Local Measurement Of Interfacial Interactions Using Ferromagnetic Resonance Force Microscopy

Multilayer structures incorporating nonmagnetic and ferromagnetic materials play an essential role in spintronic devices. Manipulation of the magnetization orientation in ferromagnets using adjacent nonmagnetic materials enables phenomena such as spin-torque driven magnetization switching and auto-oscillation. In order to improve the performance of spintronic devices, understanding of interfacial spin interactions is critical. Here we demonstrate detailed spatially resolved spectroscopic measurements obtained using ferromagnetic resonance force microscopy that provide a route to detailed understanding of spin interactions at normal-metal/ferromagnet interfaces. Our study reveals an unexpected 32-G uniaxial anisotropy field generated in a 20-nm-thick Y3Fe5O12 thin film as a consequence of such an interaction with a 5-nm Au overlayer. The use of the low-damping ferrimagnetic insulator Y3Fe5O12 enables imaging with multiple localized standing spin-wave modes (multimode imaging) confined by the micromagnetic tip. Multimode imaging not only improves the spatial resolution to be as fine as similar to 100 nm, but also potentially enables the contributions of distinct spin interactions to be disentangled. We further discuss in detail the evolution of the multiple localized modes as the probe scans across the internal field step at the edge of the Au film. These capabilities provide the foundation for high spectral and spatial resolution study of spin interactions at the interface between a ferromagnet and a small-volume non-magnetic material including atomically thin two-dimensional materials.