Magnetic and 151Eu Mossbauer spectroscopic studies on rare earth bismuth sulfides, EuLnBiS4 (Ln = Eu, Gd)

Ternary and quaternary rare earth bismuth sulfides EuLnBiS(4) (Ln = Eu, Gd) have been investigated by X-ray diffraction, Eu-151 Mossbauer spectroscopy, and magnetic susceptibility measurements. Both compounds have the orthorhombic CaFe2O4-type structure with space group Pnma. In Eu2BiS4, Eu2+ and Eu3+ ions occupy two crystallographically independent sites. The Eu-151 Mossbauer spectra for Eu2BiS4 indicate that the Eu2+ and Eu3+ ions exist in the molar ratio of 1:1, and the Debye temperatures of Eu2+ and Eu3+ are 175 and 230 K, respectively. Magnetic susceptibility measurements for Eu2BiS4 and EuGdBiS4 reveal that an antiferromagnetic transition occurs at 2.8 and 6.5 K, respectively.