Ni-Pt Phase Diagram: Experiment and Theory

The temperature-composition phase diagram of the ${\mathrm{Ni}}_{1-x}{\mathrm{Pt}}_x$ system was determined by x-ray diffraction and in situ high-temperature measurements of electrical resistivity. The Curie temperatures were also determined for both disordered and ordered alloys. Our results provide direct experimental evidence for the interplay between atomic ordering and magnetism. The experimental measurements are satisfactorily reproduced by a Hamiltonian, solved in the tetrahedron approximation of the cluster-variation method, that contains magnetic interactions dependent on chemical and short-range order.