Abstract
Lattice constants of MnO and MnS have been measured as a function of temperature from 7 to 300°K. Below the Néel temperature, the fcc lattices undergo a trigonal distortion as well as a volume contraction. By subtracting the usual thermal expansion from this volume contraction, the isotropic exchange striction has been studied. For MnO below the Néel temperature (K), good agreement with the randomphase Green's-function theory previously developed to describe sublattice magnetization is obtained for the trigonal distortion; on the other hand, for the volume contraction, there are no theoretical results available for the region immediately below the Néel temperature to compare with the experimental next-nearest-neighbor spin-correlation curve which has been obtained. For MnS, below the observed trigonal distortion was found to be a contraction along the [111] direction; the magnetization curves suggest, but do not positively prove, the absence of a biquadratic-exchange effect.
- Received 21 April 1969
DOI:https://doi.org/10.1103/PhysRevB.1.236
©1970 American Physical Society