Dynamical electronic correlations and chiral magnetism in the van der Waals magnet Fe4GeTe2

Among the quasi-two-dimensional van der Waals magnetic systems, Fe4GeTe2 makes a profound impact due to its near-room-temperature ferromagnetic behavior and the complex magnetothermal phase diagram exhibiting multiple phase transformations, as observed from magnetization and magnetotransport measurements. A complete analysis of these phase transformations in light of electronic correlation and its impact on the underlying magnetic interactions remain unexplored in the existing literature. Using first-principles methodologies, incorporating the dynamical nature of electron correlation, we have analyzed the interplay of the direction of magnetization in an easy-plane and easy-axis manner with the underlying crystal symmetry, which reveals the opening of a pseudogap feature beyond the spin-reorientation transition temperature. The impact of dynamical correlation on the calculated magnetic circular dichroism and x-ray absorption spectrum of the L-edge of Fe atoms compare well with existing experimental observations. The calculated intersite Heisenberg exchange interactions display a complicated nature, depending upon the pairwise interactions among the two inequivalent Fe sites, indicating a Ruderman-Kittel-Kasuya-Yosida-like behavior of the magnetic interactions. We note the existence of significant anisotropic and antisymmetric exchange interactions, resulting in a chirality in the magnetic behavior of the system. Subsequent investigation of the dynamical aspects of magnetism in Fe4GeTe2 and the respective magnetothermal phase diagram reveals that the dynamical nature of spins and the decoupling of the magnetic properties for both sites of Fe is crucial to explain all the experimentally observed phase transformations. Published by the American Physical Society 2025