Magnetic Excitations in Semiconducting SmS

Abstract

Inelastic neutron scattering measurements of the ${\mathrm{Sm}}^{2+}$, ${}_{}{}^7{}_{}{}^{}F_0^{}{}_{}{}^{}\to {}_{}{}^7{}_{}{}^{}F_1^{}{}_{}{}^{}$ singlet-triplet exciton dispersion in semiconducting SmS at 77, 197, and 273°K are reported. The results are in good agreement with current theory predicting the temperature dependence of the singlet-triplet excitations. The ${}_{}{}^7{}_{}{}^{}F_0^{}{}_{}{}^{}-{}_{}{}^7{}_{}{}^{}F_1^{}{}_{}{}^{}$ separation is found to be (420 ±2)°K, in agreement with the free-ion value of 422°K, while the exchange interactions are characteristic of a magnetic semiconductor. The implications for the Sm-ion eigenstate are discussed.