Magnetic structure in manganites as probed by magnetic force microscopy

This dissertation describes the use of magnetic force microscopy to directly measure the magnetic structure of a sample on a microscopic level. Our magnetic force microscope has been operated at temperatures ranging from 293 to 4.3 K and fields ranging from 0 to 3 T, providing a method for imaging temperature and field–dependent magnetic phase transitions and domain structures on a local scale. On the instrumentation side, I present details of the design, construction, and operation of a magnetic force microscope with coarse three dimensional tip/sample positioning. On the sample side, I focus primarily on the results of our studies concerning magnetic phase transitions in the manganite La1−x−yPryCaxMnO3, which for some dopings is a colossal magnetoresistive material. I will briefly discuss two ongoing projects: the use of our magnetic force microscope to image field–dependent domain structure in patterned magnetic manganite films and its use as an electrostatic force microscope.