TRANSPORT AND MAGNETIC-PROPERTIES OF GDAG

Measurements of the electrical resistivity (rho), thermoelectric power (S), temperature derivatives d rho/dT and dS/dT, thermal conductivity (K) and differential thermal analysis, have been made in GdAg single crystals over the temperature range 10-300 K. The electrical resistivi ty is analysed in terms of impurity, phonon and magnetic contributions . The behaviour of rho and d rho/dT near T-N = 132 K indicates that th e magnetic transition is not driven by an electronic (Fermi level) mec hanism, Spin fluctuation effects are observed up to T similar to 1.5T( N), in the transport, magnetic and thermal properties. However, they a ffect d rho/dT and dS/dT differently; whereas d rho/dT has a maximum a t T-N, followed by a minimum at T similar to 1.15T(N), dS/dT has only a minimum at T-N. The thermal conductivity exhibits a minimum at T-N, resulting from the competition between a decreasing electron mean free path (as T increases) and a linearly increasing electronic specific h eat. At low temperatures the transport properties indicate an anomalou s behaviour, marked by a sharp decrease in d rho/dT starting around 35 K, and anomalously large thermopower values going through a maximum a round 20 K (S similar to 18.5 mu V K-1).