Studies of the surface domain structure of cobalt monocrystals by the SEM type-I magnetic contrast and Bitter colloid method

Abstract

The type-I magnetic contrast in a scanning electron microscope (SEM), the conventional Bitter pattern method and the colloid-SEM method have been applied for investigating the magnetization configuration at the (0 0 0 1) surface of thick cobalt monocrystals. All the methods used have been digitally enhanced. In particular, thanks to this, detailed studies by the conventional Bitter technique in zero or weak external magnetic fields, which were not possible before, could be made. The magnetic images observed are analyzed in terms of the domain structure. Type-I magnetic contrast observations show that the surface domain structure of bulk cobalt (at room temperature) is substantially determined by its uniaxial magnetocrystalline anisotropy perpendicular to the (0 0 0 1) surface. From the behavior of the Bitter patterns under the influence of external magnetic field it can be concluded that regions with different in-plane magnetization components are also present on the crystal surface. As a consequence, the magnetization direction at the (0 0 0 1) surface of bulk cobalt monocrystals is generally tilted away from the surface and changes from one domain region to another. Some aspects related to the character of the domain structure observed are discussed in more detail. The results obtained by the methods used are compared with each other as well as with those reported in the literature and obtained with other domain observation methods.