| The micromagnetic structures of various materials have been studied as a function of applied field, applied pressure, and temperature using a Magnetic Force Microscope (MFM). Using a custom-built electromagnet, the magnetic structure of a TbFeCoGd thin film was measured in an applied field. A technique was developed which allowed the bulk magnetic state of certain films with perpendicular anisotropy to be determined from MFM images of microscopic areas. The observations and measurements of this film were compared with previous theoretical and experimental work on films with perpendicular anisotropy. The domain structures of polished and fracture (111) surfaces of Terfenol-D, a technologically significant magnetostrictive material, were also studied. The sample was imaged before, during, and after application of stress in situ. The quiescent magnetic structure as well as stress-induced domain changes were compared to a theory of magnetostrictive materials. Another experiment explored the discovery of a novel mechanism of magnetic reversal in a TbFeCoGd thin film using stress application from the scanning probe tip. The verification of the purely magnetostrictive origin of this effect and a systematic study of the conditions of reversal were performed. A threshhold for reversal as a function of stress was found. A simple model was developed which predicts this threshhold and allows the determination of the magnetostriction constant using the measurement of this threshhold and bulk parameters of the film. The bulk of the thesis describes the development of a MFM capable of operation at cryogenic temperatures. This instrument can operate in an evacuated environment using frequency detection. The apparatus is described in addition to a detailed discussion of the electronic detection mechanisms. Room temperature and 77 K measurements of a computer hard disk test sample were taken as a test of the apparatus. |
