Anisotropic magnetoelastic coupling in the honeycomb magnet Na 3 Co 2 SbO 6

This is the authors' abstract. We don't add key points for this paper.

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 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 Grüneisen 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.