Regensburg 2019 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 55: Electron theory and micromagnetism

MA 55.8: Vortrag

Freitag, 5. April 2019, 11:30–11:45, H38

Critical temperature and effective magnetic moment of experimentally known magnetic Heusler alloys from first principles — •Roman Kováčik¹, Phivos Mavropoulos², and Stefan Blügel¹ — ¹Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany — ²Department of Physics, National and Kapodistrian University of Athens, GR-15784 Zografou, Greece

We present systematic calculations of the critical temperature (Curie or Néel) and the effective magnetic moment of a large number (∼150) of experimentally known magnetic Heusler alloys. The method of calculation comprises three steps: (i) calculation of the ground-state electronic structure within density functional theory (local spin density approximation and generalized gradient approximation) employing the Korringa-Kohn-Rostoker Green function method [1], (ii) extraction of exchange parameters to fit the Heisenberg model [2], and (iii) Monte Carlo simulation based on the Heisenberg model. We analyze the critical temperature dependence on various parameters defining the alloys and address the effect of the longitudinal spin fluctuations on selected alloys. The effective magnetic moment reflecting the degree of short range order above the critical temperature is obtained by fitting the magnetic susceptibility to the Curie-Weiss law and compared to available experimental data. Support from JARA-HPC (jara0182) and the EU CoE MaX (grant no. 676598) is gratefully acknowledged. [1] H. Ebert et al., Rep. Prog. Phys. 74, 096501 (2011), also see: www.judft.de. [2] A. I. Liechtenstein et al., JMMM 67, 65 (1987).