EFFECT OF SMALL VARIATIONS OF THE Fe/Cr RATIO ON THE 57Fe MOESSBAUER SPECTRA OF FeCr2S4.

By varying the Fe/Cr ratio in FeCr//2S//4, it is found that a slight excess of Fe has a substantial effect on the Moessbauer spectra, while a small deficit has virtually no effect. The paramagnetic spectra of Fe//1//. //0//6Cr//1//. //9//4S//4 show the superposition of a singlet and a doublet, the latter being attributed to Fe**2** plus on A sites having one nearest neighbor B-site Cr**3** plus replaced by an Fe**2** plus . A lambda-type peak in the heat capacity of Fe//0//. //9//7Cr//2S//4 is observed at 9. 25 K, indicative of the cooperative antiferrodistortive Jahn-Teller transition observed earlier with Moessbauer spectroscopy.