  Samarium doped BiFeO3 compounds having nano-size crystallites were prepared
by the ethylene glycol assisted sol-gel synthesis method. X-ray diffraction and
SEM measurements as well as Raman spectroscopy and FTIR experiments were used
to clarify the evolution of the crystal structure on microscopic and local
scale levels in the compounds having formula Bi1-xSmxFeO3, where x equals from
0 to 1. Magnetization measurements along with the structural data were used to
determine a correlation between magnetic properties and crystal structure of
the compounds. The compounds with from x 0.1-0.2 are characterized by the
sequence of the structural transitions driven by the dopant increase, from the
polar rhombohedral phase to the non-polar orthorhombic phase via two-phase
regions characterized by the presence of the anti-polar orthorhombic phase. The
concentration regions ascribed to a coexistence of the rhombohedral and the
anti-polar orthorhombic phases as well as theanti-polar orthorhombic and the
non-polar orthorhombic phases are observed in the ranges from 0.12 to 0.15 and
from 0.15 to 0.18 respectively. The compounds having single-phase rhombohedral
structure are characterized by a release of remnant magnetization as compared
to ceramics with similar chemical compositions but synthesized by the
solid-state reaction method and having microscopic size crystallites. A
correlation between the type of structural distortion, morphology of
crystallites and an onset of remnant magnetization is discussed highlighting a
difference in the evolution of crystal structure and magnetization observed for
the Sm-doped ceramics prepared by modified sol-gel method and conventional
solid-state reaction technique.
