A theoretical analysis of the frequency dependence of domain wall spacing in a ferromagnetic sheet

The optimum domain size in a demagnetized crystal will be that which results in a minimum value for the sum of the free energies associated with the surface structures and the walls separating the main domains. When the crystal is cyclically magnetized, the increase in domain wall area due to wall bowing will lead to a change in the optimum domain size. A theory is developed, based on a flexible wall domain model, which shows that the low frequency dependence of the spacing that has been observed by many workers can be explained qualitatively by including domain wall bowing in a minimum energy criterion.