Magnetization reversal of a multilayered FeGd dot array imaged by transmission x-ray microscopy

The magnetization reversal of an array of 1 mum squared FeGd dots has been studied by magnetic transmission x-ray microscopy (MTXM). A (4 Angstrom Fe/ 4 Angstrom Gd) x 75 multilayered FeGd system has been prepared on a 30 nm t hin Si3N4 membrane by sputtering and structured by optical lithography and ion beam etching techniques. Both the domain structure within each single d ot and the collective switching behavior could be observed with MTXM. A lar ge variation in the nucleation field of the dots was found and can be attri buted to the shape of the dots. A correlation between the nucleation field and the perimeter of each dot could be deduced. Hysteresis loops of individ ual dots are derived, taking into account the proportionality of the dichro ic contrast to the magnetization of the sample. The stepped profile of the magnetization loop of a single dot is found to be clearly distinct from a c ontinuous film. The high lateral resolution and the possibility to record t he images in varying external magnetic fields proves that MTXM is a highly adapted tool to investigate nanostructured magnetic systems. (C) 2001 Ameri can Institute of Physics.