Ribbons were annealed in the demagnetized state with one wall along the ribbon middle. This wall becomes pinned during the heat treatment. Reentrant reversal occurs when reverse domains are nucleated at the ribbon edge with a threshold field larger than the demagnetizing field; this wall does not annihilate when it meets the pinned wall but leaves a line of reverse domains stabilized by ripple in the anisotropy. These domains permit a regular smooth reversal for the demagnetization process until the ribbon returns to the pinned configuration. The regular loop appears when the ribbon has been completely saturated by a large field. Mobile walls are nucleated on both sides of the pinned wall so that the ribbon does not return to the pinned configuration. Reversal now follows the usual demagnetization curve over the entire cycle. Kerr magnetooptical domain and domain wall observations are used in this investigation. All of the possible wall structures predicted by the model of asymmetric flux closed Bloch walls were identified.
展开▼
