X-RAY PHOTOELECTRON-SPECTRA OF LANTHANIDE ORTHONIOBATES LNNBO(4)

A new series of ferroelectrics, orthoniobates LnNbO(4), where Ln = lan thanide (except for Pm and Tm), are studied by X-ray photoelectron spe ctroscopy over the electron binding energy range from 0 to 1350 eV. Th e dependence of the relative intensity of the Ln 4f electron line on t he atomic number of the lanthanide Z is established. It is shown that the fine structure in the electron binding energy region from 15 to 50 eV is mainly due to the electrons of the inner valence molecular orbi tals. The intensity of the shake-up satellites in the spectra of elect rons from various subshells of the lanthanide ion decreases with decre ase in their binding energy. The splitting parameters for the Ln 5s, 4 s electron lines connected with the multiplet splitting are determined , as well as the parameters of the fine structure of the spectra of th e Ln 4p electrons arising from the dynamic effect. The dependence of t he width of the Nb 4s electron line on the number it of the unpaired L n 4f(n) electrons is established which is presumably due to the indire ct exchange interaction between the lanthanide and niobium ions via ox ygen.