Ferromagnetism with high magnetoresistance in Ag decorated graphitic carbon nitride

Abstract

Origin of ferromagnetism across the interface of two different diamagnets is an important issue in the magnetism of 2D materials in condensed matter physics. In recent years, a number of theoretical results have been reported on the magnetism of graphitic carbon nitride however the experimental verification is not well established. In the present work, graphitic carbon nitride (g-C3N4) has been decorated with silver nanoparticles to investigate the induced magnetic moment in diamagnetic g-C3N4 due to proximity effect of ultrafine conducting islands (Ag) grown on the surface of g-C3N4 and the interaction at the interface. Here Ag atoms act as n-type donor and each donor atom injects electron to the pz orbital of N atom. Due to charge transfer effect, localized holes are generated in Ag 4d orbitals, which show strong ferromagnetic ordering with coercivity (~1325) in the composite system. Very interesting Mott-type transition from metal to insulator (M−I) is observed. This complex nature of charge transport is explained by electron-electron interaction in the insulating region and electron scattering in the metallic region. Accordingly, the magnetotransport (MR) study also shows an interesting transition from positive magnetoresistance to negative magnetoresistance. In the hopping region, the positive MR is explained by wave function shrinkage model where the negative MR is due to quantum interference effect. In particular, this correlated magnetic and electric responses cause the Ag nanoclusters decorated graphitic carbon nitride system a potential candidate for future spintronic application.