Monte Carlo study of the surface effect on the compensation and critical behaviour in a molecular-based magnetic film AFeIIFeIII(C2O4)3

Abstract

Monte Carlo simulation is used to study the magnetic properties and critical behaviour of a molecular-based magnetic film AFeIIFeIII(C2O4)3(A = N(n − CnH2n+1)4, n = 3–5). The effects of surface exchange coupling, surface single-ion anisotropy and layer thickness on the compensation temperature and critical temperature of a ferrimagnetic mixed spin-2 and spin-5/2 Ising model on a honeycomb lattice are discussed in detail. The results show that the surface intralayer exchange coupling R1 = J1S/|J1| and surface interlayer exchange coupling R2 = J2S/|J1| play important roles in the compensation and critical behaviour of the system. In particular, we have found two special points R1c at which the compensation and critical temperatures are independent of the layer thickness L and the surface single-ion anisotropy D1S/|J1|. A number of characteristic phenomena, such as the possibility of two and three compensation points, are found. The effects of the layer thickness L on the susceptibility, internal energy and specific heat with temperature are numerically investigated.