57Fe Moessbauer studies of nickel hydride

Nickel loaded with hydrogen electrolytically or under high pressure was studied by 57Fe Moessbauer spectroscopy on dilute substitutional iron solutes. Experiments in external magnetic fields at 4.2 K show that Fe species in nickel hydride have magnetic moments between about 4.7 and 2.5 μB and saturation hyperfine fields between 24 and 17 T, depending on the number of nearest hydrogen neighbours. By quenching hydride samples from ambient to liquid nitrogen temperature, non-equilibrium hydrogen distributions in the vicinity of the iron can be frozen in. They relax towards equilibrium between 130 and 150 K within hours, permitting information on hydrogen jump rates to be obtained. (orig.)