Magnetic Clustering and Possible Chemical Nonuniformity in Bi0.125Ca0.875MnO3

The manganite system Bi1-xCaxMnO3 possesses intriguing properties in the low bismuth doping region. In this electron doped region (0.6$<$x$<$1), a large ferromagnetic (FM) moment of $\sim $1.2 Bohr magnetons per Mn site is found for x$\sim $0.875. However, the origin of this FM clustering configuration is still an open question. Chemical nonuniformity (Bi ion segregation) as a candidate interpretation has been explored with TEM/EDS, which can give a quantitative assessment of geometrical parameters, chemical composition and crystal structure of second phase particles. We have identified evidences for the possible Bi nonuniformity in nano-scale, which are consistent with the results from small-angle neutron scattering. This work is supported by NSF DMR-0512196.