1998/12/22 by P. G. Radaelli, D. E. Cox, L. Capogna +3
Chemistry · Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Antiferromagnetism #Charge (physics) #Charge ordering #Chemistry #Condensed matter physics #Crystal structure #Crystallography #Lattice (music) #Magnetic and transport properties of perovskites and related materials #Materials science #Neutron diffraction #Octahedron #Orthorhombic crystal system #Physics #Quantum mechanics #Rare-earth and actinide compounds #Rietveld refinement #Superlattice #Superstructure #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.59.14440
22 pages, 9 figures, submitted to Physical Review B
arxiv created 1998/12/22 · openalex publication_date 1999/06/01 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The crystallographic (charge-ordered) and magnetic superstructures of La0.333Ca0.667MnO3 were studied by high-resolution synchrotron x-ray and neutron powder diffraction. In the antiferromagnetic structure, which was refined using a noncollinear model, the a lattice parameter is tripled and the c lattice parameter is doubled with respect to the average crystallographic unit cell (Pnma setting). The crystallographic structure below the charge-ordering temperature (TCO\ensuremath∼260K) is characterized by ordering of the d_z2 orbitals of the Jahn-Teller-distorted Mn3+O6 octahedra in the orthorhombic ac plane, and the appearance of superlattice peaks in the x-ray patterns corresponding to a tripling of the a axis lattice parameter. The intensities of the superlattice peaks can be accounted for satisfactorily in terms of ordering of the Mn3+ cations in sites as far apart as possible in the ac plane (``Wigner-crystal'' model) and transverse displacements of the Mn4+O6 octahedra in the c direction. These results are not consistent with a recently proposed model based on transmission electron microscopy (TEM) data in which the Mn3+O6 octahedra are arranged in a bi-stripe pattern (``bi-stripe'' model). In particular, the large longitudinal stripe modulation revealed by TEM is not observed, suggesting that the TEM data may not be representative of the bulk sample. Within the framework of the Wigner-crystal model, the magnetic structure at 1.5 K and the charge-ordered superstructures at 160 and 1.5 K were refined from the neutron data.