A study of iron in gold–iron alloys

Gold–iron alloys (composition range 20 to 50 at% Fe) have been examined magnetically. In the as-quenched condition the value of the saturation magnetization appears to saturate at about 3.0 μB per iron atom if all the magnetic forces are attributed solely to the iron atoms. This high value for the number of Bohr magneton is discussed in terms of the nature of the iron in solution. The isothermal decomposition of one of the alloys, Au–38 at% Fe. was followed by the measurement of magnetic properties and by transmission electron microscope observations. The saturation magnetization decreased with ageing time to the expected equilibrium value. The apparent inverse dependence of the coercive force on temperature is interpreted as a magnetic short-circuit effect. Transmission electron microscopy reveals the heterogeneousprecipitation of a second phase in the form of platelets.