Surface energies of stoichiometric FePt and CoPt alloys and their implications for nanoparticle morphologies

Abstract

We have calculated surface energies and surface magnetic order of various low-indexed surfaces of monoatomic Fe, Co, and Pt, and binary, ordered FePt, CoPt, and MnPt using density functional theory. Our results for the binary systems indicate that elemental, Pt-covered surfaces are preferred over Fe- and Co-covered and mixed surfaces of the same orientation. The lowest energy orientation for mixed surfaces is the highly coordinated (111) surface. We find Pt-covered (111) surfaces, which can be realized in the L11 structure only, to be lower in energy by about 400 meV/atom compared to the mixed L10 (111) surface. We conclude that this low surface energy stabilizes the L11 structure in small nanoparticles, which is suppressed in bulk alloys, but has been recently synthesized as thin film for CoPt. From the interplay of surface and bulk energies, equilibrium shapes of single-crystalline ordered nanoparticles and crossover sizes between the different orderings can be estimated.

17 pages, 15 figures, revised version accepted for publication at Phys. Rev. B

References in corpus (1)

• Alloy surface segregation in reactive environments: A first-principles atomistic thermodynamics study of Ag3Pd(111) in oxygen atmospheres

Cited by in corpus (6)

• Magnetism: the Driving Force of Order in CoPt. A First-Principles Study
• Size Effect on Order-Disorder Transition Kinetics of FePt Nanoparticles
• Bias sputtering of granular ${\text{L1}}_0$-FePt films with hexagonal boron nitride grain boundaries
• Magnetic anisotropy of L1${}_0$ FeNi (001), (010), and (111) ultrathin films: A first-principles study
• L1${}_0$ FePt thin films with tilted and in-plane magnetic anisotropy: first-principles study
• Giant perpendicular magnetic anisotropy energies in CoPt thin films: Impact of reduced dimensionality and imperfections