Fingerprints of super spin-glass state in two-dimensional nanoscopic system

Abstract

Novel two-dimensional magnetic assembly was designed, manufactured, and its static and dynamic magnetic response was investigated. The assembly contains Fe3O4 nanoparticles of nominal size 7 nm which were deposited on plasma-treated polypropylene substrate using a grafting technique. The nanoparticles create agglomerates with size distribution ranging nominally from 10 nm to 110 nm. The temperature dependence of zero-field and field-cooled susceptibility is consistent with glassy behavior. The relative shift of maximum in alternating susceptibility Γ ≈ 0.075 and zυ = 10 obtained from critical slowing down analysis also support the formation of the collective states akin to super spin-glass. However, the absence of collapse in dynamic scaling of alternating susceptibility data using predictions for three-dimensional spin-glass with Gaussian distribution of magnetic coupling and two-dimensional bimodal spin-glass suggests that the studied system is not representative of the used limiting models. The investigation of memory effects revealed the coexistence of relaxation phenomena of collective degrees of freedom and individual nanoparticles. The obtained results suggest that the studied assembly is appropriate for the investigation of super spin-glass state in two-dimensional magnetic system with dominant dipolar interaction.