Thermodynamic calculations of phase equilibria of Co–Cr–Pt ternary system and magnetically induced phase separation in the FCC and HCP phases

Abstract

The calculations of phase equilibria of the Co–Cr–Pt ternary system have been carried out based on the thermodynamic assessments of Co–Cr, Co–Pt and Cr–Pt binary systems by the calculation of phase diagram technique. The Gibbs energies of the liquid, FCC, BCC and HCP solution phases were approximated by a sub-regular solution model, while those of σ and Cr 3Pt phases were approximated by a compound energy model. Almost all the experimental information on each sub-system has been well described by the present set of thermodynamic parameters. A critical calculation of the magnetically induced miscibility gap between the ferromagnetic HCP and the paramagnetic HCP phase has been conducted, where the two-phase separation has been found at the Curie temperature. The Cr content in the ferromagnetic HCP phase increases and the width of the two-phase separation becomes narrower with increasing Pt content. The present calculations would be useful for the design and development of the perpendicular magnetic recording media.