Analysis of the optical spectra and paramagnetic susceptibility of DyOF

The optical absorption spectra of the rhombohedral DyOF were measured at selected temperatures between 9 and 300 K. The emission spectra of the Dy3+ ion in the LaOF and GdOF matrices were obtained at 77 K and room temperature. The energy level scheme of Dy3+ (4P(9) electron configuration) was simulated with a Hamiltonian of 20 parameters. The diagonalization of the energy matrices including simultaneously the free ion and crystal field (c.f.) interactions was carried out for the C-3v point symmetry of the RE(3+) site. Good correlation with an rms deviation of 17 cm(-1) was obtained between the experimental and calculated energy level schemes of 153 Kramers doublets. The c.f. parameters show only slight distortion from Oh symmetry. A comparison to Pr3+ (4f(2)), Nd3+ (4f(3)), Sm3+ (4f(5)), EU(3+) (4f(6)) and Tb3+ (4f(8) electron configuration) in other REOF matrices showed smooth evolution of the c.f. effect which was discussed in terms of the possible interactions involved. The x-ray powder diffraction pattern of DyOF between 6.5 degrees < 2 theta < 120 degrees was analysed by the Rietveld profile refinement method. The structural data were used to calculate the c.f. parameters by the modified electrostatic point charge model yielding B-0(4), B-3(4) and B-0(6) values close to the experimental ones, whereas the B-0(2), B-3(6), and B-6(6) values were too large. Using the experimental free ion and c.f. wave functions, the paramagnetic susceptibility of DyOF as a function of temperature was simulated. Above the Neel temperature (3.6 K), good agreement was obtained between the calculated and experimental susceptibilities in the paramagnetic range.