Ba8CoNb6O24: a spin-1/2 triangular-lattice Heisenberg antiferromagnet in the 2D limit

TL;DR

This study investigates Ba8CoNb6O24, a layered material that closely realizes a 2D spin-1/2 triangular Heisenberg antiferromagnet, showing no long-range order down to very low temperatures, thus providing a near-ideal platform for studying quantum magnetism.

Contribution

The paper provides experimental and theoretical evidence that Ba8CoNb6O24 is a near-perfect 2D spin-1/2 triangular Heisenberg antiferromagnet with no detectable anisotropy or magnetic order at very low temperatures.

Findings

Ba8CoNb6O24 exhibits no long-range magnetic order down to 0.06 K.

The material closely realizes the ideal 2D spin-1/2 triangular Heisenberg model.

Susceptibility, specific heat, and neutron scattering confirm its 2D magnetic nature.

Abstract

The perovskite Ba8CoNb6O24 comprises equilateral effective spin-1/2 Co2+ triangular layers separated by six non-magnetic layers. Susceptibility, specific heat and neutron scattering measurements combined with high-temperature series expansions and spin-wave calculations confirm that Ba8CoNb6O24 is basically a twodimensional (2D) magnet with no detectable spin anisotropy and no long-range magnetic ordering down to 0.06 K. In other words, Ba8CoNb6O24 is very close to be a realization of the paradigmatic spin-1/2 triangular Heisenberg model, which is not expected to exhibit symmetry breaking at finite temperature according to the Mermin and Wagner theorem.