MAGNETOOPTICAL AND MAGNETIC STUDY OF AMORPHOUS U-AS, U-AS-CU, AND U-AS-TI FILMS

Magneto-optical and magnetic properties are presented in sputtered amorphous thin films of U-As, U-As-Cu, and U-As-Ti. Included are magnetization, Hall effect, resistivity, and polar Kerr-rotation measurements. The U-As films show maximum magnetization and Curie-temperature values at x congruent-to 57 at. % U concentration. The largest Kerr rotation of -2.7-degrees is measured in U61AS39 at 1.1 eV. The Kerr response in the U-As-Cu films is much smaller reaching -1.05-degrees at 1.05 eV in U43As28Cu29. Maximum Kerr rotation in the U-As-Ti films is -1.45-degrees at 1.3 eV in U42As49Ti09. At U concentrations x < 55 at. %, the U-As system shows phase separation into two amorphous phases, presumably a metallic UAs and a semiconducting UAS2 phase. In the U-As-Cu system, for [U]/[As] ratio congruent-to 0.7, magneto-optical evidence for such a phase separation is presented as well. The U-As-Ti films, however, do not show any indication of phase separation in the composition range investigated. It is concluded that the addition of Cu to U-As does not change the local coordination of the U atoms, while the addition of Ti changes the local coordination of the U atoms to a configuration as in U-As with high [U]/[As] ratios. A formula for the influence of the substrate on the Kerr rotation is derived.