Growth of high quality single crystals of skutterudite compound containing uranium

A Skutterrudite compound containing an uranium element, UFe4P12, was synthesized as a single crystal by a tin flux method. High quality of the single crystal was confirmed by x-ray Laue patterns and NMR spectrum of 31P nuclei. A ferromagnetic phase transition was observed at about 3 K by temperature dependence of magnetization. Magnetic moment of uranium estimated from susceptibility measurements at high temperatures was found to be 2.2μB, which was smaller than the values expected from trivalent or tetravalent uranium. This smaller value indicated that f electrons in uranium were in a state of a largely splitting energy level caused by a crystalline field or in an itinerant state. (Y. Kazumata)