Study of the Critical Behavior and the Multi-Layer Transition in a Spin-1 Ashkin–Teller Model under the Effect of the RKKY Interaction: Finite-Size-Scaling and Monte Carlo Studies

Abstract

By using a Monte Carlo simulation, we have studied the effects on the multilayer transition and magnetic properties of the crystal field [Formula: see text], the four-spin coupling [Formula: see text] and RKKY interaction in the spin-1 Ashkin–Teller (AT) model of a system composed of two magnetic multi-layer materials, of various thicknesses, separated by a nonmagnetic spacer of thickness [Formula: see text]. By varying the strength of [Formula: see text], we have obtained a new partially ordered phase [Formula: see text], for different values of [Formula: see text]. We have established a rich phase diagram with first and second-order phase transitions with tricritical points. It is shown that the transition temperature of both magnetic blocks depends strongly on the thickness of the magnetic layers [Formula: see text], as well as [Formula: see text] and [Formula: see text]. There exists a critical thickness of the magnetic layers [Formula: see text] above which the multilayer blocks undergo a transition separately at different temperatures, for a high value of [Formula: see text] and [Formula: see text]. Besides, the critical exponents are computed.