Magnetic structures of α-MnS and MnSe from57Fe Mossbauer spectroscopy

57 Fe Mossbauer spectroscopy is used to investigate the low-temperature behaviours of alpha -MnS and MnSe, and the results are successfully interpreted in terms of a crystal field model. In alpha -MnS there are at least two magnetic spin arrangements. At 131K<T<T N the spins are along a cubic (110) direction, whereas at T<117K a multiaxial arrangement is likely. MnSe is found to exhibit two distinct crystallographic structures which coexist at certain temperatures. In a NaCl form the spin arrangement is multiaxial. The other form is a NiAs modification, in which the spins are along a hexagonal (210) direction.