ICTS

In this talk, we shall describe the electronic structure of the layered ferromagnet CrI3 where strong SOC from the heavy ligand iodine atoms and the graphene like honeycomb network that is formed by the magnetic Cr atoms holds the potential to give rise to topological electronic and magnetic properties. In particular, we shall obtain the microscopic Hamiltonian for CrI3 and clarify the role of ligand induced spin-orbit coupling on the calculated parameters. We shall argue whether the Kitaev term is important in modelling this system and show that high resolution neutron scattering may be suitable to probe the Kitaev exchange at large B.

(Work done in collaboration with Subhadeep Bandyopadhyay, Finn Lasse Buessen, Ritwik Das, Franz G. Utermohlen, Nandini Trivedi and Arun Paramekanti)

[1] Subhadeep Bandyopadhyay Finn Lasse Buessen,2, Ritwik Das, Franz G. Utermohlen, Nandini Trivedi and Arun Paramekanti, and Indra Dasgupta Phys Rev B 105, 184430 (2022)

We use ferromagnetic resonance (FMR) spectroscopy to determine the values of spin interactions for Chromium trihalides (CrX3, X = Cl, Br, I) such as Heisenberg (J), Kitaev (K), and off-diagonal symmetric (Γ) exchange interactions in the Hamiltonian defined by crystal symmetries and investigate their correlations with spin-orbit coupling (SOC) strength of p orbital of ligand atom X. Three CrX3 compounds provide an excellent material platform for exploring and realizing exotic two-dimensional (2D) spin orders since they have the same crystal structure and have the same Hamiltonian, but different p orbital of ligand X provides the different SOC strength. We find that most magnetic interactions and properties, such as K and Γ, their resulting two magnon band gaps, and the magnetocrystalline anisotropy and Curie temperature T_C, exhibit an exclusive correlation with the single-factor SOC strength of the ligand p orbital, in contrast to Cr-Cr bond distance and Cr-X-Cr path angle, which can also significantly affect them. This shows that the SOC of X plays a central role in the 2D magnetism of CrX3, overwhelming the other key crystalline structural factors. We also calculate and predict the spin wave dispersions with our determined spin interaction constants for three CrX3 and compare them.