Magnetic study of two isotypic manganese chloro-sulfides: MnSbS2Cl and the new compound MnBiS2Cl
Résumé
Among the MnPnQ2X compounds (Pn: pnictide; Q: chalcogen; X: halogen), two isotypic chloro-sulfides, MnSbS2Cl and MnBiS2Cl, have been studied. MnBiS2Cl is a new compound synthesized by solid state reaction at 500 1C. It is orthorhombic, space group Pnma, with a ¼ 9:502ð2Þ, b ¼ 3:8802ð8Þ, c ¼ 12:305ð3Þ A˚ , V ¼ 453:7ð2Þ ˚A3, Z ¼ 4. Its X-ray single crystal study shows (001) waved layers of MnS4Cl2 octahedra, opposite edge-sharing along b, and corner-sharing along a. Similar magnetic susceptibilities for both compounds have been recorded, indicating high spin Mn2+ with anti-ferromagnetic exchange. Correlatively, specific heat versus temperature shows a magnetic transition at TN ¼ 35K for the Sb-bearing compound, and a two-steps magnetic transition at 28 and 32K for the Bi isotype. The magnetic structure of MnSbS2Cl has been determined by neutron diffraction, revealing a magnetic ordering at 1.5K with an incommensurate wave-vector along b (k ¼ [0, 0.3838, 0]). Two modulation models, sinusoidal and helicoidal, give quite equivalent reliability factors (Rmag ¼ 0:0573 and 0.0586, respectively).