Magnetic imaging in the presence of an external field: erasure process of thin film recording medium

The evolution of microscopic magnetic structures on a thin film recording medium has been imaged by applying a progressively increasing external magnetic field. Images from magnetic force microscopy with an in situ magnetic field revealed features attributable to probe-induced and sample-induced effects. The probe effects result in the preferential sensitivity of the MFM imaging to the component of the local sample field in the direction of the probe's magnetization. The reorientation of the probe's magnetization with respect to the sample plane direction causes the change in instrument response from detecting surface magnetic charges (magnetization divergence sensing) to detecting the surface magnetization distribution. Sample effects are more prominent at higher fields and the micromagnetic features of the recorded patterns follow characteristic sequence as the unfavorably magnetized features of the recorded patterns follow a characteristic sequence as the unfavorably magnetized areas switch in the direction of the external field.