NEAR-SURFACE STRUCTURE OF DOMAIN-WALLS IN IRON SINGLE-CRYSTALS IN A MAGNETIC-FIELD

Remagnetization of the near-surface substructure of 180 degree domain walls in filamentous iron single crystals for the first time is studied by observing the shift of the Bloch points. Annihilation of Bloch point pairs in an external magnetic field is observed. An essential increase in the coercitivity of the microstructure elements (domain walls, vertical Bloch lines and Bloch points) is observed with a concurrent decrease of their dimensions. Oscillation of the domain walls results in a decrease of the coercive field of the Bloch points (H(c)(BP)). The spectra of the Bloch point oscillations activated by the domain wall oscillations are obtained at field strengths below H(c)(BP); the Bloch point oscillations are of a relaxation nature. A significant growth of the amplitude of the Bloch point oscillations is observed on superbarrier motion (H > > H(c)(BP)) at frequencies exceeding 100 kHz. This can be ascribed to a decrease of its dynamic coercive field strength.