# Dresden 2017 – wissenschaftliches Programm

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# MA: Fachverband Magnetismus

## MA 38: Electron Theory of Magnetism and Correlations

### MA 38.8: Vortrag

### Mittwoch, 22. März 2017, 11:30–11:45, HSZ 403

**Ab-initio modelling of spin-fluctuations in classical regime for itinerant ferro- and antiferromagnetics.** — •Sergii Khmelevskyi — CMS, IAP, Vienna University of Technology, Vienna, Austria

We present an ab-initio scheme of calculating high-temperature magnetic properties of the itinerant electron systems with strong thermally induced longitudinal fluctuations of the magnetic moments. The scheme is based on the disordered local moment formalism and magnetic force theorem for the calculation of the inter-atomic magnetic exchange interactions. The single-site theory and constrained first-principle calculations has been used for setting the parameters of the mean-field like Heisenberg Hamiltonian with varying amplitude of the spin moment. The transverse (spin-rotation) degrees of freedom, however, have been treated beyond mean-field (Monte-Carlo simulations). We discuss a problem of choosing of a proper statistical measure for the integration over the spin degrees of freedom in classical configurational space. We compare different approaches to the problem for various systems: bcc Fe, fcc Ni, fcc Co, novel itinerant high temperature antiferromagnetic V3Al [1] and "nearly ferromagnetic" FeSi semiconductor. The comparison is done by calculating the magnetic ordering temperatures and high temperature behavior of the susceptibility entirely from first principles. [1] S. Khmelevskyi, Phys. Rev. B 94, 024420 (2016).