Strong electronic correlations and magnetism in systems containing transition metals and lanthanides
Title: Strong electronic correlations and magnetism in systems containing transition metals and lanthanides
DNr: NAISS 2024/5-676
Project Type: NAISS Medium Compute
Principal Investigator: Igor Dimarco <igor.dimarco@physics.uu.se>
Affiliation: Uppsala universitet
Duration: 2025-01-01 – 2026-01-01
Classification: 10304 10407
Homepage: http://fplmto-rspt.org/
Keywords:

Abstract

In this project, we plan to use density functional theory (DFT) and its combination with dynamical mean field theory (DMFT) to pursue two major lines of research. Our first line of research is focused on oxide heterostructures. 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 affect electronic, magnetic and structural properties all together, which can be used to obtain a phase with an emergent separation between Jahn-Teller and breathing distortions [Phys. Rev. B 109, 045435 (2024)]. Next, we intend to analyze 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. In this regard, we established a collaboration with the experimental group of Prof. V. Lazarov, at the University of York, where synthesis will be attempted. 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 and under applied strain, we now intend to focus on 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. Our second line of research is focused on materials with anisotropic magnetic coupling that may exhibit strong electronic correlations. We previously investigated Fe3Sn, which is a ferromagnetic kagome metal with a high Curie temperature and a large magnetic anisotropy energy. Now, we intend to focus on Fe3Sn2, which is a similar system as Fe3Sn but possesses a structural stacking that makes it closer to the two-dimensional kagome limit. Experimental studies have reported on many exotic features, including massive Dirac fermions [Nature 555, 638 (2018)] and a very large anomalous Hall conductivity [Phys. Rev. B 101, 161114R (2020)]. To understand these effects, as well as the recent observation of electron pockets and bands of mysterious origin in laser-based micro-focused angle-resolved photoemission spectroscopy [Nature 627, 67 (2024)], we will perform electronic structure calculations by means of DFT and DFT+DMFT. We will also evaluate magnetic properties and inter-atomic exchange coupling, with and without relativistic effects, to highlight the differences between Fe3Sn2 and Fe3Sn.