MAGNETIC SWITCHING, RELAXATION, AND DOMAIN-STRUCTURE OF A CO SI(111) FILM/

We have used scanning magneto-optic Kerr effect (MOKE) microscopy to i nvestigate the magnetic relaxation of a polycrystalline hcp 125 angstr om Co/Si(III) film with planar uniaxial anisotropy, on time scales bet ween 10 and 2400 s and with a spatial resolution of 15 mum. In a stati c magnetic field slightly less than the coercive field and applied alo ng the easy axis direction, domains develop and the magnetization reve rsal proceeds via displacements of 180-degrees domain walls. Microscop ic images of this metastable state allow the 180-degrees domains to be identified by calibration of the MOKE signal with respect to that for the saturated magnetization states. The 180-degrees reversed domains are observed to grow in the direction of the field in the form of narr ow fingers, extending via short Barkhausen jumps, randomly spaced in t ime over the entire time-scale range investigated, with typical distan ces between pinning sites of the order of microns. This reversal behav ior is qualitatively similar to that reported for Au/Co perpendicular anisotropy films a few monolayers thick.