Crystal growth and magnetic properties of hexagonal Ba4CuNb3O12 single crystals

Abstract

We report a systematic investigation of the growth of high-quality hexagonal perovskite Ba₄CuNb₃O₁₂ single crystals using the flux method. The optimal growth involved using the tetragonal phase BaCu_0.33Nb_0.67O₃ as the precursor, with 20 g CuO as the flux, a cooling rate of 1 °C h⁻¹ between 1350 °C and 1100 °C, and a cooling rate of 2 °C h⁻¹ from 1100 °C to 930 °C. The magnetic properties along the ab-plane and the perpendicular direction are thoroughly studied. Fitting the inverse magnetic susceptibility data from 2 K to 300 K with the modified Curie–Weiss (CW) law yields a Weiss temperature (θ_CW) of −1.14 K, indicating the presence of antiferromagnetic correlations in the ground state between Cu²⁺ ions via superexchange interactions. Furthermore, the specific heat data of Ba₄CuNb₃O₁₂ align well with the Debye–Einstein phonon model, allowing us to estimate the Debye temperature of 199 K and the average phonon velocity of 2014.98 m s⁻¹.