Dresden 2011 – scientific programme

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MA: Fachverband Magnetismus

MA 9: Magnetic Materials I

MA 9.4: Talk

Monday, March 14, 2011, 15:30–15:45, HSZ 401

Ab initio modeling of Fe-Mn based alloys — •Denis Comtesse, Heike C. Herper, Mario Siewert, Alfred Hucht, and Peter Entel — Faculty of Physics - University of Duisburg-Essen, 47048 Duisburg, Germany

We present ab initio calculations of structural and magnetic properties of iron-manganese alloys over a wide range of compositions using VASP [1]. We add different amounts of carbon and silicon on complete relaxed interstitial and substitutional lattice positions and analyze the changes of the magnetic exchange interactions J_ij. The exchange parameters are used for Monte Carlo simulations of the Heisenberg model to extend the analysis of the magnetic behavior to finite temperatures and to determine the magnetic transition temperatures. In order to examine the influence of disorder we employed the KKR-CPA method [2] and calculated the exchange parameters for various types of disorder. We find a strong dependence of the critical temperature on the disorder and the carbon content. The disorder always tends to reduce the transition temperature. In case of high carbon concentrations, ordered systems show a strong relation between the iron-manganese composition and the transition temperature.

[1] G. Kresse and J. Furthmüller, Phys. Rev B 54, 11169 (1996)

[2] The Munich SPR-KKR package, version 3.6, H. Ebert et al.