Magneto-optic observation of domain motions and instabilities in small permalloy elements

Domain wall networks, their motions and transformations are studied in response to changing magnetic fields (≤ 30 Hz) in small, rectangular, easy-axis and hard-axis stripes of Permalloy film (375Å). Many of the effects reported previously using Bitter solution or Lorentz techniques are now seen optically in real time with a wide-field, high resolution, polarized, laser magneto-optic microscope system. This initial study reports optical detection of transformations between domain configurations such as the Landau-Lifshitz structure (L.L.), L.L. plus diamond, concertina, and bellows. Wall cluster and subcluster artifacts are visible and may be seen to generate (annihilate) or bifurcate (amalgamate) during network motion.