Ac susceptibility studies of discontinuous Co80Fe20Al2O3 multilayers

Discontinuous metal}insulator multilayers [Co Fe (t)/Al O (3 nm)] are prepared by ion-beam sputtering and investigated by SQUID magnetometry and AC susceptometry. For 1.0)t)1.6 nm, two coexisting subsystems of dipolar coupled nanoparticles are encountered. While a spin-glass-like freezing particulate fraction dominates at t"1.0 nm, a percolating dipolar ferromagnetic fraction becomes increasingly important at higher nominal thickness of t. 2001 Elsevier Science B.V. All rights reserved.