Data-Intensive Spatial Mapping of the Longitudinal Spin Seebeck Effect in Normal Metal/Magnetic Insulator Devices*

The rapidly emerging field of spincaloritronics demands new approaches that access the subtle relationship between spins and heat. As a key benchmark, we demonstrate a data-intensive method for spatially mapping the longitudinal spin Seebeck effect (LSSE) in a ferrimagnetic insulator film (YIG) with a thin metal layer (platinum). By spatially scanning a femtosecond pulsed laser (with a large field of view of up to 2mm) over the Pt/YIG device, we use the mobile thermal gradient of the laser pulse to spatially resolve the photovoltage generated by the inverse spin Hall effect. Rotating the applied magnetic field direction over 360 degrees in both in- and out-of-plane directions allows us to remove contributions of the Seebeck effect and measure only the LSSE signal. We find LSSE decay lengths on the order of 100 microns as well as deviations from expected sinusoidal behavior, even at magnetic fields far in excess (0.5 T) of saturation levels. The rich visualization afforded by our technique will have important implications for the next-generation of spincaloritronic devices utilizing magnetic insulators.