Optical microscopy of magnetic phenomena beyond the diffraction limit

Abstract

This thesis explores optical methods to study magnetization dynamics, emphasizing approaches that surpass the optical diffraction limit. Part I reports the discovery of a six-octave magnonic frequency comb in a NiFe thin film driven by MHz radio waves. Material properties and dynamics were probed using NV-center magnetometry and SNS-MOKE microscopy. Micromagnetic simulations support a model based on synchronized switching in distinct film regions. Their distribution is set by the low-field concertina magnetization pattern, which provides local symmetry breaking enabling the process. Part II presents a novel measurement approach combining Brillouin light scattering with SNOM for sub-100 nm spatial resolution. The system integrates a stabilized narrow-band light source and a custom high-throughput, high-resolution spectrometer. Validation on polymer samples demonstrates spectrometer performance and SNOM integration, enabling future nanoscale imaging of large-wave-vector spin waves.