Abstrakt
U3Co4Ge7 and U3Co2Ge7 have been prepared as single crystals by the solution growth method from tin flux and studied by X-ray diffraction, magnetic, transport, and specific-heat measurements; ab initio electronic-structure calculations have also been performed to study magnetism theoretically. U3Co4Ge7 has a tetragonal structure (I4/mmm), while U(3)Co(2)G(e)7 crystallizes in en orthorhombic structure (Cmmm), which appears to be a distortion of a tetragonal structure.
All measurements document ferromagnetism in U3Co4Ge7 below T-C = 21 K with a strong magnetocrystalline anisotropy. The c-axis has a strong ferromagnetic contribution to magnetization and was found to be the easy-magnetization direction.
U3Co2Ge7 orders magnetically below 40 K; the magnetic structure is sensitive to the ratio a/c approximate to 1, e. g., the deviation from the tetragonal axis.