Antiferromagnetic domain wall motion in KNiF3 and KCoF3 observed by X-ray synchrotron topography

Domain wall movement has been studied directly in the cubic antiferromagnets KNiF3 and KCoF3. Using synchrotron radiation from the 5 GeV electron synchrotron NINA, X-ray topographs were recorded in fields up to 1–5 T and at temperatures down to 4–2 K. Walls move so as to align spins perpendicular to the applied field and wall motion is reversible over a considerable distance. Quantitative agreement has been found with theoretical predictions using the model of Néel (1954) incorporating a restoring force proportional to wall displacement. The origin of this restoring force is discussed.