Dresden 2017 – scientific programme
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MA: Fachverband Magnetismus
MA 56: Bulk Materials: Soft and hard permanent magnets
MA 56.2: Talk
Thursday, March 23, 2017, 15:15–15:30, HSZ 403
The influence of the Madelung potential on magnetic properties of disordered FePt — •Saleem Ayaz Khan1, Peter Blaha2, Hubert Ebert3, Jan Minár1,3, and Ondřej Šipr1,4 — 1New Technologies Research Centre University of West Bohemia, Pilsen, Czech Republic — 2Institute of Materials Chemistry, TU Vienna, Austria — 3Universität München, Department Chemie, Germany — 4Institute of Physics ASCR v. v. i., Prague, Czech Republic
When dealing with substitutional alloys, the random occupation of sites has to be approximated. One can use supercells to include many different local configurations. Or one can rely on a mean field method such as the coherent potential approximation (CPA) to model the situation by an auxiliary effective medium. Computationally efficient single site CPA treats the disorder itself very efficiently. However, being a single-site method, it neglects the effect of fluctuations of the local environment. In particular, the Madelung contribution to the alloy potential cannot be included within the standard CPA.
To learn more about the local aspects of magnetism of disordered FePt, we performed a set of ab-initio relativistic full-potential calculations employing both the supercell approach and the CPA. The focus is on the trends of local magnetic moments with the chemical composition of the nearest neighbourhood of individual Fe and Pt atoms. A small but distinct difference between average magnetic moments obtained when using the supercells and when relying on the CPA is identified and linked to the neglect of the Madelung potential in the CPA.