Dresden 2020 – scientific programme
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MA: Fachverband Magnetismus
MA 49: Focus Session: Higher-Order Magnetic Interactions – Implications in 2D and 3D Magnetism II
MA 49.1: Invited Talk
Thursday, March 19, 2020, 15:00–15:30, HSZ 04
The role of itinerant electrons and higher order magnetic interactions among fluctuating local moments in producing complex magnetic phase diagrams. — Julie Staunton1, Eduardo Mendive-Tapia1,2, and •Christopher Patrick1,3 — 1University of Warwick, U.K — 2Max-Planck Institut Fur Eisenforschung GmbH, Germany — 3University of Oxford, U.K.
When external stimuli or varying temperature alter its magnetic properties a metal's complex electronic fluid with its emergent magnetic 'local moments' transforms. In this context the ab initio Density Functional Theory-based Disordered Local Moment method can successfully locate and characterise magnetic phase transitions and calculate caloric effects. It will be shown how the theory provides a Gibbs free energy function of local moment order parameters with two central objects - local moment correlation functions in the paramagnetic state and local internal magnetic fields as functions of magnetic order. The potentially most stable magnetic phases and dominant interactions between pairs of local moments are identifiable from the first. Higher order correlations extracted from the second produce effective `multi-site' magnetic interactions depending on how the electronic structure evolves with the state and extent of magnetic order. The approach will be illustrated by applications to the magnetic order of the heavy rare earth metals, the tricritical metamagnetism in frustrated antiferromagnets with rich magnetic-strain phase diagrams and associated caloric effects, and finally the exceptional non-hysteretic first order magnetic phase transition in the divalent lanthanide compound Eu2In.