Rectangular lattices of permalloy nanoparticles: Interplay of single-particle magnetization distribution and interparticle interaction

Regular two-dimensional rectangular lattices of permalloy nanoparticles (40 nm in diameter) were prepared by electron lithography. The magnetization curves were studied by differential Hall magnetometry for different external field orientations at 4.2 and 77 K. The shape of the hysteresis curves indicates that there is magnetostatic interaction between the particles The main peculiarity of the system is the existence of remanent magnetization perpendicular to the easy plane. By numerical simulation it is shown that the feature of the magnetization reversal is a result of the interplay of the interparticle interaction and the magnetization distribution within the particles (vortex or uniform).