Thermodynamic and optical properties of NdCr3(BO3)4

We present magnetization and specific heat data as well as optical spectra of NdCr3(BO3)(4) single crystals. At T-N=8 K, the magnetic and specific heat data imply long-range antiferromagnetic spin order of the Cr3+ subsystem. This observation is corroborated by the spectroscopic studies since in the ordered state the Nd3+ Kramers doublets are split by the internal staggered magnetic field. The splitting is also visible in a Schottky anomaly at the specific heat. In the spin-ordered phase, we find a staggered magnetic field at the Nd sites of 35 kG at 1.8 K. The values lambda(Nd-Cr)=3.9 kG/mu(B) and lambda(Cr-Cr)=29.4 kG/mu(B) are obtained for the molecular-field constants of the Nd-Cr and the Cr-Cr interactions, respectively. The analysis of the magnetic susceptibility data points to the easy-plane type of the antiferromagnetic order. Several experimental manifestations of the low dimensionality of the title compound are mentioned.