Interacting ferromagnetic nanoparticles in discontinuous Co80Fe20/Al2O3 multilayers:: From superspin glass to reentrant superferromagnetism -: art. no. 134423

Dipolar superferromagnetism with reentrant low-temperature superspin glass behavior is observed on a randomly distributed ferromagnetic nanoparticle systems in discontinuous metal-insulator multilayers [Co80Fe20(t)/Al2O3(3 nm)](10) with nominal thickness 1.1 less than or equal to t less than or equal to1.3 nm by use of ac susceptometry and dc magnetometry. At t = 1.0 nm, superspin glass-like freezing is evidenced by the criticality of dynamic and nonlinear susceptibilities.