Investigating magnetism in oxide heterostructures

NAISS 2024/6-106


NAISS Medium Storage

Principal Investigator:

Igor Dimarco


Uppsala universitet

Start Date:


End Date:


Primary Classification:

10304: Condensed Matter Physics



In this project, we plan to use density functional theory (DFT) and its combination with dynamical mean field theory (DMFT) to pursue the investigation of magnetism in oxide heterostructures of various compositions. We identify two different sub-projects that will be conducted, in connection to the Compute Project NAISS 2023/5-540. In a recent project [Comp. Mater. 8, 1 (2022)], we demonstrated that (111)-oriented superlattices of LaMnO3 and SrMnO3 exhibit a peculiar ferromagnetism, not driven by interfacial phenomena. Varying thickness was found to induce a phase with an emergent separation between Jahn-Teller and breathing distortions [Phys. Rev. B 109, 045435 (2024)]. Next, we intend to analyse magnetism more in detail, by mapping the electronic structure problem onto an effective Heisenberg model, to be solved via atomistic spin-dynamics simulations. This analysis would offer a more direct connection to the experiment, which is important for understanding the applicability of these superlattices in technology as well as for connecting to experimental characterization. Experimental support will be provided by Prof. V. Lazarov and his group, at the University of York. Further work on oxides will be focused on EuTiO3, in various phases. After having investigated the electronic and magnetic properties of the bulk at equilibrium, we now intend to analyse the response to applied strain. Our aim is to identify the competing exchange mechanisms and to understand how their balance may be altered via external stimuli. This insight will be useful to investigate the LaAlO3|EuTiO3|SrTiO3 heterostructure, which has been suggested to host a magnetic quasi two-dimensional electron gas (q2DEG) [Quantum Mater. 7, 1 (2022)]. By combining electronic structure calculations with atomistic spin-dynamics simulations, we intend to clarify the origin of the long range order, the relation between ordering temperature and EuTiO3 thickness, and the role played by the Ti-3d states. The calculation of the X-ray absorption spectra and their comparison with available experimental data will be useful to understand how the nominal valence of Eu (in different ionization states) affects the q2DEG, emphasizing the role played by vacancies and impurities.