Unusual magnetization process in haematite investigated by synchrotron radiation diffraction imaging

The magnetization process of a nearly perfect crystal of haematite is investigated through the observation of domain wall evolution in an applied magnetic field, by white-beam X-ray section topography. The sample is a (111) platelet. The walls are nearly parallel to its main surface. Their contrast changes dramatically with increasing field, but their locations are not altered very much during most of this process. These experimental facts are interpreted as corresponding to a magnetization process which occurs mainly by spin rotation within the domains. The very small basal plane anisotropy of haematite and the pinning of the walls by defects results in this unusual magnetization process, which differs from the standard process for ferromagnets.