Magnetic force imaging of domain structures for a (Pr/Nd)FeB alloy

Magnetic force microscopy (MFM) has been used to image the magnetic stray field from a (Pr/Nd)FeB hard magnetic alloy containing alpha-Fe regions. Images were acquired with three different sensing tips (CoCr, NiFe and Fe/SiO2 coated Si). The MFM images were compared to optical Kerr effect images from the same area. Ken images of the (Pr,Nd)(2)Fe14B grains were similar to MFM images obtained using the CoCr tip, revealing a regular open-flux magnetic structure for those grains imaged on a plane perpendicular to the easy direction and stripe domains on those grains imaged on a plane containing the easy direction. MFM images indicated that the alpha-Fe particles were single domain, while Kerr images suggested a substructure within alpha-Fe. The low coercivity NiFe and Fe/SiO2 sensing tips provided images only of the magnetic domain boundaries. The difference in image characteristics between the CoCr and NiFe and Fe/SiO2 tips is believed to be associated with the extent to which the initial tip magnetisation is changed by the stray field from the sample. (C) 1998 American Institute of Physics.