Magnetic domain studies of permalloy wire-based structures with junctions

Permalloy (Ni/sub 80/Fe/sub 20/) wire-based structures (30 nm thick and 1/spl middot/w/spl middot/10 /spl mu/m wide) with junctions (crosses, networks, H-shapes, rectangular chains and ring chains) prepared on a GaAs(100) substrate were observed in both their demagnetized and remanent states by magnetic force microscopy (MFM) in order to investigate the role of junction geometry in domain formation. Except in ring chains, two classes of domain configuration are found at the junction: (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 qualitatively support the magnetic domain configurations.