Double exchange model on triangular lattice: non-coplanar spin configuration and phase transition near quarter filling

TL;DR

This paper investigates the phase transitions and spin configurations in a double exchange model on a triangular lattice, revealing a non-coplanar intermediate phase and the effects of temperature and interactions near quarter filling.

Contribution

It introduces a detailed analysis of non-coplanar spin phases and phase transitions in a frustrated lattice model using polynomial expansion and Monte Carlo methods.

Findings

Non-coplanar spin configuration acts as an intermediate phase.

Phase transition from ferromagnetic to non-coplanar and 120-degree spin phases.

Temperature influences magnetic structure and phase stability.

Abstract

Unconventional anomalous Hall effect in frustrated pyrochlore oxides is originated from spin chirality of non-coplanar localized spins, which can also be induced by the competition between ferromagnetic (FM) double exchange interaction $J_{H}$ and antiferromagnetic superexchange interaction $J_{AF}$. Here truncated polynomial expansion method and Monte Carlo simulation are adopted to investigate the above model on two-dimensional triangular lattice. We discuss the influence of the range of FM-type spin-spin correlation and strong electron-spin correlation on the truncation error of spin-spin correlation near quarter filling. Two peaks of the probability distribution of spin-spin correlation in non-coplanar spin configuration clearly show that non-coplanar spin configuration is an intermediate phase between FM and 120-degree spin phase. Near quarter filling, there is a phase transition from FM into non-coplanar and further into 120-degree spin phase when $J_{AF}$ continually increases. Finally the effect of temperature on magnetic structure is discussed.