Magnetic Shape Anisotropy in Chemically Synthesized Chains of Nickel Nanoparticles

We present the magnetization reversal dynamics in one-dimensional chains of single domain nickel nanoparticles of about 50 nm diameters. Experimental results show that the magnetization reversal is mainly governed by the overall shape of the chains and typical easy-axis and hard-axis like magnetic hysteresis loops are observed when magnetic field is applied parallel and perpendicular to the length of the chains. Micromagnetic simulations on a single nickel chain composed of 20 nickel nanoparticles show reasonable qualitative agreement with the experimental results. In this case the magnetization reversal starts from the edges of the chain and progresses towards the center. However, simulations with three parallel nickel chains show that the reversal mechanism is modified into complicated pattern formation and appearance of local flux closure due to the magnetostatic interactions between the chains. A better qualitative agreement with the experimental results is obtained for this case.