Interaction between magnetic nanoparticles in clusters

Micromagnetic simulations are often used to model the magnetic properties of nanoparticles, depending on their shape and dimension as well as other parameters. Due to the significant increase in computing time for large-scale models, simulations are regularly restricted to a single magnetic nanoparticle. Applications in bit-patterned media etc., however, necessitate large clusters of nanostructures. In our recent works, the deviations of magnetic properties and magnetization reversal processes, comparing single nanoparticles and small clusters, were investigated using the micromagnetic simulation OOMMF. The studies concentrated on a special fourfold shape which has been shown before to offer four stable states at remanence, allowing for creating quaternary bit-patterned media with two bits storable in one position. The influence of downscaling was examined by varying the sample dimensions without changing the particle shape. The results show that in case of the special square nanostructures under investigation, the largest nanoparticles experience the strongest effect by being included in a cluster, while the technologically more relevant smaller nanoparticles have similar magnetic properties and identical magnetization reversal processes for single and clustered particles.