Magnetic Ordering in Gold-Iron Alloys

In an attempt to characterize the magnetic ordering in AuFe alloys, systematic studies were made of the temperature dependences of the thermoelectric power S and the low-field magnetic susceptibility for Fe concentrations C from 1 to 22 at. %. The concentration dependences of the magnitude and temperature of the maximum in S (T) showed transitions clearly related to the magnetic ordering. Data analyses based on molecular field theories indicate the existence of small regions of short-range ferromagnetic order which undergo longrange interactions as the temperature is lowered. For C12 at. %, long-range ferromagnetism is dominant. Lower-concentration alloys (C12 at. %) exhibit an antiferromagnetism with some properties similar to those of a magnetic spin-glass, but with well-defined ordering temperatures characterized by sharp cusps in (T), and with a negative Curie for C=1 and 2 at. %. These properties indicate a more perfect antiferromagnetic order than that expected for a random alloy or a spin-glass, and this may be related to preferred local lattice arrangements in these alloys.