Memory effects and magnetic interactions in a g-Fe2O3 nanoparticle system

The low-temperature dynamics of a magnetic nanoparticle system sg-Fe2O3—alginate nanocomposite with average particle size around 4 nmd have been studied by superconducting quantum interference device measurements. Using different temperature and field protocols, memory phenomena in the dc magnetization and magnetic relaxation have been observed at temperatures below its blocking temperature TB=37 K. However, aging experiments show an absence of any waiting time dependence in the magnetization relaxation. These observations indicate that the dynamics of this nanoparticle system are governed by a wide distribution of particle relaxation times which arise from the distribution of particle sizes and weak interparticle interactions. © 2005 American Institute of Physics. fDOI: 10.1063/1.1853898g