Scanning near-field optical microscope for the imaging of magnetic domains in optically opaque materials

We describe a scanning near-field optical microscope capable of magnetic imaging in optically opaque materials. The near-field probe is a ∼30 nm Ag particle, optically excited near the surface plasmon resonance frequency. The separation of the probe and sample is regulated by a Newton ring interferometer. The polarization rotation of the scattered light due to near-field magneto-optic interactions is measured. A two-dimensional image is presented of thermomagnetically recorded magnetic domains in a perpendicularly magnetized Co/Pt multilayer material with 0.5-μm-diam domains at one micrometer spacing. Images suggest a resolution of <100 nm.