Spin-phonon coupling induced frustration in the exactly solved spin-1/2 Ising model on a decorated planar lattice

TL;DR

This paper investigates how spin-phonon coupling in a decorated spin-1/2 Ising model induces frustration and complex phase behavior, revealing a partially ordered-disordered phase and diverse thermal properties.

Contribution

It introduces an exactly solvable model showing how magnetoelastic interactions create effective antiferromagnetic frustration and novel phases in decorated lattices.

Findings

Spin-phonon coupling induces effective antiferromagnetic next-nearest-neighbour interactions.

A partially ordered and disordered phase emerges due to frustration.

Temperature dependence of specific heat shows diverse magnetic and lattice contributions.

Abstract

The spin-1/2 Ising model with a spin-phonon coupling on decorated planar lattices partially amenable to lattice vibrations is examined within the framework of the generalized decoration-iteration transformation and the harmonic approximation. It is shown that the magnetoelastic coupling gives rise to an effective antiferromagnetic next-nearest-neighbour interaction, which competes with the nearest-neighbour interaction and is responsible for a frustration of the decorating spins. The strong enough spin-phonon coupling consequently leads to an appearance of the striking partially ordered and partially disordered phase, where a perfect antiferromagnetic alignment of the nodal spins is accompanied with a complete disorder of the decorating spins. The diversity in temperature dependences of the total specific heat is investigated in connection with the particular behaviour of its magnetic and lattice contribution.