Hysteresis measurement and calculation of magneto-optical sensors based on orthoferrites

The hysteresis behavior and the calculation of the magnetization curves of an orthoferrite plate were investigated to provide a better understanding of the underlying physics of a new passive and wireless magneto-optical rotational velocity sensor based on orthoferrite crystals. The specific behavior is caused by the large domain size and the high velocity of domain wall (DW) motion in the orthoferrite crystal. Calculation by means of the so-called energetic model - supposing statistical domain behavior - yielded results with satisfying correlation between the calculations and measured hysteresis characteristics. Only within the field range of H_m = ±4 kA/m did it turn out to be an improvement to calculate the hysteresis jumps of single domains which are then combined to approach the characteristics of the orthoferrite plate, which has rather big domains of about 0.5 mm width.