Magnetic properties and phase diagram of quasi-two-dimensional Na2Co2TeO6single crystal under high magnetic field.

We investigated the magnetic characteristics of Na2Co2TeO6at different temperatures and magnetic field. The experimental results indicated that the magnetic field can disturb the antiferromagnetic interaction and lead to the disorder. Magnetization curves measured with different anglesθ(θis between the magnetic field direction andcaxis) express the magnetocrystalline anisotropy in this system. When the angleθ= 0 (magnetic field parallel tocaxis), two continuous magnetic phase transitions at critical temperatureTN1andTN3were observed. Asθchanges,TN1is almost independent onθ, indicating the magnetic ordering atTN1was a spontaneous behavior with a robust AFM characteristic. On the other hand, asθincreases from 0 to 180,TN3presents extreme value atθ= 90 (magnetic field perpendicular tocaxis). It indicates thatTN3were sensitive to temperature and magnetic fields. At some angles closing toabplane, an additional phase transition was observed atTN2.This phase transition atTN2may mainly result from the long range antiferromagnetic ordering withinab-plane. Furthermore, the magnetization measurement up to 50 T revealed the strong antiferromagnetic coupling in the system, and in which the magnetic coupling within the honeycomb layers is strong and the magnetic coupling interaction between honeycomb layers is weaker. Based on the experimental results, we have obtained the complete magnetic phase diagram.