Magnetic properties of A_k(A_pB_1-p)₁B_h superlattices containing alloy disordered interfaces in a spin-1/2 model

An Ising model is presented for a simple cubic-type structure, to determine the magnetic properties for superlattices of periodic A_k (A_pB_1-p)₁B_h formula consisting of k layers of spin-1/2 A ions, h layers of spin-1/2 B ions and single layer disordered alloy interfaces between them. The interface layers are characterized by random arrangements of A and B ions so that (A_pB_1-p)₁ is a two-dimensional thermodynamically stable alloy. The magnetic properties studied concern notably the phase diagrams and the sublattice magnetizations of these systems. The model is general and can be used for ferro- or anti-ferromagnetic A-B exchange couplings. In this paper the A-A and B-B exchange couplings are considered ferromagnetic with no loss of generality. An effective field theory is employed to calculate the properties of these systems. We apply the method to various Fe_k(Fe_p Tb_1-p)₁ Tb_h superlattices. The needed exchange constants for the two-dimensional alloy interface are calculated in the framework of this model, and used to calculate these properties for different concentrations 0 ≤ p ≤ 1, for these superlattices. The architecture and concentration dependence of the magnetic properties is an important feature of this paper, allowing a useful experimental analysis of similar systems.