TB OXIDATION-STATE AND HYBRIDIZATION IN Y0.9TB0.1BA2CU3O7-DELTA(DELTA=0.02, 0.84) - A MAGNETIC-SUSCEPTIBILITY AND X-RAY-ABSORPTION STUDY

A variety of experimental techniques are employed to probe the electro nic state of Tb in the supeconductor Y0.9Tb0.1Ba2Cu3O7-delta. An analy sis of neutron-diffraction data reveals that Tb is incorporated into t he sample, replacing Y. There are no anomalies observed in the lattice constants or the planar oxygen thermal parameters determined from the neutron data, but the low concentration of Tb prohibits the determina tion of Tb oxidation state from these data alone. A comparison of expe rimentally determined magnetic susceptibilities with those calculated from single-ion, crystal-field models assuming either Tb3+ or Tb4+ sho ws a close agreement between the Tb3+ model and experiment. The presen ce of Tb3+ is confirmed by x-ray absorption near-edge spectroscopy. L3 -edge data are used to argue that the Tb ions are not significantly hy bridized in Y0.9Tb0.1Ba2Cu3O7-delta.