Abstract
Inelastic-neutron-scattering methods have been used to measure the spin-wave spectrum in EuO and EuS over the entire Brillouin zone. The samples were polycrystalline powders enriched in . Defining the interaction between pairs of spins to be , we obtained for EuO, °K and °K; for EuS, °K and °K. The measured Curie temperatures for EuO, 69.15 ± 0.05°K, and for EuS, 16.57 ± 0.01 °K, are in excellent agreement with calculated values obtained from series expansions relating to the exchange constants. In EuO, the neutron scattering measurements determine and separately. Although separate values for the exchange constants were reported in earlier experiments, we show that in fact only the spin-wave stiffness constant of EuO, which is proportional to , was actually determined. In EuS, our values of and agree with a reanalysis of the specific-heat data.
- Received 13 May 1976
DOI:https://doi.org/10.1103/PhysRevB.14.4897
©1976 American Physical Society