Linear high-field magnetoelectric coupling and ferroelectric order in a proposed Kitaev compound: Na2Co2TeO6:

We studied the ferroelectric (FE) order associated with a linear magnetoelectric coupling in kitaev compound Na2Co2TeO6. The ferroelectric order around ∼72 K (TFE), much above the antiferromagnetic ordering (TN) at 26 K, is confirmed by the pyroelectric and bias-electric field measurement. A reasonable value of the electrocaloric effect is observed around TFE. The magnetic entropy change (ΔSM) emerges at the onset of FE order, exhibits a maximum of around 35 K, which is also much higher than TN, pointing towards a dominant short-range ordering above TN. A structural transition is proposed to a polar P63 structure at TFE from a high-temperature P6322 space group, which accounts for the emergence of polar order. The distortion of the CoO6 octahedral and the layered honeycomb structure around TFE and TN has been discussed to correlate the significance of the magnetic frustration, the occurrence of FE order, the multi-caloric effect, and the feasible Kitaev spin liquid state. The multifunctional properties of the compound have drawn special attention and are of fundamental interest.