A comparative analysis of the critical and compensation behaviours of two mixed-spin AA- and AB-stacked bilayer graphenes under defect

The stacking of graphenes with targeted defects could potentially be an asset for emerging technologies exceeding the inherent limitations of monolayer graphene. We use here the finite cluster approximation to derive insight into the phase diagrams and the magnetisations of two defective AA – and AB-stacked bilayer graphenes (BLGs), where mixed spin-3/2 and spin-1 occupying each layer interact ferrimagnetically via a diluted bond Jσs. The AA-stacked (BLG) exhibits the second-order with a reentrant transition at low temperatures; meanwhile, the AB-stacked (BLG) undergoes always a tricritical behaviour with compensation temperatures emerging under modest dilution p in small Jσs-intervals. The insertion of the crystal fields DS and Dσ acting on the spin-1 and spin-3/2 plays respectively a relevant role in the appearance of the tricritical behaviour in both structures and the compensation phenomena only for the AA-stacking structure. Finally, under a uniform crystal field (DS = Dσ), the order of the AB-stacked (BLG) may disappear at a critical bond threshold pc.