ANTIFERROMAGNETIC BEHAVIOR OF A NOVEL SINGLE-CRYSTAL URANIUM COMPOUNDU2.67TE4

Single crystals of the uranium compound U2.67Te4 were grown by slow co oling of a material of similar composition after melting it in a carbo n resistance furnace at temperatures ranging from 1450 to 1540 degrees C. The crystal structure of U2.67Te4 was determined from single-cryst al X-ray diffraction data and refined to a residual value R=0.037. Thi s compound crystallizes in the cubic Th3P4-type structure with the lat tice parameter a=9.4000 Angstrom. The phase composition of the crystal s has also been determined using energy-dispersive analysis by X-rays. The results were found to be in reasonable agreement with the diffrac tion X-ray data. The magnetic susceptibility of a few U2.67Te4 single crystals has been measured within the temperature range 4.2-300 K. At T=20 K the magnetic susceptibility goes through a maximum, which can i ndicate an antiferromagnetic transition. The magnetic susceptibility a bove 25 K could be fitted with a Curie-Weiss law. The effective magnet ic moment and the paramagnetic Curie temperature are mu(eff)=3.29 mu(B ) per U atom and theta(p)=2.1 K respectively.