Reduced magnetization curves of Ising nanoparticles with high critical temperature

The magnetic properties (phase diagram, the thermal variations of magnetization and the reduced magnetization curve) in graphene-like Ising nanoparticles are examined by the effective-field theory with correlations. The effects of surface exchange interaction J(S) on the magnetic properties are discussed. When J(S) is larger than the critical value J(SC), a nanoparticle with high critical temperature is possible. The value of J(SC) depends on the shape and the degree of structural packing of the nanoparticle. It is found that there exist two types of reduced magnetization curves for a nanoparticle with J(S) > J(SC).