Interface effects on the critical temperature of heterostructures of magnetic films

The analytical approach to the critical point of Ising films proposed recently by Lin et al is extended to investigate the interface effects on the critical temperature T_c for magnetic bilayer heterostructures. We consider heterostructures composed of an m-monolayer film grown on a substrate of an n-monolayer magnetic film with different lattice structures where 1 ≤ m and n ≤ ∞. The mean T_c(m, n) of the bilayered heterostructure as a whole is obtained as a function of the total thickness N = m + n of the inhomogeneous system. A strong dependence of the critical temperature upon the lattice structure is revealed. In particular, interface effects on T_c for systems consisting of an overlayer of a few spin monolayers on a thin film of magnetic substrates with different lattice structure are investigated in detail and results for various combinations of the lattice structure are discussed.