Magnetization curves of a spin- [formula omitted] bilayer system (A 2) (A pB 1− p) 1 (B) 2 with disordered interfaces

Abstract

A calculation is presented for the component magnetizations of an infinite multilayer Ising system, consisting periodically of two layers of spin- 1 2 A ions, two layers of spin- 1 2 B ions, and a disordered layer interface in between that is characterized by a random arrangement of A and B ions like a two-dimensional A p B 1− p alloy. The system is a simple cubic Ising-type structure with a coordination number z = 6. The model is general for ferro- and for antiferromagnetic A-B exchange couplings. The A-A and B-B exchange couplings are regarded as ferromagnetic. An effective field theory that goes beyond mean field, is employed to calculate the bulk-like transition temperature, the different component magnetizations as well as the total bulk-like magnetization. The component magnetizations are calculated for different realistic model values of ferro- and antiferromagnetic A-B exchange constants, as a function of temperature and of the concentration parameter p that characterizes the disorder in the interface. We show that the presence of a disordered interface may significantly affect the component and total magnetizations. In particular, for the case of antiferromagnetic exchange couplings, it is shown that the system can acquire a compensation temperature for certain domains of values of the concentration parameter p in the disordered interface.