Local Disorder in Ln(2)Ti(2)O(7) (Ln = Gd, Tb, Dy) Pyrochlores

The temperature dependences of extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectra of Ln(2)Ti(2)O(7) (Ln = Gd, Tb, Dy) geometrically frustrated magnets with a pyrochlore structure are presented. The temperature dependences of the Ln-O and Ti-O interatomic bond lengths and Debye-Waller factors sigma(2) characterizing the local static and dynamic disordering of bonds have been obtained in the temperature range of 10-300 K. The stiffnesses of metal-oxygen bonds and the parameters of local disordering of the structure have been determined from the dependences sigma(2)(T). The effect of the magnetic state of rare-earth ions on local features of the Ln(2)Ti(2)O(7) structure has been described. The characteristics of local disorder in pyrochlores under study have been compared to dysprosium zirconate Dy2Zr2O7 having a disordered fluorite structure.