Phase diagrams and critical behaviours of the mixed spin-5/2 and spin-7/2 Ising system

Abstract

We used mean-field theory based on the Bogoliubov inequality for the Gibbs free energy to examine the mag- netic properties of a mixed spin-5/2 and spin-7/2 Blume-Capel ferrimagnetic system. The thermal behaviours of the system magnetization are classified according to the extended Néel nomenclature. The system exhibits compensation phenomena where a complete cancellation of sublattice magnetizations is observed below the critical temperature. Temperature-dependent phase diagrams are constructed for the case of unequal sublat- tice crystal field interactions. Under appropriate conditions, our calculations reveal first-order transitions in addition to second-order ones previously observed in Monte Carlo simulations.