Hysteresis in a linear chain of magnetic nanoparticles

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 lambda, frequency nu of the applied magnetic field, and temperature T. The anisotropy axes of all the MNPs are assumed to make an angle alpha with the chain axis. In the absence of dipolar interaction and thermal fluctuations, the hysteresis follows the StonerWohlfarth model as expected. Extremely weak hysteresis is observed with small values of dipolar interaction strength for nu = 10(5) Hz and T = 300 K. On the other hand, there is a significant hysteresis even for weakly interacting MNPs with nu = 10(9) Hz. The hysteresis properties are strongly dependent on these parameters. Due to an increase in the ferromagnetic coupling, the hysteresis loop area increases with lambda. The coercive field Hc and the amount of heat dissipated E-H due to hysteresis decrease rapidly with alpha and T for small values of lambda and nu = 10(5) Hz, while for large lambda, they fall very slowly. When. is very large (=10(9) Hz), EH and H-c are found to have negligible dependence on T irrespective of lambda. 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. Published under license by AIP Publishing.