Surface Incommensurate Structure in an Anisotropic Model with competing interactions on Semiinfinite Triangular Lattice

TL;DR

This paper investigates an anisotropic spin model on a semi-infinite triangular lattice, revealing complex phase behavior including incommensurate structures both in the bulk and near the surface, with temperature-dependent phenomena.

Contribution

It introduces a detailed phase diagram for the model and uncovers novel surface and subsurface incommensurate structures influenced by temperature.

Findings

Bulk incommensurate structure modulated along competing interactions

Surface incommensurate structure varies with temperature

Discovery of a new subsurface incommensurate structure at low temperatures

Abstract

An anisotropic spin model on a triangular semiinfinite lattice with ferromagnetic nearest-neighbour interactions and one antiferromagnetic next-nearest-neighbour interaction is investigated by the cluster transfer-matrix method. A phase diagram with <2> antiphase, ferromagnetic, incommensurate, and disordered phase is obtained. The bulk uniaxial incommensurate structure modulated in the direction of the competing interactions is found between the <2> antiphase and the disordered phase. The incommensurate structure near the surface with free and <2> boundary condition is studied at different temperatures. Paramagnetic damping at the surface and enhancement of the incommensurate structure in the subsurface region at high temperatures and a new subsurface incommensurate structure modulated in two directions at low temperatures are found.