Novel ordering of the pyrochlore Heisenberg antiferromagnet with the ferromagnetic next-nearest-neighbor interaction

TL;DR

This study uses Monte Carlo simulations to explore how a classical pyrochlore Heisenberg antiferromagnet with ferromagnetic next-nearest-neighbor interactions undergoes a first-order phase transition into a unique ordered state with long-range Fourier amplitude order but fluctuating phases.

Contribution

It reveals a novel ordered state characterized by long-range Fourier amplitude order with phase fluctuations, induced by ferromagnetic next-nearest-neighbor interactions.

Findings

First-order transition at finite temperature

Long-range order in Fourier amplitude with phase fluctuations

Unique ordered state with period four spin structure

Abstract

The ordering property of the classical pyrochlore Heisenberg antiferromagnet with the ferromagnetic next-nearest-neighbor interaction is investigated by means of a Monte Carlo simulation. The model is found to exhibit a first-order transition at a finite temperature into a peculiar ordered state. While the spin structure factor, i.e., the thermal average of the squared Fourier amplitude of the spin, exhibits a finite long-range order characterized by the commensurate spin order of the period four, the thermal average of the spin itself almost vanishes. It means that, although the amplitude of the spin Fourier component is long-range ordered, the associated phase degree of freedom remains to be fluctuating.