Growth and Magnetooptical Properties of Anisotropic TbF3 Single Crystals

The present paper investigates the Faraday effect and absorption and luminescence spectra of single-crystal TbF3 measured at 90 K and 300 K. The optical-quality single-phase TbF3 crystals (structural type β-YF3) were grown by the Bridgman technique. Faraday rotation angles were measured at remagnetization along the [100] crystallographic axis. Low temperature optical measurements were carried out along the [100] axis. “Quasi-doublet” sublevels with energy at 0 cm-1, 65 cm-1 and 190 cm-1, and also a singlet sublevel with energy at 114 cm-1 located in the ground 7F6 multiplet were determined from the low temperature luminescence spectra. The Van-Vleck behavior of the magnetic susceptibility χb can be satisfactorily explained by the magnetic mixing of wave functions belonging to the ground and first excited “quasi-doublet” sublevels at 0 and 65 cm-1, respectively. Analysis of the oscillation dependences of the rotation angle showed that the value of the natural birefringence (Δn ≈ 0.0186) remains nearly constant within the wavelength and temperature ranges under investigation. As the temperature decreases, we find significant increases in the oscillation amplitude of the rotation angle and in the Verdet constant V. The spectral dependences V(χ) are linear throughout the temperature range. The magnetooptical activity of TbF3 can be explained by means of the spin- and parity-allowed electric-dipole 4f→5d transitions in the Tb3+ ions

Tb3+ Ion Optical and Magneto-Optical Properties in the Cubic Crystals KTb3F10

The optical and magneto-optical characteristics of KTb3F10 crystals in the transition region of 5D4 → 7F6 4f8 configurations of the Tb3+ ion at temperatures of 90 and 300 K were studied. The schemes of the optical transitions in the KTb3F10 crystals were constructed, and the energies of most of the Stark sublevels of the ground 7F6 and excited 5D4 multiplets of the Tb3+ ion split by the C4v symmetry crystal environment were determined. The presence of three- and two-doublet states in the energy spectra of the Tb3+ion multiplets 7F6 and 5D4, respectively, was established, which is in good agreement with theoretical predictions. The use of the wavefunctions of the Stark sublevels of multiplets split by a tetragonal crystal field and combining in the studied optical transition made it possible to explain some of the magnetic and magneto-optical features observed in the KTb3F10 single crystals

Some Interesting Features of the Tb3+ Magneooptics in teh Paramagnetic Garnets

The spectra of the absorption, luminescence, magnetic circular dichroism (MCD) and magnetic circular polarization of luminescence (MCPL) in the terbium–yttrium gallium garnet Tb3+:Y3Ga5O12 (Tb:YGG) have been studied within the visible and near ultraviolet (UV) spectral range for temperatures T = 85 and 300 K. The MCD spectrum observed within the UV absorption band for Tb:YGG is associated with spin- and parity-allowed electric-dipole 4f → 5d transitions occurring between levels of the ground 7F6 multiplet and the 7D state of the excited 4f(7)5d configuration of the Tb3+ ion. Analysis of the spectral and the temperature dependences of the magnetooptical and optical spectra has made it possible to identify magneto-optically-active 4f → 4f transitions occurring between Stark sublevels of the 5D4 and 7F5 multiplets in Tb3+:YGG. Quantum mechanical “mixing” of the three lowest energy Stark singlets in the excited 5D4 multiplet by an external magnetic field H leads to the change of the circularly polarized luminescence line intensities. The Zeeman effect in the UV absorption band 7F6 → 5L10 of Tb3+:YGG at T = 85 K was also studied. The magnetic field dependence of the Zeeman splitting of some absorption lines is found to exhibit unusual behavior: as the magnetic field increases, the band splitting decreases rather than increases. A parameterized Hamiltonian defined to operate within the entire 4f(8) ground electronic configuration of Tb3+ was used to model the experimental Stark levels, their irreducible representations (irreps.) and wave functions. The crystal-field parameters were determined using a Monte-Carlo method in which nine independent crystal-field parameters, were given random initial values and optimized using standard least-squares fitting between calculated and experimental levels. The final fitting standard deviation between 101 calculated and experimental Stark levels is 16.7 cm−1

Study of the Line Intensity in the Optical and Magnetooptical Spectra in Holmium-containing Paramagnetic Garnets

Studies of line intensity in the optical and magneto-optical spectra in the holmium-containing paramagnetic garnet Ho3+:YAG were carried out within the visible spectrum at T = 85 K. Detailed investigation of the magnetic circularly polarized luminescence spectra at 85 and 300 K on 5S2 → 5I8 emission transition in Ho3+:YAG was carried out. A quasi-doublet state in the energy spectrum of the Ho3+ ions was observed, characterized by a significant magneto-optical activity, which is caused by a large Zeeman splitting of the quasi-doublet. The measurement of the magnetic circular polarized luminescence spectrum carried out within one of the emission lines of the luminescence band 5S2 → 5I8 in Ho3+:YAG at 85 K shows significant magneto-optical effects of the intensity change of the emitted light, compared to that measured for the other emission lines in the same luminescent band

Analysis of the Optical and Magentooptical Spectra of Non-Kramers Pr3+(4f2) in Y_3A1_5O_12 Complemented by Crystal-Field Modeling

The spectra of the absorption, luminescence, magnetic circular dichroism (MCD) and magnetic circular polarization of luminescence (MCPL) in the praseodymium yttrium garnet aluminate Pr3+:YAG have been studied within the visible and near ultraviolet (UV) spectral range for temperature T=90 K and 300 K. Analysis of the spectral and the temperature dependences of the magnetooptical and optical spectra has made it possible to identify the optical 4f→4f transitions occurring between the Stark sublevels of the 1D2, 3P0 and 3H4 multiplets in Pr3+:YAG. It has been shown that for Pr3+:YAG in the MCD within the UV spectral range for the absorption bands due to allowed 4f→5d transitions, and also in the MCPL for the luminescence bands, respectively, due to forbidden 4f→4f transitions within the visible spectral range, a significant role is being played by the effect of quantum mechanical “mixing” of the states of the three lowest energy Stark singlets of the ground state 3H4 multiplet of the non-Kramers RE Pr3+ ion. A parameterized Hamiltonian defined to operate within the entire 4f2 ground electronic configuration of Pr3+ was used to model the experimental Stark levels, their irreducible representations (irreps) and wave functions. The crystal-field parameters were determined through use of a Monte-Carlo method in which nine independent crystal-field parameters, Bqk, were given random starting values and optimized using standard least-squares fitting between calculated and experimental levels. The final fitting standard deviation between 61 calculated to experimental Stark levels is 18 cm−1

Study of the Line Intensity in the Optical and Magnetooptical Spectra in Polmium-containing Paramagnetic Garnets

Studies of line intensity in the optical and magneto-optical spectra in the holmium-containing paramagnetic garnet Ho3+:YAG were carried out within the visible spectrum at T = 85 K. Detailed investigation of the magnetic circularly polarized luminescence spectra at 85 and 300 K on 5S2 → 5I8 emission transition in Ho3+:YAG was carried out. A quasi-doublet state in the energy spectrum of the Ho3+ ions was observed, characterized by a significant magneto-optical activity, which is caused by a large Zeeman splitting of the quasi-doublet. The measurement of the magnetic circular polarized luminescence spectrum carried out within one of the emission lines of the luminescence band 5S2 → 5I8 in Ho3+:YAG at 85 K shows significant magneto-optical effects of the intensity change of the emitted light, compared to that measured for the other emission lines in the same luminescent band

Optical and Magnetooptical Properties of Terbium–Scandium–Aluminum and Terbium-Containing (Gallates and Aluminates) Garnets

Comparative measurements of the Faraday rotation in Tb3Ga5O12 (TGG) and Tb3Sc2–xAl3+хO12 (TSAG) garnets shows the values of the Verdet constant for TSAG are about 25% higher than that of TGG in the wavelength range 400–700 nm at the temperatures T=95 and 300K. The increase of the Verdet constant is explained by increase of the “paramagnetic” frequency factor caused by the shift of the resonance frequency of the first allowed 4f→5d transition to the area of the lower frequencies in UV. The shift and observed strong broadening of the UV absorption bands in TSAG are explained by significant modification of the crystalline environment of the Tb3+ ion in this garnet. A comparison of the data of the C/D ratio in TSAG with the value of the magnetic moment of the Tb3+ ground state in Tb3Al5O12 (TAG) determined from magnetic measurements, showed an acceptable agreement for these parameters measured by fundamentally different methods. Measurements of the visible emission spectra reveal a strong influence of some disordering of the crystal field (CF) in TSAG in comparison with the terbium–aluminum garnet spectra. Magneto optica leffects of the intensity change of the luminescence lines in TSAG is caused by modification of the electronic structure of the 5D4 and 7F5 multiplets by Sc3+ ions in the lattice, leading to a local symmetry reduction of the Tb3+ ion in TSAG