Pb1−xCoxSnS3: Synthesis, structure, and magnetic properties of a series of quaternary chalcogenides

Abstract

Quaternary metal chalcogenides, Pb_1−xCo_xSnS₃ (x = 0.00, 0.10, 0.20, and 0.40), were synthesized from high purity elements at high temperature via sealed tube solid state synthesis method. All the compounds crystallised in the orthorhombic crystal system with Pnma space group. Single crystal study indicated that Co substitute at the Pb-site in Pb_1−xCo_xSnS₃ in a disordered manner. The structure of Pb_1−xCo_xSnS₃ compounds contains edge shared bi-octahedral chains of SnS₆ and zig-zag chains of (Pb/Co)S running along b-direction. XPS study indicates that cobalt exists as Co²⁺ while tin and sulphur remain as Sn⁴⁺ and S²⁻ respectively. Magnetic susceptibility studies on Pb_1−xCo_xSnS₃ (x = 0.1, 0.2 and 0.40) suggest ferromagnetic ordering below 125 K. The Pb/Co-S-Pb/Co bond angle (88.6°) in the Pb/Co-S chains is very close to 90° suggesting ferromagnetic ordering in these compounds, which corroborate the magnetic susceptibility results. As the amount of Co substitution increases, the magnetic susceptibility values gradually increases as evident from the M-T curves, which is attributed to substitution of more Co²⁺ at the non-magnetic Pb²⁺ site in Pb_1−xCo_xSnS₃. The M − H isotherms reveal saturation magnetic moment that is smaller than the expected value, possibly due to disorder of the magnetic ions in these compounds. However, neutron diffraction study is required to completely understand the detailed magnetic properties in these compounds.