Building a Magneto-optical Kerr Microscope by Modifying a Polarizing Microscope

The magneto-optical Kerr effect (MOKE) magnetometry method using a laser is an effective characterization tool capable of measuring local magnetic hysteresis loops of magnetic samples in sub-micron size. Originally, we tried to upgrade our current MOKE hysteresis loop measurement set up to a prototype Kerr microscope that can also capture magnetic domain images. However, it turned out that it is difficult to optimize a laser system for both purposes of measuring intensity for a MOKE hysteresis loop and imaging contrasts of magnetic domains. Therefore, we developed a dedicated MOKE microscope by modifying a regular polarizing microscope for the purpose of imaging magnetic domains of patterned magnetic thin film structures, nanometer/sub-micron-size samples. Permalloy (Py) and SmCo nanocaps were fabricated on nano/microsphere templates using a pioneering fabrication method of nanosphere lithography. By using the MOKE method on our samples we observed contrasts that reflected the presence of magnetic domains of the micrometer scale. By measuring both hysteresis loops and magnetic domains we expect to provide an understanding of the magnetic characteristics of three-dimensional magnetic nanostructures such as our nanocap thin films.