A numerical investigation of entropy changes in superparamagnetic nanocomposite systems

The Event Driven Monte Carlo (EDMC) technique was used to simulate the dynamics of fabrication of superparamagnetic nanocomposites with nanosized particles (magnetic particles dispersed in a non-magnetic matrix). The entropy change of the composites was studied. The random positioning and migration of the particles result in the formation of chains that have the magnetic particles in contact. The results show that the chain distribution and entropy change of the composite system are very sensitive to substrate temperature. For a given dilution, the lower the temperature, the less the chain formation and the larger the entropy change. Unipolar electrostatic charging of magnetic particles was proposed to decrease the reduction in entropy change due to chain formation. The simulation results show that the reduction in entropy change due to chain formation decreases significantly. Due to the electrostatic charging, the entropy change of the nanocomposite is relatively constant and is insensitive to temperature. The detailed description of the EDMC technique is presented in the Appendix.