7 research outputs found
Neutron Diffraction and EXAFS Studies of K<sub>2<i>x</i>/3</sub>Cu[Fe(CN)<sub>6</sub>]<sub>2/3</sub>·<i>n</i>H<sub>2</sub>O
The
crystal structure of copper hexacyanoferrate (CuHCF), K<sub>2<i>x/</i>3</sub>CuÂ[FeÂ(CN)<sub>6</sub>]<sub>2/3</sub>·<i>n</i>H<sub>2</sub>O, with nominal compositions <i>x</i> = 0.0 and <i>x</i> = 1.0 was studied by neutron
powder diffraction (NPD) and extended X-ray absorption fine structure
(EXAFS) spectroscopy. The compound crystallizes in space group <i>Fm</i>3Ì…<i>m</i>, with <i>a</i> =
10.1036(11) Ã… and <i>a</i> = 10.0588(5) Ã… for <i>x</i> = 0.0 and <i>x</i> = 1.0, respectively. Difference
Fourier maps for <i>x</i> = 0.0 show that the coordinated
water molecules are positioned at a site 192l close to vacant N positions
in the −Fe–C–N–Cu– framework, while
additional zeolitic water molecules are distributed over three sites
(8c, 32f, and 48g) in the −Fe–C–N–Cu–
framework cavities. The refined water content for <i>x</i> = 0.0 is 16.8(8) per unit cell, in agreement with the ideal 16 (<i>n</i> = 4). For <i>x</i> = 1.0, the refinement suggests
that 2.6 K atoms per unit cell (<i>x</i> = 0.98) are distributed
only over the sites 8c and 32f in the cavities, and 13.9(7) water
per unit cell are distributed over all the four positions. The EXAFS
data for Fe, Cu, and K K-edges are in agreement with the NPD data,
supporting a structure model with a linear −Fe–C–N–Cu–
framework and K<sup>+</sup> ions in the cavities
Crystal and Magnetic Structure in Co-Substituted BiFeO<sub>3</sub>
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
Crystal and Magnetic Structure in Co-Substituted BiFeO<sub>3</sub>
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
Crystal and Magnetic Structure in Co-Substituted BiFeO<sub>3</sub>
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
Crystal and Magnetic Structure in Co-Substituted BiFeO<sub>3</sub>
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
Crystal and Magnetic Structure in Co-Substituted BiFeO<sub>3</sub>
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
Crystal and Magnetic Structure in Co-Substituted BiFeO<sub>3</sub>
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