Spin-state ordered clusters in the perovskite NdBaCo2O5.47 -: art. no. 184421

NdBaCo2O5.47 cobaltite has been investigated using neutron and synchrotron powder diffraction. At T(MI)similar to360 K, the compound exhibits an associated metal-insulator and spin-state transition commonly observed in these systems. At T(N)similar to275 K, the IS-Co3+ species order in a AFM G-type structure. At T(SSO)similar to230 K, the AFM G-type volume fraction is gradually transformed into spin-state ordered clusters having a distinct magnetic structure. These clusters result from a selective IS-Co3+ (t(2g)(5)e(g)(1)) to LS-Co-III (t(2g)(6)e(g)(0)) crossover and the ordering of the diamagnetic ions over similar to350 Angstrom correlation lengths. The same electronic phase segregation is observed in TbBaCo2O5.46 and seems to occur only for a narrow range of oxygen stoichiometry.