Metastable states influence on the magnetic behavior of the triangular lattice: Application to the spin-chain compound Ca3Co2O6

TL;DR

This study uses Monte Carlo simulations to reveal how metastable states cause the splitting of the magnetization plateau in Ca3Co2O6, aligning well with experimental observations and highlighting the role of out-of-equilibrium states.

Contribution

It introduces a simple frozen-moment model with large Ising spins to explain the thermal and magnetic behavior of Ca3Co2O6, emphasizing metastable states' influence.

Findings

Metastable states cause the splitting of the 1/3 magnetization plateau.

Simulated magnetization curves match experimental data across different sweep rates.

Domain-wall structures are responsible for the observed plateau behavior.

Abstract

It is known that the spin-chain compound Ca3Co2O6 exhibits very interesting plateaus in the magnetization as a function of the magnetic field at low temperatures. The origin of them is still controversial. In this paper we study the thermal behavior of this compound with a single-flip Monte Carlo simulation on a triangular lattice and demonstrate the decisive influence of metastable states in the splitting of the ferrimagnetic 1/3 plateau below 10 K. We consider the [Co2O6]n chains as giant magnetic moments described by large Ising spins on planar clusters with open boundary conditions. With this simple frozen-moment model we obtain stepped magnetization curves which agree quite well with the experimental results for different sweeping rates. We describe particularly the out-of-equilibrium states that split the low-temperature 1/3 plateau into three steps. They relax thermally to the 1/3 plateau, which has long-range order at the equilibrium. Such states are further analyzed with snapshots unveiling a domain-wall structure that is responsible for the observed behavior of the 1/3 plateau. A comparison is also given of the exact results in small triangular clusters with our Monte Carlo results, providing further support for our thermal description of this compound.