Pressure-induced Novel Electronic State of Fe70Ni30 Invar Alloy

Abstract

The electrical resistance and magnetoresistance of Fe70Ni30 Invar alloy have been measured at high pressure up to 15GPa. It is found that the coefficients of T2 term in the electrical resistance increases with increasing pressure but tends to saturate above 12GPa suggesting a peak above 15GPa, which implies a pressure-induced quantum phase transition. We found for the first time that the magnetoresistance at 4.2K is negative below 11GPa but becomes positive above 12GPa. This corresponds to a crossover in the electronic state from localized moment regime to a paramagnetic or new magnetic state. The origins will be discussed briefly in connection with the recent experimental results and theoretical calculation.