Valence transitions of Sm in monosulfide solid solutions

Magnetic-susceptibility and lattice-parameter measurements indicate that Sm in Sm1-xYxS for x>0.15, in Sm1-xLaxS for x>0.33, and in Sm1-xGdxS for x>0.17 is in an intermediate valence state at T=295 K. A transition from this intermediate valence state to a more divalent but still intermediate valence state is observed on cooling and on heating from room temperature in Sm1-xYxS for 0.15<x<0.27. For x>0.47, Sm remains intermediate valent on cooling to T=4.2 K and on heating to T=900 K. Its susceptibility is independent of temperature below T=100 K. Related effects are observed in the Sm1-xLaxS and in the Sm1-xGdxS systems. A model of interconfiguration fluctuations including multiple energy levels in both configurations and crystal-field effect may explain these results. © 1975 The American Physical Society.