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

Domain wall networks and their motions and transformations in response to changing magnetic fields ( less than equivalent to 30 Hz) are studied in small, rectangular, easy-axis and hard-axis strips of permalloy film (375 angstrom). 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 study reports optical detection of transformation between domain configurations such as the Landau-Lifschitz structure (LL), LL 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.