Magnetic structure of vortex and antivortex states in patterned Co elements studied by using scanning ion microscopy with polarization analysis

Abstract

Scanning ion microscopy with polarization analysis (SIMPA) is used to investigate the surface magnetic structure of patterned Co elements created in situ by focused ion-beam lithography from thin (30nm) Co films deposited on Si(100) substrates by electron-beam evaporation. The diameter d of the circular-shaped Co elements is varied between 5 and 38μm. Three-dimensional, spin- and spatially resolved SIMPA spin maps directly reveal the nonuniform micromagnetic structure of magnetic vortex and antivortex states. They are dominated by a circular or hyperbolic surface magnetization profile with a wide vortex or antivortex core in the center with a perpendicular surface magnetization component which decreases with increasing distance from the core. Varying d, the vortex wall thickness can be changed from 0.6 to 4.2μm. For Co elements with d<13μm, only single magnetic vortex states are found, whereas for d>13–15μm, magnetic multivortex and antivortex states are observed.