Ferromagnetic properties at high fields and high pressures of nickel-platinum alloys near the critical concentration for ferromagnetism

The magnetic properties of ferromagnetic Ni-Pt alloys containing 42.9, 45.2, 47.6, and 50.2 at.% Ni were measured in magnetic fields up to 60 kOe, at temperatures between 4 and 60 K, and at pressures up to 7 kbar. The results are presented in terms of Arrott and Mathon plots whose essential straightness over a broad range of alloying contents and external influences provides evidence for the close applicabilities of weak-ferromagnetic theory based on the intinerant-electron model. This model is used to discuss the results quantitatively and the pressure dependence of the critical concentration is estimated, in good agreement with observation. The effective interaction $U$ is found to be 0.44 eV for these alloys, while the ratio of $U$ to the bare interaction is found to be 0.65. The results are compared quantitatively with those for other similar materials, in particular Zr${\mathrm{Zn}}_2$.