Antiferromagnetic resonance in ferroborate NdFe3(BO3)4

The AFMR spectra of the NdFe3(BO3)4 crystal are measured in a wide range of frequencies and temperatures. It is found that by the type of its magnetic anisotropy the compound is an “easy-plane” antiferromagnet with a weak anisotropy in the basal plane. The effective magnetic parameters are determined: anisotropy fields Ha1=1.14 kOe and Ha2=60 kOe and magnetic excitation gaps Δν1Δν1=101.9 GHz and Δν2Δν2=23.8 GHz. It is shown that commensurate–incommensurate phase transition causes a shift in resonance field and a considerable change in absorption line width.At temperatures below 4.2 K nonlinear regimes of AFMR excitation at low microwave power levels are observed.