Lightly stuffed pyrochlore structure of single-crystalline Yb 2 Ti 2 O 7 grown by the optical floating zone technique

摘要: Recent neutron scattering and specific heat studies on the pyrochlore Yb2Ti2O7 have revealed variations in its magnetic behavior below 265mK. In best samples, a sharp anomaly is observed at T=265mK. Other especially single crystals, broad features which vary sharpness temperature depending sample, indicating that ground state may be qualitatively different such samples. We performed detailed comparisons of chemical structure pulverised crystal Yb2Ti2O7, grown by floating zone technique, to sintered powder sample Yb2Ti2O7. Rietveld refinements diffraction data these samples reveal crushed described as "stuffed" pyrochlore, Yb2(Ti(2-x)Yb(x))O7-(x/2) with x = 0.046(4), despite perfectly stoichiometric starting material. Substituting Yb3+ non-magnetic Ti4+ sublattice would introduce random exchange bonds local lattice deformations. These are expected mechanism leading variation delicate Determination cubic cell length, a, could useful method for characterizing stoichiometry non- crystals room temperature.