Optical and magneto-optical properties of Nd0.5Gd0.5Fe3(BO3)4 single crystal in the near IR spectral region

Polarized optical absorption and magnetic circular dichroism (MCD) spectra of the trigonal multiferroic Nd0.5Gd0.5Fe3(BO3)4 were studied in the region of transitions 4I9/2 → 4F3/2 and 4I9/2 → (4F5/2 + 2H9/2) in Nd3+ ion. Components of the crystal field splitting of the states were identified with the help of MCD and polarized absorption spectra. Splitting of the Nd3+ absorption lines caused by the magnetic ordering were observed. Splitting of Nd3+ ground state in Fe-sublattice exchange field was found to be ∼9 cm−1 at 5.7 K. The Zeeman splitting of some absorption lines in the external magnetic field and changes of the effective Landé factors in the C3-direction as a result of the corresponding optical transitions were found. Peculiarities in the temperature behavior of the absorption lines connected both with the ground and excited states were revealed. Peculiarities connected with the excited states testify to the local crystal distortions in the excited states.

► Absorption spectra of Nd3+ in Nd0.5Gd0.5Fe3(BO3)4 were studied down to 5.7 K.
► The Zeeman splitting of lines were found from magnetic circular dichroism spectra.
► Exchange splitting of absorption lines were observed and measured.
► Crystal field states were identified.
► Local distortions in some excited states were revealed.