Triangular Heisenberg antiferromagnets are prototypes of geometric frustration, even if for nearest-neighbor interactions quantum fluctuations are not usually strong enough to destroy magnetic ordering: stronger frustration is required to stabilize a spin-liquid phase. On the basis of static magnetization and electron spin resonance measurements, we demonstrate the emergence of j~eff=21 moments in the triangular-lattice magnet Na2BaCo(PO4)2. These moments are subject to an extra source of frustration that causes magnetic correlations to set in far above both the magnetic ordering and Weiss temperatures. Corroborating the j~eff=21 ground state, theory identifies ferromagnetic Kitaev exchange anisotropy as additional frustrating agent, altogether putting forward Na2BaCo(PO4)2 as a promising Kitaev spin-liquid material.
@article{arxiv.2106.02437,
title = {Frustration enhanced by Kitaev exchange in a $\boldsymbol{\tilde{j}_{\text{eff}}=\frac12}$ triangular antiferromagnet},
author = {C. Wellm and W. Roscher and J. Zeisner and A. Alfonsov and R. Zhong and R. J. Cava and A. Savoyant and R. Hayn and J. van den Brink and B. Büchner and O. Janson and V. Kataev},
journal= {arXiv preprint arXiv:2106.02437},
year = {2021}
}