Synthesis and magnetic studies of ternary germanides U3Co4Ge7 and U3Co2Ge7

Abstract

U3Co4Ge7 and U3Co2Ge7 have been prepared as single crystals by solution growth from tin flux. U3Co4Ge7 crystallizes in the tetragonal structure (I4/mmm) with lattice parameters a = 0,4116 nm and c = 2,749 nm and U3Co2Ge7 possesses the orthorhombic structure (Cmmm) with a = 0,4151 nm, b = 2,498 nm, c = 0,4160 nm. All measurements document ferromagnetism in U3Co4Ge7 below TC = 21 K. The magnetization and magnetic susceptibility measurements revealed strong magnetocrystalline anisotropy. The c-axis has a strong ferromagnetic contribution to the magnetization and was found to be the easy-magnetization direction. U3Co2Ge7 shows onset of magnetic ordering at 41 K. The b-axis is the easy magnetization direction with the saturated magnetization μat = 1 μB/U at 2 K. The magnetization curves show anomalous behavior; the virgin curve goes far out of the hysteresis loop and reaches higher value of saturated magnetization.