AC susceptibility studies of discontinuous Co80Fe20/Al2O3 multilayers

Abstract Discontinuous metal–insulator multilayers [Co 80 Fe 20 ( t )/Al 2 O 3 (3 nm)] 10 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 .