Thermal expansion anomalies at the magnetic transition temperatures of Au 4Mn and Au 2Mn

Abstract

Measurements of the thermal expansion and specific heat are carried out for the ferromagnetic ordered alloy Au 4Mn and the antiferromagnetic one Au 2Mn at temperatures including the Curie temperature T c and Néel temperature T N. The pressure effect on T C and T N is also measured. It is found that both Au 4Mn and Au 2Mn have positive exchange strictions and d T C/d p and d T N/d p are positive. The results are discussed in terms of the MnMn distance dependence of the exchange interactions in AuMn alloys.