Magnetic Excitations in Semiconducting SmS

Abstract

Inelastic neutron scattering measurements of the ${\mathrm{Sm}}^{2+}$, $^{7}F_{0}\ensuremath{\rightarrow}^{7}F_{1}$ singlet-triplet exciton dispersion in semiconducting SmS at 77, 197, and 273\ifmmode^\circ\else\textdegree\fi{}K are reported. The results are in good agreement with current theory predicting the temperature dependence of the singlet-triplet excitations. The $^{7}F_{0}\ensuremath{-}^{7}F_{1}$ separation is found to be (420 \ifmmode\pm\else\textpm\fi{}2)\ifmmode^\circ\else\textdegree\fi{}K, in agreement with the free-ion value of 422\ifmmode^\circ\else\textdegree\fi{}K, while the exchange interactions are characteristic of a magnetic semiconductor. The implications for the Sm-ion eigenstate are discussed.