Spin glass to Kondo transition

Abstract

Recent theoretical results for the resistivity in the spin glass regime of alloys, like AuFe, are reviewed. New results are then presented that extend the theory into the Kondo regime at very low concentrations of magnetic (Fe-) atoms. A sharp transition between a Spin Glass and a Kondo phase is found. The singular point is at zero temperature and leads to observable critical behavior at low temperatures. The transition can be effected by changing the concentration or by applying pressure. The theory is shown to account well for the observed resistivity in a number of different alloy systems over a wide range of concentrations, pressures, and temperatures, including a resistivity maximum in both phases. Special emphasis is on new high-pressure observations in the transitional regime by Schilling and others. These results lead to a better understanding of the competition between spin glass and Kondo effects, and offer an opportunity to unify these hitherto separate physical ideas.