We report measurements of the frequency and temperature dependence of ferro-magnetic resonance (FMR) for a 15-nm-thick yttrium iron garnet (YIG) film grown by off-axis sputtering. Although the FMR linewidth is narrow at room temperature (corresponding to a damping coefficient α = (9.0 ± 0.2) ×10 −4), comparable to previous results for high-quality YIG films of similar thickness, the linewidth increases strongly at low temperatures, by a factor of almost 30. This increase cannot be explained as due to two-magnon scattering from defects at the sample interfaces. We argue that the increased low-temperature linewidth is due to impurity relaxation mechanisms that have been investigated previously in bulk YIG samples. We suggest that the low-temperature linewidth is a useful figure of merit to guide the optimization of thin-film growth protocols because it is a particularly sensitive indicator of impurities.

We report on epitaxial thin films of spinel ferrite Ni0.65Zn0.35Fe1.2Al0.8O4 with strain-induced perpendicular magnetic anisotropy (PMA) and low magnetic damping. Static magnetometry and broadband ferromagnetic resonance experiments show a distinct change in the preferred direction of magnetization from in-plane to out-of-plane when the coherent strain in films changes from ∼2% compressive on (001) MgAl2O4 to ∼0.5% tensile on (001) MgGa2O4 substrates. Significant deviations from the spin-only value (2.0) of the g-factor suggest spin-orbit effects and further support our conclusion of strain-driven magnetic anisotropy in these films. The low Gilbert damping parameter of α = 5 × 10−3 in these ferrite films, combined with their PMA, makes them promising for spintronic and frequency-agile microwave device applications.

We experimentally investigate spin-orbit torque and spin pumping in Y 3 Fe 5 O 12 (YIG)/Pt bilayers with ultrathin insertion layers at the interface. An insertion layer of Cu suppresses both spin-orbit torque and spin pumping, whereas an insertion layer of Ni 80 Fe 20 (permalloy, Py) enhances them, in a quantitatively consistent manner with the reciprocity of the two spin transmission processes. However, we observe a large enhancement of Gilbert damping with the insertion of Py that cannot be accounted for solely by spin pumping, suggesting significant spin-memory loss due to the interfacial magnetic layer. Our findings indicate that the magnetization at the YIG-metal interface strongly influences the transmission and depolarization of pure spin current.

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