Dresden 2009 – scientific programme

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MA: Fachverband Magnetismus

MA 36: Magnetic Particles and Clusters II

MA 36.5: Talk

Thursday, March 26, 2009, 16:15–16:30, HSZ 401

Surface energies of Fe, Co, Mn, Pt and their alloys: An ab initio study — •Antje Dannenberg, Markus Ernst Gruner, and Peter Enetl — Universität Duisburg-Essen, 47048 Duisburg, Germany

L1₀-ordered FePt and CoPt nanoparticles are considered as promising materials for ultra-high density magnetic recording applications. Since the energies of surfaces and internal interfaces play an important role in determining the equilibrium shape of the particles, their analysis is of fundamental interest.

We here show the results of a systematic study of the energies and magnetism of low-indexed surfaces for the monoatomic systems Fe, Co, and Pt, as well as for the binary alloys FePt, CoPt, and MnPt. For L1₀-ordered, stoichiometric alloys we present a method which is based on surface energy phase diagrams in order to evaluate the surface energy contributions of the single material components. For transition metals this has not been done before. We find, that especially platinum covered {111} facets show extraordinary low surface energy while the (001) surface, which is needed for the desired L1₀-cuboctahedron, lays higher in energy. This gives rise to the appearance of multiply twinned icosahedra in gas phase experiments. The energies are calculated within density functional theory using the VASP code and the surfaces were modeled within the slab approach.