Rotational hysteresis loss in single-crystal silicon-iron

Measurements have been made, using a torque magnetometer, of the rotational hysteresis loss at various magnetic inductions on 3% (nominal-weight) silicon-iron discs cut from single crystals with the planar orientations (100), (110) and (111). The variation of the hysteresis loss with magnetic induction has been obtained for the three principal crystal directions [100], [110] and [111], from normal B/H loop measurements on single-crystal picture frames. Variations in the magnitude and direction of the field both took place slowly, so that essentially static results were obtained. The manner in which the ratio of the rotational hysteresis loss to the hysteresis loss depends on the magnetic induction B for the three planes and directions is considered in terms of an existing theoretical model of the magnetic-domain changes that take place during the rotational hysteresis and normal hysteresis loss cycles. Photographs of the domain pattern on the planes and the variation of the pattern as the field is rotated are shown; these enable the rotational hysteresis loss to be discussed in terms of the energy required for the creation and annihilation of various domain configurations.