A SYNCHROTRON X-RAY STUDY OF THE ELECTRON-DENSITY IN C-TYPE RARE-EARTH-OXIDES

Structure factors for small synthetic crystals of C-type sesquioxides Y2O3, the rare earth (RE) Dy2O3 and Ho2O3 were measured with focused l ambda = 0.7000(2) Angstrom synchrotron X-radiation, and for Ho2O3 were re-measured with an MoK alpha (lambda = 0.71073 Angstrom) source. App roximate symmetry in the deformation electron density (Delta rho) arou nd a RE atom with pseudo-octahedral O coordination matches the cation geometry. Interactions between heavy metal atoms have a pronounced eff ect on the Delta rho map. The electron-density symmetry around a secon d RE atom is also perturbed significantly by cation-anion interactions . The compounds' magnetic properties reflect this complexity. Space gr oup Ia (3) over bar, cubic, Z = 16, T = 225 K: Y2O3, Mr = 225.82, a = 10.5981(7) Angstrom, V = 1190.4 (2) Angstrom(3), D-x = 5.040 Mg m(-3), mu(0.7) = 37.01 mm(-1) F(000) = 1632, R = 0.067, wR = 0.067, S = 9.0( 2) for 1098 unique reflections; Dy2O3, M(r) = 373.00, a = 10.6706 (7) Angstrom, V = 1215.0(2) Angstrom(3), D-x = 8.156 Mg m(-3), mu(0.7) = 4 4.84 mm(-1), F(000) = 2496, R = 0.056, wR = 0.051, S = 7.5(2) for 1113 unique reflections; Ho2O3, M(r) = 377.86, a = 10.606 (2) Angstrom, V = 1193.0(7) Angstrom(3), D-x = 8.415 Mg m(-3), mu(0.7) = 48.51 mm(-1), F(000) = 2528, R = 0.072, wR = 0.045, S = 9.2(2) for 1098 unique refl ections of the synchrotron data set.