ELECTRONIC-STRUCTURE AND THERMODYNAMIC PROPERTIES OF FE-PT ALLOYS

We discuss the magnetic properties of the Pt-Fe alloys using a combined approach of the fixed-spin-moment, self-consistent electronic structure energy calculations for T = 0, and the improved spin- and density fluctuation theory for T > 0. For T = 0, we show the total energy and equations of state as functions of moment and volume. Special attention is paid to the issue of high- to low-moment transition for PtFe3 Invar. Further, we discuss some improvements to the previously formulated spin- and density fluctuation theory. This theory, using the T = 0 total energy surfaces as a starting point, allows for a description of the thermal behavior of the magnetic and elastic properties of a magnetic material. We discuss the temperature dependence of the volume magnetostriction and bulk modulus, and the pressure dependence of the critical temperature for PtFe3. We compare these quantities with the available experimental data.