SKM 2021 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 14: Focus Session: Higher-Order Magnetic Interactions - Implications in 2D and 3D Magnetism II

MA 14.1: Hauptvortrag

Donnerstag, 30. September 2021, 13:30–14:00, H5

The role of itinerant electrons and higher order magnetic interactions among fluctuating local moments in metallic magnets — •Julie Staunton — University of Warwick, Coventry CV4 7AL, 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. The itinerant electrons, coupled to these more localised spin degrees of freedom, have a profound effect on structure, electronic transport, and so on. The ab initio Density Functional Theory-based Disordered Local Moment method successfully describes this physics. It can locate and characterise magnetic phase transitions and calculate temperature and field-dependent magnetic properties. 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 'exchange' interactions between pairs of local moments or effective 'spins' are identifiable from the first. Higher order magnetic interactions are extracted from the second and depend 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 and its link to the Fermi surfaces of rare earth metals and their compounds, permanent magnetic properties and the rich magnetic-strain phase diagrams and associated caloric effects of some transition metal antiferromagnets.