Displacive Disorder, Anti-site Disorder and Magnetic Properties of Cubic Pyrochlores Bi2MM´O7 with M = Sc, Cr, Mn and Fe and M´ = Nb Ta and Sb

BLANCO, M.C; JALIT, Y.; FRABCO, DIEGO G.; PANNUNZIO MINER, E.V.; PAESANO JR., A.; NIEVA, G.; CARBONIO, R.E.

PHYSICA B - CONDENSED MATTER

ELSEVIER SCIENCE BV

Año: 2011

0921-4526

The samples Bi2BB0O7, with B¼Cr and Fe and B0¼Nb, Ta and Sb were prepared by solid state method. The crystallographic structure was investigated on the basis of X-ray powder diffraction data. Rietveld refinements show that the crystal structure is cubic, space group Fd-3m. The Bi3þ cation on the eight- coordinate pyrochlore A-site shows displacive disorder, as a consequence of its lone pair electron configuration. There is also a considerable A-site disorder shown by Rietveld Analysis and confirmed in the case of the iron containing samples with M¨ ossbauer spectroscopy. The magnetic measurements show paramagnetic behavior at all temperatures for the Cr oxides. The Fe pyrochlores show antiferro- magnetic order around 10 K.