Berlin 2018 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 13: Topical session (Symposium EPS and MM, joint session with MA): Magnetism in Materials Science: Thermodynamics, Kinetics and Defects (joint session MM/MA)

MM 13.5: Topical Talk

Montag, 12. März 2018, 17:30–18:00, TC 010

Improving the finite-temperature description of magnetic materials — •Anders Bergman — Department of Physics and Astronomy, Uppsala University,Uppsala, Sweden

State-of-the-art simulations based on electronic structure theory and atomistic models have now evolved to a point where computer-guided materials design has become a realistic option for many classes of materials. In this talk we will introduce improvements to the standard description of finite-temperature magnetism with the aim of increasing the predictive capability of these simulations further.

We present an extended atomistic spin model obtained by augmenting the Heisenberg Hamiltonian to take longitudinal fluctuations of the magnetic moments into account. This is done by parametrisation from a first-principles basis, interpolating from low-temperature ferromagnetic and high-temperature paramagnetic reference states. The method gives a good agreement of Curie temperatures and paramagnetic properties compared with experiments as well as similar, earlier theoretical models.

Introducing quantum statistics into atomistic simulations has been shown to improve the observed temperature dependence of the magnetisation and of the magnetic specific heat. This allows for a more realistic modelling of the magnetic contribution to the free energy and thus a better description of phase-stabilities and related properties. We present how the quantum statistics can be modelled with varying levels on complexity and demonstrate the method for both elemental systems and magnetic alloys.