Ferrimagnetism and anisotropic phase tunability by magnetic fields in Na2Co2TeO6

Na2Co2TeO6 is a honeycomb-lattice compound with a zigzag antiferromagnetic order [1,2]. It has recently been proposed to be a Kitaev-like magnet based on high-spin d7 electron configuration [3,4]. To assess how close it is to realizing Kitaev quantum spin liquids, we have measured magnetization and specific heat on high-quality single crystals in magnetic fields applied along high-symmetry directions [5]. With small training fields, we find a canonical ferrimagnetic behavior below 27 K, which reveals additional Neel-type order of canted moments. Moreover, moderate fields in the honeycomb plane can suppress the thermal transition at 27 K, and seem to partly reverse the moment-canting when applied perpendicular to the zigzag chains. In contrast, out-of-plane fields leave the transition largely unaffected, but promotes another transition below 10 K, possibly also related to canting reversal. Our study indicates the magnetism of Na2Co2TeO6 is highly anisotropic and close to tipping points between competing phases.

[1] Lefrancois et al., Phys. Rev. B 94, 214416 (2016).
[2] Bera et al., Phys. Rev. B 95, 094424 (2017).
[3] Liu et al., Phys. Rev. B 97, 014407 (2018).
[4] Sano et al., Phys. Rev. B 97, 014408 (2018).
[5] Yao et al., arXiv:1908.09427.