Hyperfine interactions in mixed valence Yb3S4

We have measured the hyperfine interactions in the semiconducting heavy-fer mion compound Yb3S4 using Yb-170 Mossbauer absorption and Yb-172 perturbed angular correlation spectroscopy in a wide temperature range. In the parama gnetic phase (T > 1.2 K), the temperature dependence of the electric field gradient indicates the presence of both Yb2+ and Yb3+ charge states. Below 1.2 K, the Yb3+ ions order magnetically with a saturated Yb3+ moment of 1 m u(B). (C) 1999 Elsevier Science B.V. All rights reserved.