Magnetic force microscopy (MFM) was used to investigate the magnetic structure of Co75Si10B15. Rapidly solidified strip was produced by planar flow casting, with subsequent annealing to form ε-Co particles in an amorphous matrix. Investigation of the stray field above the specimen indicated that two interacting domain structures were present, one associated with the magnetically soft amorphous matrix and the other associated with magnetically hard ε-Co single domain particles. Tapping mode combined with phase contrast imaging indicated that particle domain orientations depended on the shape and/or magnetocrystalline anisotropy of the particular particle. The MFM observations confirmed the results of previous studies, in that the asymmetric shift in the hysteresis loops observed in partially crystallised CoSiB alloys, manifest as a displacement of the coercivities towards the direction of the initial magnetisation, originates from the presence of ε-Co preciptiated within the bulk. © 1997 Elsevier Science S.A.