Modeling the crystallographic structure of Ho(Ni,Co,Mn)O_3±δ perovskite-type manganite

Crystallographic and microstructural properties of Ho(Ni,Co,Mn)O_3±δ perovskite-type multiferroic material are reported. Samples were synthesized with a modified polymeric precursor method. The synchrotron X-ray powder diffraction (SXRPD) technique associated to Rietveld refinement method was used to perform structural characterization. The crystallographic structures, as well as microstructural properties, were studied to determine unit cell parameters and volume, angles and atomic positions, crystallite size and strain. X-ray energies below the absorption edges of the transition metals helped to determine the mean preferred atomic occupancy for the substituent atoms. Furthermore, analyzing the degree of distortion of the polyhedra centered at the transitions metal atoms led to understanding the structural model of the synthesized phase. X-ray photoelectron spectroscopy (XPS) was performed to evaluate the valence states of the elements, and the tolerance factor and oxygen content. The obtained results indicated a small decrease distortion in structure, close to the HoMnO₃ basis compound. In addition, the substituent atoms showed the same distribution and, on average, preferentially occupied the center of the unit cell.