Nd 3+ scrystal-field transitions studied by Raman and FIR spectroscopies in Nd 2 BaZnO 5 s

We have investigated the crystal-field levels of the lowest multiplets of ${\mathrm{Nd}}^{3+}$ in the ${\mathrm{Nd}}_{2}$ ${\mathrm{BaZnO}}_{5}$ compound. Raman scattering arising from the excitation of the ground-state level to several ${\mathrm{I}}_{9\mathrm{/}2}$ , ${\mathrm{I}}_{11\mathrm{/}2}$ , and ${\mathrm{I}}_{13\mathrm{/}2}$ levels has been observed as a function of the temperature. Fourier-transform infrared reflectivity (between 30 and 7000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ ) has been measured down to 30 K. Bands corresponding to transitions from ${\mathrm{I}}_{9\mathrm{/}2}$ to ${\mathrm{I}}_{11\mathrm{/}2}$ , ${\mathrm{I}}_{13\mathrm{/}2}$ , and ${\mathrm{I}}_{15\mathrm{/}2}$ multiplets were obtained and are in very good agreement with the observed Raman crystal-field transitions (CFT). The first excited state at 65 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ becomes detectable in Raman scattering as the temperature decreases, i.e., as its thermal population decreases. It is also observed that the intensity of IR absorption peaks from this level decreases with temperature, as expected, but some are still detectable, even at 30 K. The width of the 65 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ Raman peak is larger than all other observed Raman CFT in this compound. This width is due to its proximity to the ground state, i.e., to the high probability of relaxation. A small component of inhomogeneous broadening due to slight differences in Nd environments is also present. The possible coupling between this CFT and a near phonon is discussed.