Synthesis, structure, magnetic and optoelectric properties of layered Na M 0.5 Sn 0.5 S 2 (M= Mn, Fe)

Two new layered sulfides, namely NaMn0.5Sn0.5S2 and NaFe0.5Sn0.5S2, have been successfully synthesized. Their structures were determined using single crystal X-ray diffraction. The two compounds crystallize in trigonal system with space group R3¯m. Their cell parameters are a = 3.7630 (5) Å, c = 19.896 (3) Å and a = 3.711(5) Å, c = 20.00(3) Å for NaMn0.5Sn0.5S2 and NaFe0.5Sn0.5S2, respectively. Light absorption measurements showed that band gap of NaMn0.5Sn0.5S2 and NaFe0.5Sn0.5S2 are 1.5 eV and 0.7 eV, respectively. Magnetization measurements showed that NaMn0.5Sn0.5S2 compound is paramagnetic from 2 K to 300 K with an effective moment of 6.4 μB per Mn2+ and a Weiss temperature Θp of −71 K NaFe0.5Sn0.5S2 undergoes an antiferromagnetic transition at TN = 14 K, with an effective moment of 4.5 μB per Fe2+ and a Weiss temperature Θp of −60 K. Heat capacity measurements showed that NaMn0.5Sn0.5S2 has a Debye temperature of 407.4 K and short range ordering at low temperature. The current density of NaFe0.5Sn0.5S2 increased from 0.2 mA⋅cm−2 to 0.3 mA cm−2 under illumination at a voltage bias of 5 V, indicating that it is a good photoelectric material.