Probing magnetization dynamics of strongly interacting magnetic nanoparticles through magnetoresistive current noise measurements

The dependence of tunnelling current fluctuations on temperature and magnetic field was studied in an organically capped magnetite (Fe₃O₄) nanocrystal (NC) array deposited between 30 nm spaced gold electrodes. Low-frequency Lorentzian (random telegraph) noise was observed around the magnetization freezing temperature due to magnetic moment switching of the NCs under zero magnetic fields, diminishing with a saturating magnetic field. The temperature dependence of current fluctuations followed the temperature dependence of magnetic susceptibility. This work offers a new tool for locally studying collective magnetization dynamics in strongly interacting magnetic NC arrays.