Spin-Heat Coupling and Thermal Spin Transport in Rare-Earth Iron Garnet Heterostructures

Spin-heat coupling and thermal spin transport are topical areas of interest in magnetism. The origin of Spin Seebeck effect (SSE) and its relationship with magnetic anisotropy as well as magnon propagation across magnetic insulator/heavy metal interfaces have remained challenging issues. We have pioneered the technique of RF transverse susceptibility to probe the effective magnetic anisotropy in magnetic materials and heterostructures. Combining these experiments with SSE and anomalous Nernst effect (ANE) measurements, we have shown correlation between bulk and surface anisotropy with the field and temperature dependence of SSE in yttrium iron garnet (YIG)/Pt heterostructures and other compensated ferrimagnets [1,2]. Recently, our group has shown, for the first time, a scaling of longitudinal SSE in gadolinium iron garnet (GdIG) films with different thickness and on different substrates across the compensation temperature [3]. Our ongoing work on thulium iron garnet (TmIG) heterostructures with varying film thickness reveals the clear role of anisotropy and damping on the SSE. From RF susceptibility, SSE and FMR spin pumping experiments, quantitative analysis of the magnon propagation length has been done. Overall, this talk would present new results in the thermal spin transport of garnet heterostructures which are of fundamental importance in spintronics.