Structural modulation and spin glassiness upon oxidation in oxygen storage material <i>Ln</i>FeMnO4+x for <i>Ln</i> = Y, Lu, and Yb

The mixed valence multiferroic LnFe2+Fe3+O4 (where Ln = Y, Lu, and Yb) can reversibly uptake oxygen into its lattice, which is evidenced by a crystallographic phase transition along with the appearance of structural modulations. In this study, we show that Mn-substituted version also be readily oxidized to LnFe3+Mn3+O4.5 revealing similar storage behavior. Through neutron, electron, synchrotron x-ray diffraction studies, observe modulation attribute displacement wave in fully compound. This exhibits commensurability wavevector q (−2/7, 1/7, 0). Bond summation analysis plausible interstitial positions suggests insertion likely occurs at middle Fe/Mn–O bipyramid layers. LnFeMnO4.5 two-dimensional, propagates ab-plane, highly symmetric as 12 identical vectors are observed patterns. nature lanthanide, Ln3+, does not seem influence such modulations since satellite reflections for all three samples Yb. Both LnFeMnO4 display spin glassy behavior 2D short-range magnetic ordering being LnFeMnO4. Analysis neutron data reveals correlation length ∼10 nm. Upon oxidation LnFeMnO4.5, order significantly suppressed.