Development of a Near-Field Magneto-Optical Microscopy for Studying Ultrafast Magnetization Dynamics

Apertureless magneto-optical near-field microscopy is developed for studying subpicosecond spindynamics at nanometer spatial scale. Polarization modulation and tip vibrations are implemented. Polarization responsivity of the tip-induced scattering is demonstrated using polarization modulation and tip vibrations. A near-field magneto-optical contrast is achieved for a thin ferromagnetic film with in-plane magnetization; however, its interpretation is shown to be nontrivial. Distribution of the evanescent field is measured vs. tip-sample distance. Interference of the near-field with the far-field scattered light is found at distances ca. 300 nm and more, and strong tip-surface interaction that quenches the detected scattering is found at distances below 20 nm.