Hysteresis in a linear chain of magnetic nanoparticles

Abstract

We perform kinetic Monte Carlo simulation to study the magnetic hysteresis in a one-dimensional chain of magnetic nanoparticles (MNPs). The hysteresis behavior is systematically analyzed as a function of several key parameters: anisotropy axis orientation, dipolar interaction strength λ, frequency ν of the applied magnetic field, and temperature T. The anisotropy axes of all the MNPs are assumed to make an angle α with the chain axis. In the absence of dipolar interaction and thermal fluctuations, the hysteresis follows the Stoner–Wohlfarth model as expected. Extremely weak hysteresis is observed with small values of dipolar interaction strength for ν=105Hz and T=300K. On the other hand, there is a significant hysteresis even for weakly interacting MNPs with ν=109Hz. The hysteresis properties are strongly dependent on these parameters. Due to an increase in the ferromagnetic coupling, the hysteresis loop area increases with λ. The coercive field Hc and the amount of heat dissipated EH due to hysteresis decrease rapidly with α and T for small values of λ and ν=105Hz, while for large λ, they fall very slowly. When ν is very large (=109Hz), EH and Hc are found to have negligible dependence on T irrespective of λ. The results with a small value of frequency should be taken into account in the interpretation of the experiments and efficient usage of magnetic hyperthermia.