Antiferromagnetic resonance in ferroborate NdFe sub(3)(BO sub(3)) sub(4)

The AFMR spectra of the NdFe sub(3)(BO sub(3)) sub(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 H sub(a)1=1.14 kOe and H sub(a)2=60 kOe and magnetic excitation gaps Delta [nu] sub(1)=101.9 GHz and Delta [nu] sub(2)=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.