Structure and magnetism of a new hexagonal polymorph of Ba3Tb(BO3)3 with a quasi-2D triangular lattice

Abstract

This article reports the structural and magnetic characterisation of a new hexagonal ( P 6 3 c m ) low-temperature phase of Ba3Tb(BO3)3, isostructural with the heavier lanthanide borates with formula Ba3 Ln(BO3)3 (Ln ​= ​Dy–Lu). The crystal structure contains a quasi-two-dimensional (2D) triangular lattice of Tb3+ ions and is predicted to display unusual magnetic behaviour as a result of the low dimensionality. Magnetic susceptibility χ ( T ) shows antiferromagnetic interactions ( θ C W = − 7.15 K) and no sharp ordering transition at T ≥ 2 K, but analysis of χ ’ ( T ) , isothermal magnetisation and heat capacity suggests the possibility of short-range ordering at T ≈ 10 K. The material exhibits an inverse magnetocaloric effect at T < 4 K.