A-site ordered manganites LnBaMn1.96Fe0.04O5 and LnBaMn1.96Fe0.04O6 are investigated by x-ray full-profile diffraction and Moessbauer spectroscopy. Powder samples were oriented with preferred orientation of platy crystallites in the plane of sample s
urface. March-Dollase function of preferred orientation was employed in analysing both the Rietveld patterns and the Mossbauer spectra. Combined effects of preffered orientation and vibrational anisotropy on the line area asymmetry of Mossbauer doublet are analysed. Constructive and destructive interference between the effects of texture and vibrational anisotropy is observed in LnBaMn1.96Fe0.04O6 and LnBaMn1.96Fe0.04O5, respectively. Both series of the manganites show the main axis of electric field gradient perpendicular to layers (Vzz along c) with Vzz>0 in oxygen-poor series and Vzz<0 in oxygen-rich series. Charge-orbital order (COO) melting around Fe dopants explains the single-site spectra observed for several Ln in both O5 and O6 series, except LaBaMn1.96Fe0.04O5. However, the short-range COO persists to be observed in magnetization and in Rietveld patterns.
While synthesizing the single crystals of novel materials is not always feasible, orienting the layered polycrystals becomes an attractive method in the studies of angular dependencies of inelastic scattering of x-rays or neutrons. Putting in use the
Rietveld analysis of layered structures in novel manganites and cuprates we develop the studies of their anisotropic properties with oriented powders instead of single crystals. Densities of phonon states (DOS) and atomic thermal displacememts (ATD) are anisotropic in the A-site ordered manganites LnBaMn2Oy of both y=5 and y=6 series (Ln=Y, La, Sm, Gd). We establish the angular dependence of DOS on textures of arbitrary strengths, link the textures observed by x-ray and gamma-ray techniques, and solve the problem of disentanglement of Goldanskii-Karyagin effect (GKE) and texture in Moessbauer spectra.
