Doctoral Defense in Physics - Kristina Ignatova

Doctoral candidate:
Kristina Ignatova

Title of thesis:
Structural and magnetic properties of V2O3-based magnetic heterostructures

Opponents:
Dr. Arantxa Fraile Rodríguez (Associate Professor in Experimental Condensed Matter Physics in the University of Barcelona, Barcelona) Prof. Dr. Wolfgang Kuch (Professor at Freie Universitat, Department of Physics, Institute of Experimental Physics, Berlin)

Doctoral committee:
Dr. Fridrik Magnus, Research Professor at the Science Institute, University of Iceland.
Dr. Gunnar Karl Pálsson, Senior Lecturer/Associate Professor at Uppsala University

Chair of Ceremony:
Dr. Einar Örn Sveinbjörnsson, Professor and Head of the Faculty of Physical Sciences,University of Iceland

Abstract:
Vanadium sesquioxide, typified by its first-order metal-insulator transition, structural phase transition, and magnetic changes, transition from a high-temperature rhombohedral metallic and paramagnetic state to a low- temperature insulating monoclinic antiferromagnet. The three transitions occur simultaneously, presenting a complex, intertwined phenomenon. Investigating the phase coexistence region in V2O3 is crucial, as its transition is intrinsically inhomogeneous, offering a unique scenario where two phases exist simultaneously within a narrow temperature range. This characteristic, coupled with the ability to manipulate it through various parameters, not only underscores V2O3’s distinctiveness but also amplifies its appeal from an applications standpoint, signaling a rich avenue for further research into this material’s potential. The complex nature of V2O3, characterized by simultaneous transitions, offers a unique opportunity to explore the properties of bilayers and observe how overlying layers are affected by the transitions through the interface. For instance, it allows for the creation of a system with a ferromagnet/paramagnet interface at room temper- ature and a ferromagnet/antiferromagnet interface at low temperatures. Particularly at low temperatures, interfacing a ferromagnetic layer with V2O3 introduces the potential for an exchange bias effect, which arises from the ferromagnetic/antiferromagnetic interface interaction. Exchange bias systems are extensively researched for their capacity to increase ferromagnetic coercivity and stabilize magnetization from thermal fluctuations, thus providing a method to manipulate magnetic properties. V2O3 demonstrates that alterations in crystal structure due to structural phase transitions can be leveraged to influence magnetic characteristics, thereby introducing an extra dimension of control via its magnetic transition phenomena.

About the doctoral candidate:
Kristina began her Ph.D. in physics at the end of 2020 during the COVID-19 pandemic. She completed both her bachelor's and master's degrees in physics at Ural Federal University in Ekaterinburg.