MAGNETIC EXCITATION-SPECTRA AND THERMODYNAMICS OF AMORPHOUS PRNI5

Neutron inelastic scattering measurements have been done on amorphous Pr16.7Ni83.3 and crystalline PrNi5 after different steps of heat treat ment of the samples. The magnetization, the heat capacity in magnetic fields up to 80 kOe, and the crystallization of the amorphous samples have also been studied. The magnetic contribution to the neutron inela stic scattering and to the heat capacity has been separated from the c ontributions due to phonons and has been analyzed for the amorphous sa mples. The magnetic excitation spectra of the Pr3+ ground state J mult iplet in the amorphous and the polycrystalline samples show strong qua litative differences: a broad and low energy (similar to 1 meV) peak i n the amorphous samples instead of narrow crystal held excitations in the same samples after crystallization. The magnetization curves of th e amorphous sample proved to be nonlinear at temperatures lower than 2 0 K and evidence for a transition to ferromagnetic correlations in the amorphous samples is given. A nearly stepwise transition from the dis ordered to the ordered crystalline local structure is observed in the neutron scattering experiments done with samples after annealing at di fferent temperatures. The phenomenological model of a deformed crystal has been worked out in order to interpret all experimental data consi stently.