K2Co2TeO6: A layered magnet with a S=21 Co2+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 P63/mcm space group with undistorted honeycomb layers of Co2+ ions. Anisotropic magnetic and thermodynamic characterizations demonstrate an effective S = 12 state of Co2+ at low temperature, competing magnetic phases, and weak magnetic transitions that can be suppressed by applying fields. The interlayer K disorder level is found to be tunable by thermal treatments, and it plays detectable effects on magnetic behaviors. Our discoveries offer a promising platform for exploring intricate frustrated magnetism, intertwined structural orderings, and Kitaev interactions.