MAGNETIC-PROPERTIES OF NICKEL HYDRIDE - A COMPARISON OF MAGNETIC-SUSCEPTIBILITY WITH BAND-STRUCTURE CALCULATIONS

We have measured the magnetic susceptibility of nickel hydride, with an atomic-hydrogen-to-nickel ratio H:Ni almost-equal-to 1:1, in the temperature range 1.4-100 K. The data imply that the magnetic properties originate from three different sources: the non-ferromagnetic beta-phase of nickel hydride with a temperature-independent susceptibility chi(m) = 1.3 X 10(-6) e.m.u. g-1; small precipitates of the ferromagnetic alpha-phase, corresponding to less than 10(-3) of the nickel content in a sample; and small clusters of Ni atoms, which develop a localized moment in an environment with unoccupied hydrogen sites. From the value of chi(m) we calculated a density of states N(E(F)) = 1.09 states per electronvolt per Ni atom. It is concluded, from a comparison with band structure calculations, that the paramagnetic susceptibility of the beta-phase can be described as an enhanced Pauli susceptibility. A partial rearrangement of hydrogen leading to an increased magnetization was observed in the range 180-220 K, and above 270 K the samples rapidly deteriorated.