ISBN 9783843948913

978-3-8439-4891-3, Reihe Physik

Korbinian Geirhos
Polar and Magnetoelectric Properties of Lacunar Spinels

149 Seiten, Dissertation Universität Augsburg (2021), Softcover, A5

Zusammenfassung / Abstract

Multiferroic materials exhibit simultaneously a polar and a magnetic order, making them promising candidates for application in future advanced electronics. Lacunar spinels, which recently attracted tremendous interests, are the only class of polar materials exhibiting cluster-Jahn-Teller effect induced polar order. The present thesis is focused on three different aspects of the physical properties of lacunar spinel compounds. As a first aspect, this work shows that depending on the type of symmetry lowering in these materials the polar order can be not only a ferroelectric, but also an antiferroelectric one. As a second aspect, it is demonstrated, that an efficient control of the domain population in the ferroelectric lacunar spinels is possible by electric and magnetic fields. Since the ferroelectric lacunar spinels are at the same time magnetic at low temperatures, rendering these materials multiferroic, their magnetic phase diagrams and the influence of the magnetic anisotropy and strength of the spin-orbit coupling on the stability of the magnetic phases are investigated. As a last aspect, the properties of the ferroelectric domain walls of lacunar spinels are studied. These studies reveal local magnetoelectric magnetic states confined to the ferroelectric domain walls and conducting ferroelectric domain walls, which are highly susceptible to magnetic fields. These results not only explore the new aspects of Lacunar spinels but also help in understanding the physics of magnetoelectric multiferroics.