Magnetoresonance investigation of low-dimensional magnet NaFe(WO4)2

The low-dimensional monoclinic compound NaFe(WO4)2 was investigated by resonance methods in the frequency region from 25 to 142 GHz, at temperatures ranged from 1,8 to 300 K. The EPR investigation near the phase transition suggests a two-dimensionality of the NaFe(WO4)2 magnetic structure. The frequency-field dependences of the AFMR spectrum studied in the ordered phase shows that this compound belongs to biaxial antiferromagnets. The characteristic parameters of the AFMR energy spectrum were calculated and the following values were obtained: energy gaps ν1 = 141 GHz, ν2 = 168,7 GHz, anisotropy fields Ha1 = 10,5 kOe, Ha2 = 15 kOe and exchange field He = 121 kOe. The relation between intra- and inter-plane exchange was estimated. An additional absorption, connected with local modes caused by the disturbance of the magnetic structure translation order was detected