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

Highlights: • ¹⁵¹Eu Mössbauer spectrum measurements were performed for EuLnBiS₄ (Ln = Eu, Gd). • These compounds show an antiferromagnetic transition at 2.8 and 6.5 K, respectively. • In Eu₂BiS₄, Eu²⁺ and Eu³⁺ ions occupy two crystallographically independent sites. - Abstract: Ternary and quaternary rare earth bismuth sulfides EuLnBiS₄ (Ln = Eu, Gd) have been investigated by X-ray diffraction, ¹⁵¹Eu Mössbauer 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 ¹⁵¹Eu Mössbauer 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.