Pulse-response properties of rectangular-loop ferrites

An analysis of the voltage pulses obtained across a secondary winding of a ferrite core on reversing the magnetization shows that in the reversal two stages should be distinguished, namely a fast response, related to a magnetization by rotations, and a slower response due to the displacements of domain walls. The viscous movement of the domain walls determines the switching time of the core. It appears that the switching times of rectangular-loop ferrites with widely varying chemical compositions are always of the order of magnitude of one microsecond when the coercive force is of the order of magnitude of one oersted. Higher values of the coercive force mostly go hand in hand with an increased switching time. In order to obtain some information about the origin of the damping of domain-wall displacements, switching times have been measured as a function of temperature and as a function of a uniaxial pressure applied to the core. In the temperature range ¿115 to +250°C the switching time of an arbitrarily chosen rectangular-loop ferrite did not decrease more than by a factor of about three. A uniaxial pressure applied to a ferrite also increases both its coercive force and its switching time. It appears that the switching time is greater when the anisotropies in the ferrite are greater. This can at least partly be explained by the increased distance between the walls in the case of higher magnetic anisotropies. An earlier paper on this subject has been given elsewhere.