Coherent intergrowth of simple cubic and quintuple tetragonal perovskites in the system Nd2-ε Ba3+ε (Fe, Co)5 O15-δ
Résumé
Abstract Investigation of the Nd2-ε Ba3+ε (Fe,Co)5 O15-δ system, combining X-ray diffraction and electron microscopy, has allowed a tetragonal quintuple ordered perovskite "ap ×ap ×5ap " phasoid inter-grown within a single cubic perovskite matrix to be evidenced for ε=0. This nanoscale chemically twinned perovskite is compared with other members, Ln=Sm, Eu, Pr. The unusual long range ordering of the layers develops strains due to size mismatch between Ba2+ and Ln3+ cations. Importantly, two factors allow the strains to be decreased (i) special intergrowths of double (LnBaFe2 O6-δ ) and triple (LnBa2 Fe3 O9-δ ) perovskite ribbons/layers oriented at 90°, (ii) nanoscale chemical twinning. The spin locking effect of the nano-domain boundaries upon the magnetic properties of these perovskites is discussed. © 2015 Elsevier Inc.