Magnetostriction, Thermal Expansion, and Specific Heat of a Nearly Ferromagnetic Compound:Ni3Ga

The properties of ${\mathrm{Ni}}_3$Ga show considerable variability depending upon annealing conditions. We measured three samples and for the best (selected by the criteria of field-independent and low susceptibility, temperature-independent susceptibility at low temperature, and quadratic magnetostriction) we obtain from the magnetostriction a value, $\frac{\partial \ln \overline{I}}{\partial \ln V}=1.4\mathrm{}$, for the volume dependence of the product, $\overline{I}=I{N}_0$, of the exchange interaction and the bare density of states. The specific heat, measured in a 100-kOe field to suppress spin-fluctuation and superparamagnetic effects, and the low-temperature susceptibility, give a value $S=30\mathrm{}$ for the exchange-enhancement factor. The thermal expansion has an unusual temperature dependence in zero field and is drastically changed by applying a 90-kOe field. This measurement and the measurement of the specific heat in a large field were unsuccessful in distinguishing spin-fluctuation effects from the superparamagnetic effects which undoubtedly occur even in our best sample of ${\mathrm{Ni}}_3$Ga.