Observation of magnetic domain patterns in terbium and dysprosium

Magnetic domain patterns on terbium and dysprosium single crystals at liquid helium temperature have been obtained by the method of Hutchinson et al. (1965). On (0001) surfaces, the patterns consisted of markings parallel to (1100) directions. On surfaces parallel to (0001), the patterns consisted of lines and bands both parallel and perpendicular to (0001). The main features of the patterns on terbium could be interpreted on the basis of a structure consisting of thin slab like domains, magnetized in (1100) directions, separated by 180 degrees domain walls lying on (0001) planes, together with surface closure domains. The patterns on dysprosium have similar features to those on terbium but they are difficult to interpret on the assumption that the easy directions of magnetization are (1120).