Variations of magnetic properties of UH3 with modified structure and composition

Abstract

UH3 based hydrides with modified structure and composition can be prepared using high H2 pressures from precursors in the form of rapidly cooled uranium alloys. While the alloys with a-U structure lead to the b-UH3 type of hydrides, g-U alloys (bcc) lead either to a-UH3 hydride type or nanocrystalline b-UH3. The nanocrystalline b-UH3 structure, appearing for Mo alloying, can accommodate in addition numerous other d-metal components, as Ti, Zr, Fe, Nb. The pure Mo alloyed hydrides (UH3)1 xMox exhibit increasing Curie temperature TC with maximum exceeding 200 K for x ¼ 0.12e0.15. Other components added reduce the TC increment with respect to pure UH3 (170 K). Also alloying by Zr gives a weaker enhancement. Seen globally, the TC variations are rather modest, which reflects the prominence of interaction of U with H. It is suggested that important ingredient is a charge transfer, depopulating the U- 6d and 7s states, while the 5f band stays at the Fermi level.