Structural and magnetic phases of Bi1−xAxFeO3−δ (A = Sr, Pb) perovskites
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- Troyanchuk, I., Bushinsky, M., Karpinsky, D. et al. Eur. Phys. J. B (2010) 73: 375. doi:10.1140/epjb/e2010-00004-y
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The Bi1−xAxFeO3−δ (A = Sr, Pb) systems have been studied using the X-ray, neutron powder diffraction and magnetization measurements in a magnetic field up to 14 T. It was found that around x ∼ 0.06 the crystal symmetry changes from a rhombohedral (space group R3c) to pseudo-tetragonal. In the composition range 0.07 ≤ x ≤ 0.14 the phases with different symmetry of the unit cell coexist independent of synthesis conditions. The neutron powder diffraction shows that the iron ions have average oxidation state close to 3+. The magnetic structure for Bi0.5Sr0.5FeO3−δ is found to be G-type antiferromagnetic with magnetic moment of about 3.8 μB/Fe3+. The weak ferromagnetic state due to magnetoelectric interactions was revealed in the lightly doped rhombohedrally distorted compositions. No evidence for a spontaneous magnetization was observed for the pseudo-tetragonal phases. These compositions show irreversible nonlinear magnetization vs. field behavior apparently due to small local deviations from the collinearity of the magnetic moments.