Approaching the ground state of the kagome antiferromagnet

TL;DR

This study investigates the magnetic ground state of a kagome antiferromagnet using neutron scattering, revealing short-range chiral order and negligible interlayer coupling, consistent with theoretical predictions.

Contribution

It provides experimental evidence for a two-dimensional coplanar ground state with staggered chirality in a kagome antiferromagnet, confirming theoretical models.

Findings

No three-dimensional long-range antiferromagnetic order

Short-range chiral order observed in the kagome layers

Consistent with Monte Carlo simulations of the ground state

Abstract

Y{0.5}$Ca{0.5}BaCo4O7 contains kagome layers of Co ions, whose spins are strongly coupled according to a Curie-Weiss temperature of -2200 K. At low temperatures, T = 1.2 K, our diffuse neutron scattering study with polarization analysis reveals characteristic spin correlations close to a predicted two-dimensional coplanar ground state with staggered chirality. The absence of three dimensional long-range AF order proves negligible coupling between the kagome layers. The scattering intensities are consistent with high spin S=3/2 states of Co2+ in the kagome layers and low spin S=0 states for Co3+ ions at interlayer sites. Our observations agree with previous Monte Carlo simulations indicating a ground state of only short range chiral order.