Synthesis, structure, magnetic and photoelectric properties of Ln3M0.5M′Se7 (Ln = La, Ce, Sm; M = Fe, Mn; M′ = Si, Ge) and La3MnGaSe7

Abstract

Six new isostructural compounds, with the formulas La₃Fe_0.5GeSe₇, La₃MnGaSe₇, Ce₃Fe_0.5SiSe₇, Ce₃Mn_0.5SiSe₇, Sm₃Fe_0.5SiSe₇ and Sm₃Mn_0.5GeSe₇, have been successfully synthesized via a molten salt method. Their structures are determined by single crystal X-ray diffraction and they crystallize in the Ce₆Al_3.33S₁₄ structure type (space group: P6₃, Pearson symbol: hP24). Pure phases of the Ce₃Fe_0.5SiSe₇, Ce₃Mn_0.5SiSe₇, Sm₃Fe_0.5SiSe₇ and Sm₃Mn_0.5GeSe₇ compounds were obtained by solid state reaction and were characterized by powder X-ray diffraction (PXRD), scanning electron microscope (SEM), ultraviolet-visible-infrared (UV-vis-IR) absorbance spectroscopy, and magnetization measurements. The Ce₃Fe_0.5SiSe₇ and Ce₃Mn_0.5SiSe₇ compounds show paramagnetic domination accompanied by antiferromagnetic contributions, while the Sm₃Mn_0.5GeSe₇ and Sm₃Fe_0.5SiSe₇ compounds show anti-ferromagnetic phase transitions with Néel temperatures of 13 K and 24 K, respectively. Optical measurements reveal that all of the four compounds can absorb most of visible light. These four compounds also show photoelectric properties with the photocurrent densities of 81, 1.3, 1.8 and 0.8 μA cm⁻², respectively.