Convergent-beam electron diffraction study of the low-temperature ferromagnetic insulator phase of La1-xSrxMnO3 (x=0.11, 0.12)

The low-temperature ferromagnetic insulator (FMI) phase of La1-xSrxMnO3 (x = 0.11,0.12) was investigated by convergent-beam electron diffraction (CBED ) together with selected-area electron diffraction (SAED). We have revealed that the FMI phase belongs to the triclinic space group P (1) over bar, an d has a unit cell of similar to 2a(c) X 4b(c) x 4c(c), where a(c), b(c), c( c) are lattice parameters in the pseudocubic perovskite notation. These fin dings indicate that tile FMI phase is neither the re-entrant phase of the h igh temperature phase (similar to root 2a(c) x 2 rootb(c) x 2c(c)) as repor ted by Kawano et al. nor the polaron-ordering phase with a unit cell of (si milar to 2a(c) x 2b(c) x 4c(c)) as proposed by Yamada et al.