Structural, magnetic, and defect properties of Co-Pt-type magnetic-storage alloys: Density-functional theory study of thermal processing effects

Using an optimized-basis Korringa-Kohn-Rostoker-coherent-potential approximation method, we calculate formation enthalpies Delta E-f, structural, and magnetic properties of paramagnetic (PM) and ferromagnetic, disordered A1 and ordered L1(0) CoPt, FePd, and FePt systems that are of interest for high-density magnetic-recording media. To address processing effects, we focus on the point defects that dictate thermal properties and planar defects (e.g., c domain and antiphase boundaries) which can serve as pinning centers for magnetic domains and affect storage properties. We determine bulk Curie (T-c) and order-disorder (To-d) transition temperatures within 4% of observed values, and estimates for nanoparticles. Planar-defect energies gamma(hkl)(x) show that the favorable [hkl] defects depend on processing conditions as T-c < To-d in these alloys, and the PM defects agree with those observed. We correlate all properties with the electronic structure.