Description
We systematically investigate g-factor anisotropy in two-dimensional van der Waals magnets CrX3 (X = Cl, Br, I) using broadband magnetic resonance for magnetic ordered states below the critical temperature (Tcr) and for paramagnetic states above Tcr, with varied field orientations. Despite sharing the same layered honeycomb lattice, these compounds exhibit contrasting anisotropies: CrCl3 is an easy-plane antiferromagnet, whereas CrBr3 and CrI3 are easy-axis ferromagnets. From temperature-dependent resonance dispersions with fields applied parallel and perpendicular to the c axis, we uncover opposite trends of g-factor anisotropy: gc > gab in CrBr3 and CrI3, but gc < gab in CrCl3. Across the CrX3 family, both the sign and the magnitude of the g shift are found to correlate closely with the effective anisotropy field, suggesting that magnetic anisotropy provides a useful handle for tuning spin dynamics in van der Waals magnets.
