Spin Dynamics Measurements in Micron‐Sized van‐der‐Waals Antiferromagnets

Traditional magnetization dynamics measurements in van der Waals antiferromagnets rely on millimeter‐sized crystals to achieve detectable signal levels. However, conventional approaches become inadequate when investigating micrometer‐scale few‐layer samples, which host unique layer‐dependent phenomena including tunable magnon–magnon interactions and thickness‐controlled mode hybridization. Here, we develop a method enabling ferromagnetic resonance (FMR) measurements on micrometer‐sized antiferromagnetic samples (CrCl 3 ) using a conventional vector network analyzer (VNA)‐based FMR setup. Our approach combines a protective polycarbonate (PC) coating to prevent delamination, mechanical damage, and aging‐induced degradation, with a precision alignment technique that guarantees stable signal acquisition through optimal positioning relative to the excitation source. FMR measurements reveal robust spin dynamics in PC‐protected CrCl 3 , with clearly resolved acoustic and Kittel modes, showing a reduced interlayer exchange field compared to bulk crystals. Remarkably, the magnetic properties remained unchanged after 3 months under ambient conditions, confirming the effectiveness of the PC coating. Thus, our method enables reliable FMR studies of micrometer‐scale van der Waals magnets, bridging the gap between bulk and few‐layer investigations and paving the way for exploring layer‐dependent spin phenomena.