College Park, Maryland      June 6 - 10 , 2004

T3-A1 (3:45 PM): Charge, orbital and spin ordering in RBaFe2O5+x perovskites (Invited)

P. M. Woodward (Department of Chemistry, Ohio State University), P. Karen (Department of Chemistry, University of Oslo)

Transition-metal oxides adopting the perovskite structure (or closely related structure types) are well known for their interesting electronic properties (i.e. High TC superconductivity, colossal magnetoresistance, charge disproportionation, etc.). The oxygen-deficient double perovskites RBaFe2O5+x (R = Nd, Sm, Tb, Ho, Y) are among the more interesting classes of perovskite related compounds. When x = 0 these compounds contain square-pyramidal iron with an average valence of +2.5. By changing temperature all three Robin-Day classes of iron mixed-valence can be observed. In the high temperature paramagnetic state all iron atoms are equivalent. Upon cooling antiferromagnetism sets in, followed by a two-step charge-localization process. The localization of the conduction electrons triggers phenomena such as charge and orbital ordering, reorientation of the antiferromagnetic structure and in some cases induced magnetism of the rare-earth sublattice. Variable temperature high-resolution synchrotron x-ray and neutron powder diffraction measurements, neutron thermodiffractometry, transport and magnetic susceptibility measurements are used to characterize the behavior of this interesting family of compounds.

Back to the Program

Last modified 14-May-2004 by website owner: NCNR (attn: Bill Kamitakahara)