Changes of the local magnetic properties of the optically excited Nd3+ ions and their manifestation in the near IR spectra of the Nd0.5Gd0.5Fe3(BO3)4 crystal

Abstract Polarized absorption spectra of f – f transitions 4 I 9/2 → 4 F 3/2 and ( 2 H 9/2 + 4 F 5/2 ) in the Nd 3+ ion in the Nd 0.5 Gd 0.5 Fe 3 (BO 3 ) 4 single crystal were studied as a function of temperature in the range of 2–40 K and as a function of magnetic field in the range of 0–65 kOe at 2 K. It was found out that the selection rules for f – f electron transitions substantially changed in the magnetically ordered state of the crystal, and they strongly depended on the orientation of the Fe and Nd ions magnetic moments relative to the light polarization. The splitting of the ground and excited states of the Nd 3+ ion in the exchange field of the Fe sublattice were determined. It was revealed that the value of the exchange splitting (the exchange interaction) in the excited states did not correlate with the theoretical Lande factors. The Lande factors of the excited states were experimentally found. In general, the local magnetic properties in the vicinity of the excited ion depend substantially on its electron state. In particular: (1) in one of the excited states a weak ferromagnetic moment appears, (2) the changes of type of the local magnetic anisotropy take place in some excited states, and (3) in some excited states the energetically favorable orientation of the Nd 3+ ion magnetic moment is opposite to that in the ground state. In some excited states the nonequivalent Nd 3+ centers were found out.