Magnetization plateaus in the ferromagnetic-ferromagnetic-antiferromagnetic Ising chain

TL;DR

This paper analyzes the magnetization behavior of a ferromagnetic-ferromagnetic-antiferromagnetic Ising chain under an external magnetic field, revealing conditions for magnetization plateaus and their underlying spin structures.

Contribution

It provides an explicit thermodynamic description of the model and identifies the origin of magnetization plateaus related to stable spin configurations.

Findings

Magnetization curve exhibits a plateau at 1/3 of saturation for strong antiferromagnetic coupling.

The plateau is caused by the stability of the <3111> spin structure.

Width of the plateau is determined at zero temperature.

Abstract

The Ising chain consisting of the antiferromagneticaly coupled ferromagnetic trimer is considered in the external magnetic field. In the framework of the transfer-matrix formalism the thermodynamics of the system is described. The magnetization per site (m) is obtained as the explicit function of the external magnetic field (H). The corresponding plots of m(H) are drawn. Two qualitatively different regions of the values of coupling constants are established: weak antiferromagnetic coupling (J_A<3J_F) and the strong antiferromagnetic coupling $(J_A\geq3J_F)$. For the latter case the magnetization curve with plateau at $m/m_{sat}=1/3$ is obtained. It is proven that the plateau is caused by the stability of spatially modulated spin structure <3111>. The values of magnetic field determining the width of the plateau are obtained in the limit of zero temperature.