Structural, Magnetic and Electrical Properties of A-Site-Ordered Perovskites

The crystal structure, magnetic and electrical properties of A-site-ordered perovskite manganites Ln1/2Ba1/2MnO3 (Ln=rare earth) were investigated. In the ordered Ln1/2Ba1/2MnO3 (Ln = Sm-Y), a new charge/orbital ordering pattern was found. Electron diffraction studies revealed a series of superlattice reflections with modulation vectors at q2 = (1/2, 1/2, 1/2) as well as at q1= (1/4, 1/4, 0) in the tetragonal setting (ap × ap × 2ap, ap being the cubic perovskite lattice parameter) . Together with the results of the resonant X-ray scattering, a model for the three-dimensional charge/orbital ordering is proposed.