MODELING THE PERTURBATIVE EFFECT OF MFM TIPS ON SOFT-MAGNETIC THIN-FILMS

The significant current interest in magnetic force microscopy has rais ed a question on the use of such instruments to image magnetically sof t materials, The magnetically hard MFM tip may alter the magnetisation distribution in soft samples such as permalloy. Previous work has sho wn that this problem can be alleviated by using a thin film coated tip with reduced magnetic volume. This work uses a micromagnetic model to examine quantitatively the perturbative effect of an MFM tip on a sof t sample. It is shown that MFM tips can in some cases lead to signific ant changes in the sample magnetisation distribution of up to 60% of s aturation in the worst case, and typically 10-30%. Importantly, small perturbations in the magnetisation distribution are possible without o bvious effects on the MFM image contrast, but which may affect the abi lity to produce quantitative measurements.