NEUTRON-SCATTERING STUDIES OF YB-BEARING SILICATE-GLASSES

The static and dynamic magnetic response of the Yb3+ ions in 3Na2O.Yb2 O3.6SiO2 glass and the isochemical crystalline silicate Na3YbSi3O9 has been studied by neutron diffraction, inelastic magnetic scattering, a nd magnetic susceptibility measurements. The rare earth sites in the g lass have an average coordination number of 5.6 +/- 0.5 and give a mea n rare earth-oxygen bond length of 2.23 angstrom; average Si-O and O-O coordination numbers and bond distances are comparable to those in vi treous SiO2. The magnetic excitation spectrum of the Na3YbSi3O9 materi al was analyzed by a crystal field model using a method of descending symmetry. The magnetic susceptibility and the excitation spectrum of t he Yb glasses can be described by a distribution of ligand field effec ts on the Yb3+ ions that are similar to the nominal crystal field in c rystalline Na3YbSi3O9.