MAGNETIC AND STRUCTURAL-PROPERTIES OF ERFE3HX HYDRIDES

Pressure-composition isotherms at 20°C for hydrogen absorption in ErFe3 show a well-defined phase at a hydrogen concentration n H∼1.45 with equilibrium pressure∼4 torr, and a second phase with nH≈2.7 having a critical temperature less than 20°C. For larger nH, the sloping isotherms indicate other phases with very low critical temperatures. X-ray studies show that the PuNi3 structure is retained, with increases in lattice constants as hydrogen is added. 166Er Mössbauer spectra show two crystallographically inequivalent Er sites. The corresponding magnetic hyperfine fluids decrease sharply with nH changing at different rates for the two sites. 57Fe Mössbauer spectra show complex patterns arising from the five magnetically inequivalent Fe sites.