By means of a combined x-ray diffraction, magnetic susceptibility and specific heat study, we investigate the interplay between orthorhombic distortion and stripe-like antiferromagnetic (AFM) order in the Mott insulator BaCoS2 at TN=290 K. The data give evidence of a purely electronic AFM transition with no participation of the lattice. The observation of large thermal fluctuations in the vicinity of TN and a Schottky anomaly unveils competing ground states within a minute ∼1 meV energy range that differ in the orbital and spin configurations of the Co ions. This interpretation suggests that the stripe-like order results from a spontaneous symmetry breaking of the geometrically frustrated pristine tetragonal phase, which offers an ideal playground to study the driving force of multi-orbital Mott transitions without the participation of the lattice.
@article{arxiv.2302.12208,
title = {Two-dimensional fluctuations and competing phases in the stripe-like antiferromagnet BaCoS$_2$},
author = {Haneen Abushammala and Benjamin Lenz and Benoit Baptiste and David Santos-Cottin and Pierre Toulemonde and Michele Casula and Yannick Klein and Andrea Gauzzi},
journal= {arXiv preprint arXiv:2302.12208},
year = {2023}
}