Thermodynamics of a frustrated quantum magnet on a square lattice

We report the magnetic and calorimetric measurements in single crystal samples of the square lattice J₁ - J₂ quantum antiferromagnet BaCdVO(PO₄)₂ [1]. An investigation of the scaling of magnetization reveals a “dimensionality reduction” indicative of a strong degree of geometric frustration. Below a characteristic temperature less than 150 mK we observe the emergence of a new strongly fluctuating quantum phase close to full magnetic saturation. It is separated from the magnetically ordered state by 1-st and 2-nd order phase transitions, depending on the orientation of the applied magnetic field. We suggest that the new phase may indeed be the theoretically predicted spin nematic state.

[1] K. Yu. Povarov, V. K. Bhartiya et al. arXive:1807.09549v1 (2018).