K2Co2TeO6 : A layered magnet with a S=12Co2+ honeycomb lattice

Recent observations of Kitaev interactions in d7 electron configurations have generated research interest in Co2+ based honeycomb magnets. Here, we report the synthesis of a K2Co2TeO6 single crystal. X-ray diffraction and electron microscopy experiments show that K2Co2TeO6 crystallizes in a $P$63/$mcm$ space group with undistorted honeycomb layers of Co2+ ions. Anisotropic magnetic and thermodynamic characterizations demonstrate an effective S = $\frac{1}{2}$ state of Co2+ at low temperature, competing magnetic phases, and weak magnetic transitions that can be suppressed by applying fields. Moreover, the interlayer K disorder level is tunable by thermal treatments, and it affects the magnetic features obviously. In conclusion, our findings provide a new and promising platform for studying Kitaev physics.