The characteristics of patterned CoFeB films have attracted much attention for spin configurations and magnetization processes of nanostructured elements in that CoFeB has desirable properties including magnetic softness, large magneto-impedance, high spin polarization, and epitaxial registry with MgO(100). In this experiment, micron-sized CoFeB islands with various thicknesses, deposited by a sputtering process, were investigated in order to study their slow micro-magnetic properties as a function of an externally applied magnetic field as well as their remanent domain configurations.

Magnetic Force Microscopy (MFM) of the array at zero applied field revealed that despite a large variation in CoFeB thickness, the remanent domain configurations could be classified into several unique domain configurations. Selected islands of dimensions from 0.25µm x 0.25µm to 16µm x 16µm were studied using MFM equipment.

In addition, the creation and annihilation of magnetic vortex and antivortex pairs in cross-tie walls on CoFeB islands of 16 µm x 4 µm were investigated using MFM in the presence of an applied field. The first vortex-antivortex pair is nucleated in a 4-domain Landau pattern from a section of a 180 degree Néel wall as a consequence of the formation of an end domain closure pattern. The vortex-antivortex pair creation satisfies the condition that the closure domain vortices have the same chiralities. Pair annihilation was found to occur in two steps: a rapid advance of the vortices toward the more or less fixed antivortices followed by a deceleration caused by the decrease in local susceptibility. There is a spread in the annihilation fields that does not depend upon the core polarity but is determined by energy minimization.