Cobalt--Ferrous ferrite with re-entrant hysteresis loop

If the field Hrrequired to initiate flux reversal exceeds the Hwrequired to continue reversal, a re-entrant hysteresis loop results. This has been observed in magnetically annealed cobalt-ferrous ferrites in which Hrat 10 to 20 Oe may be as high as at room temperature. Frequently, these ferrites are bistable and show no minor loops. Flux reversal appears to involve only one domain wall, giving rise to high squareness but slow switching ; typical values for a 12-mm toroid are and s Oe. Intermediate stabilized magnetization states have been introduced into these materials by a simple annealing procedure. Switching now occurs between three or more magnetization states, providing the basis for a multistable device. Details of preparation and measurement are given and the results discussed in terms of various models.