We present magnetization and dilatometry measurements on the honeycomb cobaltate Na3Co2SbO6 and map out its detailed field-temperature phase diagram down to sub-Kelvin temperatures. Our data for in-plane magnetic fields show a strongly anisotropic c∗-axis lattice response, which is dominated by the variation of Co--O--Co bond angles according to \textit{ab initio} calculations. At T=0.4~K, the magnetization M(B) exhibits step-like features that are also highly anisotropic. In the case of B∥b, a small hysteresis observed around the second field-induced magnetic transition (Bc2) indicates its first-order character, whereas divergence of the magnetic Gr\"uneisen parameter at Bc2 is suppressed upon cooling and signals the absence of quantum critical behavior upon entering the field-polarized state. None of our thermodynamic measurements provide evidence for a field-induced quantum spin liquid state near or above Bc2.
@article{arxiv.2603.03214,
title = {Anisotropic magnetoelastic coupling in the honeycomb magnet Na$_3$Co$_2$SbO$_6$},
author = {Prashanta K. Mukharjee and Sebastian Erdmann and Lichen Wang and Julian Kaiser and Anton Jesche and Pascal Puphal and Masahiko Isobe and Matthias Hepting and Bernhard Keimer and Philipp Gegenwart and Alexander A. Tsirlin},
journal= {arXiv preprint arXiv:2603.03214},
year = {2026}
}