Neutron Diffraction and EXAFS Studies of K_2<i>x</i>/3Cu[Fe(CN)₆]_2/3·<i>n</i>H₂O

The crystal structure of copper hexacyanoferrate (CuHCF), K_2<i>x/</i>3Cu­[Fe­(CN)₆]_2/3·<i>n</i>H₂O, 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>3̅<i>m</i>, with <i>a</i> = 10.1036(11) Å and <i>a</i> = 10.0588(5) Å 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⁺ ions in the cavities

Crystal and Magnetic Structure in Co-Substituted BiFeO₃

Ultra-high-resolution neutron diffraction studies of BiFe_0.8Co_0.2O₃ 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 Fe³⁺ and Co³⁺ magnetic moments at the shared Wyckoff position describes well the observed neutron diffraction intensities. On heating above RT, the crystal structure of BiFe_0.8Co_0.2O₃ 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_0.8Co_0.2O₃ at RT after annealing

Crystal and Magnetic Structure in Co-Substituted BiFeO₃

Ultra-high-resolution neutron diffraction studies of BiFe_0.8Co_0.2O₃ 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 Fe³⁺ and Co³⁺ magnetic moments at the shared Wyckoff position describes well the observed neutron diffraction intensities. On heating above RT, the crystal structure of BiFe_0.8Co_0.2O₃ 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_0.8Co_0.2O₃ at RT after annealing

Crystal and Magnetic Structure in Co-Substituted BiFeO₃

Ultra-high-resolution neutron diffraction studies of BiFe_0.8Co_0.2O₃ 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 Fe³⁺ and Co³⁺ magnetic moments at the shared Wyckoff position describes well the observed neutron diffraction intensities. On heating above RT, the crystal structure of BiFe_0.8Co_0.2O₃ 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_0.8Co_0.2O₃ at RT after annealing

Crystal and Magnetic Structure in Co-Substituted BiFeO₃

Ultra-high-resolution neutron diffraction studies of BiFe_0.8Co_0.2O₃ 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 Fe³⁺ and Co³⁺ magnetic moments at the shared Wyckoff position describes well the observed neutron diffraction intensities. On heating above RT, the crystal structure of BiFe_0.8Co_0.2O₃ 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_0.8Co_0.2O₃ at RT after annealing

Crystal and Magnetic Structure in Co-Substituted BiFeO₃

Ultra-high-resolution neutron diffraction studies of BiFe_0.8Co_0.2O₃ 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 Fe³⁺ and Co³⁺ magnetic moments at the shared Wyckoff position describes well the observed neutron diffraction intensities. On heating above RT, the crystal structure of BiFe_0.8Co_0.2O₃ 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_0.8Co_0.2O₃ at RT after annealing

Crystal and Magnetic Structure in Co-Substituted BiFeO₃

Ultra-high-resolution neutron diffraction studies of BiFe_0.8Co_0.2O₃ 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 Fe³⁺ and Co³⁺ magnetic moments at the shared Wyckoff position describes well the observed neutron diffraction intensities. On heating above RT, the crystal structure of BiFe_0.8Co_0.2O₃ 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_0.8Co_0.2O₃ at RT after annealing