Transition from Non-PercolatedSuperferromagnetism to PercolatedFerromagnetism in Granular Metal-InsulatorMultilayers

摘要

The magnetic properties and electrical resistance of nanoparticle systems rosoFe20(t_nYAl_2O_3(3 nm)]m are investigated. The temperature dependence of the coercive field for different samples with different t_n shows a sudden jump at the nominal thickness 1.4 nm, showing a clear transition from superferromagnetism between nanoparticles in the non-percolating regime to conventional thin film ferromagnetism at percolating concentration.