Magnetic properties of TbFe3(BO3)4

Magnetization curves and temperature dependences of initial magnetic susceptibility of single-crystalline TbFe3(BO3)4 are measured both along and perpendicular to the trigonal c-axis from 2 to 350 K. For T<T N=40 K, the spin-flop transition with small hysteresis and temperature-dependent magnetization jump is observed for H||c. The H-T phase diagram is constructed. The highly anisotropic character of magnetic susceptibility is ascribed mainly to the Ising behavior of the Tb3+ ion in the trigonal crystal field. The specific heat, measured up to 3 T at H||c, is characterized by Schottky anomalies around 20 and 150 K associated with the change of occupation of excited energy levels of the Tb3+ ion being split by f-d coupling and crystal field. All the properties and effects observed are described in the context of the unified approach, which is based on the mean-field approximation and crystal-field calculations. The main parameters of the compound are determined