Controlling local relaxation in small clusters of magnetic nanoparticles

Abstract

We investigate the local (particle level) and averaged magnetic relaxation characteristics in linear chain-like agglomerates of k magnetic nanoparticles (MNPs) or k-mers using computer simulations. The local relaxation behaviour is dictated by the corresponding dipolar field acting on the nanoparticle, irrespective of k-mer size. There is a wide variation in local relaxation characteristics as a function of nanoparticle position in a small nanocluster. On the other hand, there is more uniformity in the local relaxation response with a larger k-mer, except for MNPs at the boundary. Interestingly, there is a smooth decay of magnetization with small hd, independent of cluster size. In contrast, the magnetization ceases to relax in the presence of substantial dipolar interaction strength. Remarkably, the local Néel relaxation time τNi is directly proportional to the corresponding dipolar field. Likewise, the averaged Néel relaxation time τN also depends strongly on the k-mer size and hd.