Transport studies of Kondo behavior,ferromagnetic and antiferromagnetic order in U1−xThxSb

We report electrical resistivity, Hall effect and magnetization measurements in the system U_1?xTh_xSb for magnetic fields up to 100 kOe. In U_0.14Th_0.86Sb a Kondo-like behavior of the resistivity is detected and the interaction J_df between the conduction d electrons and the uranium f electrons is found to be about ?0.2 eV. The dilution of USb by ThSb leads to large modifications of the electrical transport properties, reflecting the change from antiferromagnetism to ferromagnetism and simultaneously a decrease of the ordered magnetic moment per uranium atom occurs. A simple model is presented which accounts for this decrease assuming that all the conduction electrons added by thorium are polarized antiparallel to the remaining uranium f electrons due to the negative J_df. The Kondo temperature is used to estimate the band width and the binding energy of the 5f state.