Magnetic properties of a single micrometer-sized YIG/FGT multilayer heterostructure revealed by ferromagnetic resonance*

Multilayer heterostructures consisting of a magnetic insulator and 2D spin system offer a promising platform for next-generation spintronic applications. Understanding interfacial spin coupling and transport in such heterostructures require a local microwave spectroscopy technique since the flakes of 2D materials obtained by exfoliation are limited to micrometers in size. Here, we fabricate disks of 20um diameter from epitaxial ferrimagnetic insulator, yttrium iron garnet (YIG), thin-film using pulsed laser deposition, e-beam lithography, and lift-off. We place few-nm thick flakes of van-der-Waals material Fe3GeTe2 (FGT) on the pre-patterned YIG disks and transfer a single disk onto a planar microwave resonator. Using angle-dependent ferromagnetic resonance, we find low-energy spin-wave modes in YIG at several microwave frequencies, allowing for the evaluation of magnetic anisotropy and damping. Using cryogenic measurements, we observe an anomalous temperature dependence of effective magnetic anisotropy. The results shed light on spin phenomena at YIG/FGT interfaces and present an experimental approach for studies of micro-scale magnetic insulator/2D heterostructures.