Giant anisotropic magnetoresistance and magn etothermopower in cubic3:4 uranium pnictides

摘要

Temperature dependence of the anisotropic magnetoresistance and magnetothermopower of cubic ferromagnets U_3As_4 and U_3P_4 was examined on bulk single-crystal samples, in the range from 4.2 K to Curie points 198 and 138 K, respectively. The anisotropic magnetoresistance exceeding 50% was observed, which is about twice as big as that of Permalloys. Moreover, it changes its magnitude and sign with temperature. Such an unusual magnetoresistance is accompanied by anisotropic magnetothermopower also strongly varying with temperature. Applicability of a two-current model to explain the observed phenomena is discussed, and a complementary mechanism of anisotropy induced by trigonal distortion of crystal lattice is proposed.