Magnetic domain studies of permalloy wire-based structures with junctions

Permalloy (Ni-80 Fe-20) wire-based structures (30 nm thick and 1 . w . 10 m um wide) with junctions (crosses, networks, H-shapes, rectangular chains an d ring chains) prepared on a GaAs (100) substrate were observed in both the ir demagnetized and remanent states by magnetic force microscopy (MFM) in o rder to investigate the role of junction geometry in domain formation, Exce pt in ring chains, two classes of domain configuration are found at the jun ction: (i) a domain wall-like feature due to abrupt spin rotation and (ii) a triangle-shape domain consistent with a flux closure configuration, Ring chains, on the other hand, form vortex domains at every other junction. The MFM observations are compared with micromagnetic calculations which qualit atively support the magnetic domain configurations.