Speaker
Description
Magnetic two-dimensional (2D) materials are at the forefront of research in recent years, owing to their rich yet tunable properties, conveniently integrable in spintronic, magneto-electric and multiferroic functional heterostructures and prospective devices. The exploration and manipulation of those properties requires understanding of the microscopic origin of magnetic exchange, which is a pertinent challenge beyond the existing theories.
Magnetic 2D materials are typically based on the magnetic exchange between transition-metal (TM) atoms, fostered by the ligand atoms (X). Existing literature offers description of magnetic exchange on atomic level, with occasional attempts to quantify different orbital contributions to the total magnetic exchange between two TM atoms. Moreover, it is known that magnetic exchange between two $d$ orbitals on two TM atoms is in general mediated by $p$ orbital(s) of the X atom(s). However, the exact underlying microscopic mechanisms and the strength of their influence on the magnetic exchange between two $d$ orbitals remain beyond reach.
This motivated us to go beyond, and develop a systematic method to quantify all possible mechanisms that contribute to magnetic exchange for an arbitrary pair of atoms in a given material. The foundation of the method lies in the decomposition of the Green's function into different terms, which are explicitly dependent on the matrix elements of first-principles Hamiltonian in a localized basis.
We applied it to the archetypal magnetic 2D monolayers, CrI$_{3}$ and NiI$_{2}$, to (1) confirm some of the earlier proposed contributions to the atomic exchange, (2) to reveal previously underrated ones, and (3) to exactly quantify microscopic mechanisms behind both. The work is currently being under revision for publication in Physical Review Letters, and non-peer-reviewed version is available online (see Ref. [1]).
Acknowledgements
This work was supported by the Research Foundation-Flanders (FWO-Vlaanderen). The computational resources and services for this work were provided by the VSC (Flemish Supercomputer Center), funded by the FWO and the Flemish Government - department EWI.
References
[1] D. Šabani et al., Beyond the orbitally-resolved magnetic exchange in CrI$_{3}$ and NiI$_{2}$, https://arxiv.org/abs/2502.08273, (2025).
