ANISOTROPIC DOMAIN EVOLUTION IN EPITAXIAL FE GAAS(001) WIRES/

The magnetization reversal in in-plane magnetized epitaxial Fe/GaAs(00 1) wire elements with dimensions of 15 mu m (width w) x 500 mu m (leng th l) x 300 Angstrom (Thickness t) has been studied by scanning Kerr m icroscopy and Kerr magnetometry. The two-jump switching process is obs erved which is characteristic for the magnetization reversal in contin uous epitaxial Fe(001) films with fourfold in-plane anisotropy. Howeve r, in contrast to the continuous film, the domain nucleation and growt h processes which mediate the irreversible magnetization jumps at the two critical fields, H-c1 and H-c2 are found to be determined by the o rientation of the applied field with respect to the long and the short wire axis. This anisotropy in the domain evolution is a result of the combined effects of local edge dipolar fields, the fourfold magnetocr ystalline anisotropy as well as the finite and anisotropic lateral ext ensions of the wires. Due to the large aspect ratio of l/w, the bounda ries of the long and short wire edges restrict the domain expansion di fferently. Consequently, this ''shape'' anisotropy in the domain evolu tion contrasts with the conventional shape anisotropy associated with macroscopic (average) demagnetization fields.