Ferromagnetism with TC=200 K in the amorphous 5f compound UH3Mo0.18

UMo0.18 can absorb hydrogen at elevated H-2 pressures. The product is a compact but brittle hydride UH3Mo0.18, which is to some extent analogous to beta-UH3, but it is almost amorphous (the grain size smaller than 1.2 nm). It is ferromagnetic, and its Curie temperature (200 K) is higher, despite the disorder, than that of beta-UH3 (approximate to 170 K). We also registered an increase in U magnetic moments. The randomness, together with the large anisotropy inherent to U systems, leads to a very high coercivity, reaching 3.7 T at low temperatures. As amorphization normally tends to suppress magnetic ordering of U compounds, the hydride represents a different class of materials, amorphous U-based ferromagnets with relatively very high Curie temperatures.