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Thesis
Home   /   Thesis   /   Theoretical investigation of unconventional spin dynamics

Theoretical investigation of unconventional spin dynamics

Abstract

Theoretical understanding and modelling of spin dynamics is a long-standing problem in magnetism with direct relevance to a wide range of fundamental studies performed on neutron and synchrotron facilities as well as to spintronics applications. This PhD project will be devoted to combined analytical and numerical investigations of selected topical problems in the field of spin dynamics. An ongoing interest in magnetic materials with strong spin-orbital coupling lead to a recent discovery of a new type of excitations: longitudinal magnons, which can be viewed multi-magnon bound states induced by the easy-axis single-ion anisotropy. The first goal in this PhD project will be development of analytical theory for such quantum excitations, their dispersion, and signatures in the neutron scattering and the ESR experiments. The second goal of this project is a combined analytical and numerical investigation of magnon dynamics in frustrated magnets in the presence of structural disorder. This study will, in particular, address the problem of competing ground-state selection mechanisms due to quantum fluctuations and local spin readjustments created by structural disorder. Finally the third part of the Thesis work will focus on simulations of the dynamical properties of magnetic systems at finite temperatures. The spin-precession equations will be solved numerically for finite clusters and combined with the thermal Monte Carlo calculations. This will allow us to study dynamic properties at arbitrary temperatures above and below possible magnetic transitions. A specific physical problem to be addressed with this technique is the presence of the high-energy “ghost” magnon modes above the transition temperature in quasi one- and two-dimensional antiferromagnetic systems. We also plan to study thermal effects on the dynamics of topological excitations (vortices, skyrmions, etc.) from the fully microscopic prospective. The dynamic critical behavior and the diffuse spin dynamics in the paramagnetic state also present interesting and challenging problems.

Laboratory

Institut de Recherche Interdisciplinaire de Grenoble
DEPHY
Université Grenoble Alpes
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