Dynamic behavior of magnetic bubbles

Detailed stroboscopic observation of magnetic bubbles has been performed on Permalloy overlay circuits, such as T bar and Y bar utilizing YFeO3, TbFeO3, and ErFeO3platelets, and the results have been analyzed on the basis of bubble domain dynamics. A new anomalous bubble propagation mode, recently derived theoretically, has been verified semiquantitatively by experiment. In the anomalous mode, a bubble tends to propagate back and forth along the Permalloy overlay, resulting in a mean forward velocity smaller than the normal velocity determined by the drive frequency. Two different methods, which determine the ratio between the effective bubble driving field intrinsic to an unsaturated Permalloy overlay configuration and the external driving field, have been proposed and the ratios for various configurations have been measured. The typical values are 0.3 for T bar, 0.5 for Y bar, 0.6 for two-sided bars, and nearly 1.0 for two-sided T bars in the orthoferrites with about 10 μm spacing between Permalloy overlays and platelets. The two-sided T bar circuit makes it possible to drive TbFeO3up to 380 kHz.