solids

The temperature dependence of the giant magnetoresistance (GMR) and magnetic properties have been measured for granular solid ${\mathrm{Co}}_{20}$ ${\mathrm{Ag}}_{80}$. From the measured GMR, we have derived the temperature dependence of the effective spin S’ of the magnetic scatterers experienced by the conduction electrons. It is found that S’ shares the same temperature dependence as the spontaneous magnetization ${\mathit{M}}_{\mathit{s}}$(T) over the whole temperature range (5–310 K) of our measurement. Our results suggest that the origin of the temperature dependence of GMR is the reduced magnetization as a result of spin-wave excitations in magnetic granules.