OBSERVATIONS OF LONG-PERIOD STRUCTURES ASSOCIATED WITH CHARGE ORDERING IN BI0.2CA0.8MNO3

Long-period structures with 32- and 36-fold periodicity to the origina l unit lattice distance were observed in a perovskite manganese oxide Bi0.2Ca0.8MnO3 at around 130 K, in addition to the one with fourfold p eriodicity. Quantitative electron diffraction profiles were measured f or the long-period structure, where the intensity of superlattice refl ections was observed to increase with increasing scattering angle due to static strain. This result gave a reasonable explanation for occurr ence of the charge ordering of Mn3+ and Mn4+ ions, which was responsib le for the creation of the long-period structures in Bi0.2Ca0.8MnO3.