Spin-polarized electron momentum density distributions in the Invar system Fe 3 Pt

The one-dimensional projections of the spin polarized electron momentum distributions of ${\mathrm{Fe}}_{3}\mathrm{Pt}$ have been measured, using the magnetic Compton scattering technique, in the temperature range 15--500 K, for the 110 and 111 crystallographic directions in the chemically ordered and disordered phases. The experimental data have been compared with results from electronic structure calculations performed using the linearized muffin-tin-orbital and full potential linearized augmented plane-wave methods and the single-site Green's-function Korringa-Kohn-Rostoker method for the ordered and disordered samples, respectively. The projection of the spin moment momentum distribution as a function of temperature remains characteristic of a Fe $3d$ moment until well above ${T}_{c}.$ No evidence of an indicative change in profile shape is observed that would suggest a redistribution of charge from ${e}_{g}$ to ${t}_{2g}$ orbitals in the Fe band structure that would, in turn, support the Weiss two-state model for the Invar effect.