Optical observations of antiferromagnetic S domains in NiO (111) platelets

Some aspects of the dynamical behaviour of S walls are studied at room temperature through in situ optical observations performed on vapour-grown NiO (111) platelets in a magnetic field. The field is applied in the plane of the platelets, i.e., in the easy plane of magnetisation, by changing its strength and/or direction. The observations give direct confirmation of the occurrence of spin flopping for a field above about 15.4 kOe; hence the anisotropy energy associated with the easy axes of magnetisation within the easy plane is estimated as 42 erg g -1 . The observations also give information concerning the field strength necessary for creating S walls in single S domain platelets, and for displacing S walls in multiple S domain platelets. This information is used to evaluate the formation energy and coercivity of S walls.