Crystal
and Magnetic Structure in Co-Substituted BiFeO<sub>3</sub>
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Abstract
Ultra-high-resolution neutron diffraction
studies of BiFe<sub>0.8</sub>Co<sub>0.2</sub>O<sub>3</sub> show a
transition from a cycloidal
space modulated spin structure at <i>T </i>= 10 K to a collinear
G-type antiferromagnetic structure at <i>T </i>= 120 K.
The model of antiparallel directions of Fe<sup>3+</sup> and Co<sup>3+</sup> magnetic moments at the shared Wyckoff position describes
well the observed neutron diffraction intensities. On heating above
RT, the crystal structure of BiFe<sub>0.8</sub>Co<sub>0.2</sub>O<sub>3</sub> changes from a rhombohedral <i>R</i>3<i>c</i> to a monoclinic <i>Cm</i>. At 573 K only the <i>Cm</i> phase is present. The collinear C-type antiferromagnetic structure
is present in the <i>Cm</i> phase of BiFe<sub>0.8</sub>Co<sub>0.2</sub>O<sub>3</sub> at RT after annealing