ES22-Saritas

Author: Saritas, Kayahan - Yale University

Title: Magnetic anisotropy densities through second order perturbation theory for 2D magnets

Abstract: Piezoelectric ferromagnets (PFM) are characterized by having a piezo-active crystalline symmetry and possessing ferromagnetic ordering. Piezoelectrics change their lattice structure when exposed to electric fields which can lead to a change in the magnetic interactions (e.g., ferromagnetic critical temperature Tc). Our first-principles calculations with a data-mining approach reveal that 2H-FeCl2 is the only two-dimensional (2D) monolayered PFM with Tc near room temperature at 260K. The Mermin-Wagner theorem asserts that one must have easy-axis (Ising-like or out-of-plane) magnetic anisotropy for long-range ferromagnetic order to exist in 2D materials. We explain the origin of easy-axis magnetic anisotropy in FeCl2 by developing a new method based on magnetic anisotropy densities as a function of electronic band energies. Our method also explains the origin of easy-plane and easy-axis anisotropies in VSe2 and CrI3 respectively. We show and explain why the magnetic anisotropy of FeCl2 can be enhanced up to 6-folds with modest hole doping. Our results offer design principles to aid the search for new 2D PFM or magnets for novel applications.

Other authors: Ismail-Beigi, Sohrab