Low-temperature properties of classical zigzag spin chain at the ferromagnet-helimagnet transition point

TL;DR

This paper investigates the low-temperature thermodynamics of a classical frustrated ferromagnetic spin chain at the critical transition point, revealing specific power-law behaviors of correlation length and susceptibility, and comparing results with experimental observations.

Contribution

It provides an exact analysis of the classical spin chain at the transition point using continuum mapping, deriving explicit temperature dependencies of key thermodynamic quantities.

Findings

Correlation length scales as T^{-1/3} at the transition point.

Magnetic susceptibility diverges as T^{-4/3} at the transition point.

Susceptibility exhibits a maximum near the transition in the helical phase.

Abstract

Low-temperature thermodynamics of the classical frustrated ferromagnetic spin chain near the ferromagnet-helimagnet transition point is studied by means of mapping to the continuum limit. The calculation of the partition function and spin correlation function is reduced to quantum problem of a particle in potential well. It is shown that exactly at the transition point the correlation length behaves as $T^{-1/3}$ and the magnetic susceptibility diverges as $T^{-4/3}$ in the low-temperature limit. Corresponding numerical factors for the correlation length and the susceptibility is calculated. It is shown that the low-temperature susceptibility in the helical phase near the transition point has a maximum at some temperature. Such behavior as well as the location and the magnitude of the maximum as a function of deviation from the transition point are in agreement with that observed in several materials described by the quantum $s=1/2$ version of this model.