Nano-sized domains related to dielectric anomaly in YFe₂O _4-δ

We examined microstructures related to the charge ordering in YFe ₂O_4-δ, by transmission electron microscopy. It is found that two types of characteristic diffuse scatterings appear at room temperature. One is characteristic diffuse streaks elongated along the [0001] direction through the (1/3 1/3 2/3 0)-type reciprocal positions and the other is diffuse spots at (1/3 - η 1/3 - η 2/3 + 2 η 0)-type incommensurate positions (η ≈ 0.066). Real-space images revealed that the former diffuse scattering is related to nano-domains due to the charge ordering and the latter one is related to those due to vacancy ordering. The presence of the nano-sized domains should be strongly related to the dielectric anomalies found in YFe₂O_4-δ.