Magnetism, Metal‐Insulator Transition, and Optical Properties in Sm‐ and Some Other Divalent Rare‐Earth Monochalcogenides

摘要: In Sm2+X compounds (X = S, Se, Te) an unusualy large dependence of the low‐temperature Van Vleck susceptibility on ligand has been observed. SmSe, SmTe, and also TmTe undergo a continuous insulator‐metal transition under pressure. contrast, SmS shows discontinuous to metal at 6.5 kbar. all cases is accompanied by volume change around 20%, which due promotion 4f electron into 5d‐6s conduction band. Optical spectroscopy yields three distinct absorption peaks. They may be interpreted as transitions from 4f6↔4f55dt2g 4f6↔4f55deg probably excitonic peak. The activation energy found 0.63, 0.46, 0.20, 0.22 eV for SmS, TmTe, respectively, both pressure‐dependent electrical resistivity room temperature observed edge.