MAGNETIC AND MOSSBAUER-EFFECT STUDIES OF U6FE HYDRIDE

The dc magnetization, ac susceptibility, heat capacity, and Mossbauer effect for U6FeH17 and beta-UH3 have been examined as a function of te mperature (4.2-300 K) and magnetic field up to 140 kOe. The U6FeH17 cr ystallizes in the Pm3n space group where the metal arrangement is like that of beta-W. The compound turned out to be a ferromagnet with a tr ansition temperature of 173 K differing only slightly from that of bet a-UH3. The saturation magnetization of U6FeH17 at 140 kOe and at 4.2 K is smaller than that for beta-UH3. The temperature dependence of the ac susceptibility showed a sharp maximum of the chi' and chi'' at the para-ferromagnetic transition temperature for both investigated hydrid es. In the U6FeH17 hydride another steplike anomaly at about 140 K has been observed. This anomaly has been confirmed by heat capacity measu rements. No such anomaly in beta-UH3 hydride has been reported for bot h mentioned above types of experiment. The valence-charge-density dist ribution and the main components of the electric field gradient tenser were calculated using the modified Thomas-Fermi approach. Mossbauer s pectra analysis has shown that the iron atoms preferably occupy (6c) s ites in the U6FeH17 lattice. It has been concluded that the [110] axis could be an easy magnetization direction in U6FeH17 hydride.