Vibrational properties of Nd3+, Eu3+, Er3+ and Ho3+ doped KGd(WO4)2 single crystals studied by Raman scattering method

The polarized Raman spectra of KGd(WO4)(2) single crystals doped with rare earth ions Nd3+, Eu3+, Ho3+ and Er3+ were carried out in the range of internal and external vibrations 20 - 1000 cm(-1) at room temperature. No significant influence of rare earth ions doping on the band positions was observed. However, most of detected in y(xx)z and y(xy)z scattering geometry Raman bands exhibit depolarization. The highest depolarization ratio is observed for the bands at 526, 684 and 766 cm(-1) assigned to the stretching vibrations of the WOOW oxygen bridge bonds. While, the bands at 348, 371 and 899 cm(-1) assigned to the bending and stretching vibrations of WO42- tetrahedra, are almost fully polarized for all investigated crystals. The depolarization of bands is due to distortion of WO42- tetrahedra and WOOW bridge bonds forming the structure of KGd(WO4)(2). Moreover, the lowest degree of depolarization for analyzed bands was observed for KGd(WO4)(2) : Nd crystals, which exhibits less affected vibrational spectra by doping ions than other investigated crystals.