Features of the intensity behavior of Kramers doublet components in NdFe3(BO3)(4) in the transverse Zeeman geometry

Nontrivial magnetic field dependence of the polarization of the Kramers doublet absorption lines (15 971–15 978 cm⁻¹) was observed in the range of the ⁴I_9/2 → ²H_11/2 optical transition of Nd³⁺ ion in an easy-plane antiferromagnet NdFe₃(BO₃)₄ in the transversal Zeeman effect geometry. Values of the transversal g factor and the effective exchange field with Fe³⁺ magnetic subsystem were determined for the excited state of Nd³⁺ from the field dependence of the doublet splitting. A semiempirical equation was proposed for the description of the field dependence of the intensities of the polarized components of the absorption lines corresponding to the Kramers doublet 15 971–15 978 cm⁻¹. Besides the scaling factors, the equation contains only the independently determined magnitudes of exchange fields for the ground and excited states as parameters.