MOSSBAUER SPECTROSCOPIC STUDY OF FEAL1-XCOX

We report the results of a Mossbauer study of the alloy system FeAl1-x Cox for x greater-than-or-equal-to 0.3 at temperatures down to 83 K. M agnetic splitting is observed for x greater-than-or-equal-to 0.35 at a ll temperatures. However, for x = 0.3, no splitting is observed at roo m temperature, and superparamagnetic behavior occurs at LN2 temperatur e. The magnetically split spectra are fitted each with a distribution of hyperfine fields and the average hyperfine field B(hf)BAR as a func tion of temperature is obtained. The variation of B(hf)BAR with T is e xplained using the model of magnetic clusters with collective magnetic excitations from which the saturation hyperfine field and the magneti c anisotropy energy for these clusters are obtained. Also, the results are discussed using the model of random atomic distributions, and the agreement between the calculated and the experimentally obtained dist ributions of hyperfine fields is found improve as x increases.