Oxygen-deficient effect on charge ordering in spin- and charge-frustrated ferrite YFe₂ O₄-δ

The effects of oxygen deficiency on charge ordering were investigated by transmission electron microscopy at various deficiencies and temperatures of YFe₂ O₄-δ. We found that the detailed nature of the charge ordering structures is associated with changes in the superlattice reflections and diffuse scattering. They go from (1/3 1/3 1/2)-type superlattice reflection to (1/3 1/3 l) -type straight-type diffuse scattering, then to zigzag-type diffuse scattering. With the oxygen deficiencies increased, the interchange correlation of Fe-O bilayers obviously decreases, yet the triple superperiodicity along [110] remains unchanged. These findings on frustrated ferrites indicate the stability of in-plane threefold charge ordering and the importance of the interchange interaction between bilayers in the structural phase transitions.