Magnetic moment distribution in uranium monosulphide

Abstract

Single crystals of cubic, ferromagnetic uranium monosulphide have been examined by polarized neutron diffraction to yield accurate measurements of the magnetic scattering in forty-three nonequivalent Bragg reflections. Together with magnetization data, these measurements show that the magnetic moment distribution in the crystal is associated primarily with the 5f shell of the uranium ion, and that there is a small negative moment on the 7s or 6d electrons of uranium and negligible moment on the sulphur ion. The observed magnetic scattering has been compared with the value calculated for isolated uranium ions, and for uranium ions in a cubic crystal field, assuming one, two, three of four 5f electrons. The best fit is given by a model for the uranium ion designated 5f2, 3H4, Gamma 1, in which the exchange field is of comparable magnitude to the crystal field giving an ordered magnetic moment of 1.7 mu B per uranium atom.