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Table-top Measurement of Local Magnetization Dynamics Using Picosecond Thermal Gradients: Toward Nanoscale Magnetic Imaging

Recent advances in nanoscale magnetism have demonstrated the potential for spin-based technology including magnetic random access memory, nanoscale microwave sources, and ultra-low power signal transfer. Future engineering advances and new scientific discoveries will be enabled by research tools capable of examining local magnetization dynamics at length and time scales fundamental to spatiotemporal variations in magnetic systems - typically 10 - 200 nm and 5 - 50 ps. A key problem is that current table-top magnetic microscopy cannot access both of these scales simultaneously. In this letter, we introduce a spatiotemporal magnetic microscopy that uses magneto-thermoelectric interactions to measure local magnetization via the time-resolved anomalous Nernst effect (TRANE). By generating a short-lived, local thermal gradient, the magnetic moment is transduced into an electrical signal. Experimentally, we show that TRANE microscopy has time resolution below 30 ps and spatial resolution limited by the thermal excitation area. Furthermore, we present numerical simulations to show that the thermal spot size sets the limits of the spatial resolution, even at 50 nm. The thermal effects used for TRANE microscopy have no fundamental limit on their spatial resolution, therefore a future TRANE microscope employing a scanning plasmon antenna could enable measurements of nanoscale magnetic dynamics.