Magnetostatic coupling of free poles in nanostructured cells of an exchange-coupled trilayer

The magnetostatic coupling of free poles formed on the surfaces of the nanostructured cells of an exchange-coupled trilayer is examined by calculating the magnetostatic fields for the two different cases of antiparallel and parallel magnetization alignments. The lateral dimensions of the cells were varied greatly from 160 nm (long axis) × 80 nm (short axis) to 100 nm × 50 nm. We found that the coupling of free poles was strong in the region close to the alternating layer and close to the center of the short axis. The results for the cell size dependence showed that the highest coupling strength was observed for a cell size of 140 nm × 70 nm when the magnetizations in the two magnetic layers were aligned antiparallel. In the parallel alignment, however, the coupling strength increased with increasing cell size. These results are discussed in terms of the rigidity of the magnetic configuration as a function of the cell size.