Magnetic and thermal properties of single-crystal NdFe3(BO3)4

The neodymium ferroborate NdFe3(BO3)(4) undergoes an antiferromagnetic transition at T-N = 30 K, which manifests itself as a lambda-type anomaly in the temperature dependence of the specific heat C and as inflection points in the temperature dependences of the magnetic susceptibility chi measured at various directions of an applied magnetic field with respect to the crystallographic axes of the sample. Magnetic ordering occurs only in the subsystem of Fe3+ stop ions, whereas the subsystem of Nd3+ stop ions remains polarized by the magnetic field of the iron subsystem. A change in the population of the levels of the ground Kramers doublet of neodymium ions manifests itself as Schottky-type anomalies in the C(T) and chi(T) dependences at low temperatures. At low temperatures, the magnetic properties of single-crystal NdFe3(BO3)(4) are substantially anisotropic, which is determined by the anisotropic contribution of the rare-earth subsystem to the magnetization. The experimental data obtained are used to propose a model for the magnetic structure of NdFe3(BO3)(4).