| 1. |
- Ali, S. K. Imran, et al.
(författare)
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Hydrothermal Synthesis of the Oxofluoride FeSbO2F2-An Anti-ferromagnetic Spin S=5/2 Compound
- 2017
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 56:8, s. 4662-4667
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Tidskriftsartikel (refereegranskat)abstract
- The new oxofluoride compound FeSbO2F2 was synthesized by hydro thermal techniques at 230 degrees C. Its crystal structure was determined from single-crystal Xray diffraction data. The compound crystallizes in the monoclinic space group C2/c with one crystallographic site for Fe3+ and SP3+, respectively. The crystal structure is made of [FeO2F4] octahedra and seesaw [SbO4] building blocks. These are connected to form [FeO2F2] layers and [SbO2] chains that bond together via the oxygen atoms to form the three-dimensional framework structure. Magnetic susceptibility and heat capacity measurements indicate long-range anti-ferromagnetic ordering below a Neel temperature of similar to 175 K Two-dimensional anti-ferromagnetic short-range order in the square planar net of the Fe3+ cations extends to temperatures far above the Neel temperature.
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| 2. |
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| 3. |
- Ali, Sk Imran, et al.
(författare)
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Hydrothermal Synthesis and Magnetic Characterization of the Quaternary Oxide CoMo2Sb2O10
- 2016
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 55:21, s. 11490-11496
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Tidskriftsartikel (refereegranskat)abstract
- The new quaternary layered oxide CoMo2Sb2O10 was synthesized by hydrothermal synthesis techniques, and its structure was determined from single-crystal X-ray diffraction data. CoMo2Sb2O10 crystallizes in the monoclinic space group C2/c with one Sb3+, Mo6+, and Co2+ atom site per unit cell, respectively. The crystal structure contains building units consisting of [Co2O8](n), [Mo2O8](n), and [SbO2](n) chains. These are connected through corner sharing to form charge neutral [CoMo2Sb2O10](n) layers. Thermal decomposition of CoMo2Sb2O10 starts at 550 degrees C. The magnetic susceptibility follows a Curie Weiss law above 50 K with a Curie constant of C = 3.46 emu K mol(-1) corresponding to an effective moment of mu(eff) = 5.26 mu(B) per cobalt atom and a Curie-Weiss temperature theta = -13.2 K. Short-range anti-ferromagnetic ordering dominates below 5 K. Magnetic susceptibility and heat capacity data can be successfully modeled by the predictions from an Ising linear chain with an intrachain spin exchange of ca. -7.8 K.
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| 4. |
- Ali, Sk Imran, et al.
(författare)
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Synthesis and Magnetic Properties of the Ternary Oxofluoride Fe3Sb4O6F6
- 2020
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Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-1948 .- 1099-0682. ; 2020:39, s. 3746-3752
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Tidskriftsartikel (refereegranskat)abstract
- The new compound Fe(3)Sb(4)O(6)F(6)was prepared by hydrothermal synthesis and its crystal structure was determined from single-crystal X-ray diffraction data. The synthesis was made under slightly basic conditions to prevent oxidation of Fe(2+)to Fe3+. The compound crystallizes in the cubic space groupI-43mwith separate crystallographic sites for Fe(2+)and Sb3+. Fe(3)Sb(4)O(6)F(6)is isostructural with M3Sb4O6F6(M = Co, Ni, Zn). The crystal structure is comprising distorted [FeO2F4] octahedra connected via corner sharing at F-atoms and [SbO3] trigonal pyramids that form [Sb4O6] units that connect via O-atoms to the Fe-atoms. Mossbauer spectroscopy measurements on the hydrothermal synthesis products prove the majority phase contains Fe in the oxidation state +2. Powder X-ray diffraction suggests that an additional phase of the Mossbauer sample containing Fe(3+)can be attributed to FeSbO(2)F(2)as secondary phase. Fe(3)Sb(4)O(6)F(6)exhibits antiferromagnetic order below ca. 72 K succeeded by a second magnetic phase transition at ca. 30 K. Strong antiferromagnetic spin-exchange interaction is attributed to 180 degrees Fe-F-Fe superexchange pathways identified in the crystal structure.
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| 5. |
- Hu, Shichao, et al.
(författare)
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Crystal Structure and Magnetic Properties of FeSeO3F : Alternating Antiferromagnetic S = 5/2 chains
- 2014
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 53:8, s. 4250-4256
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Tidskriftsartikel (refereegranskat)abstract
- The new oxofluoride FeSeO3F crystallizes in the space group P21/n and consists of [FeO3F]∞ zigzag chains with alternating Fe−F−Fe and Fe−O−Fe spin exchange paths. The magnetic susceptibility of FeSeO3F is largely described by an S = 5/2 Heisenberg antiferromagnetic chain with alternating antiferromagnetic spin exchanges, and FeSeO3F undergoes a long-range antiferromagnetic ordering below 45 K.
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| 6. |
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| 7. |
- Mitoudi Vagourdi, Eleni, et al.
(författare)
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Synthesis and Characterization of the Aurivillius Phase CoBi2O2F4
- 2018
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 57:15, s. 9115-9121
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Tidskriftsartikel (refereegranskat)abstract
- The new CoBi2O2F4 compound was synthesized by a hydrothermal method at 230 degrees C. Single-crystal X-ray diffraction data were used to determine the crystal structure. The compound is layered and belongs to the Aurivillius family of compounds. The present compound is the first oxo-fluoride Aurivillius phase containing Co2+. Inclusion of a d-block cation with such a low oxidation state as 2+ was achieved by partially replacing O2- with F- ions. The crystal structure is best described in the tetragonal noncentrosymmetric space group I<(4)overbar> with unit-cell parameters a = 3.843(2) angstrom and c = 16.341(8) angstrom. The crystal structure consists of two main building units: [BiO4F4] distorted cubes and [CoF6] octahedra. Interestingly, since the octahedra [CoF6] tilt between four equivalent positions, the F atoms occupy a 4-fold split position at room temperature. For the investigation of the structural disorder, Raman scattering data were collected in the range from 10 K to room temperature. As the temperature decreases, sharper phonon peaks appear and several modes clearly appear, which indicates a reduction of the disorder. Magnetic susceptibility and heat capacity measurements evidence long-range antiferromagnetic ordering below the Neel temperature of similar to 50 K. The magnetic susceptibility is in agreement with the Curie-Weiss law above 75 K with a Curie-Weiss temperature of theta(cw) = -142(2) K.
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| 8. |
- Mitoudi-Vagourdi, Eleni, et al.
(författare)
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Synthesis and Magnetic Properties of the KCu(IO3)(3) Compound with [CuO5](infinity) Chains
- 2019
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 4:12, s. 15168-15174
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Tidskriftsartikel (refereegranskat)abstract
- The new quaternary iodate KCu(IO3)(3) has been prepared by hydrothermal synthesis. KCu(IO3)(3) crystallizes in the monoclinic space group P2(1)/n with unit cell parameters a = 9.8143(4) angstrom, b = 8.2265(4) angstrom, c = 10.8584(5) angstrom,beta = 91.077(2)degrees, and z = 4. The crystals are light blue and translucent. There are three main building units making up the crystal structure: [KO10] irregular polyhedra, [CuO6] distorted octahedra, and [IO3] trigonal pyramids. The Jahn-Teller elongated [CuO6] octahedra connect to each other via corner sharing to form [CuO5](infinity) zigzag chains along [010]; the other building blocks separate these chains. The Raman modes can be divided into four groups; the lower two groups into mainly lattice modes involving K and Cu displacements and the upper two groups into mainly bending and stretching modes of [IO3E], where E represents a lone pair of electron. At low temperatures, the magnetic susceptibility is characterized by a broad maximum centered at similar to 5.4 K, characteristic for antiferromagnetic short-range ordering. Long-range magnetic ordering at T-C = 1.32 K is clearly evidenced by a sharp anomaly in the heat capacity. The magnetic susceptibility can be very well described by a spin S = 1/2 antiferromagnetic Heisenberg chain with a nearest-neighbor spin exchange of similar to 8.9 K.
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| 9. |
- Mitoudi-Vagourdi, Eleni, et al.
(författare)
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Synthesis and Physical Properties of the Oxofluoride Cu-2(SeO3)F-2
- 2018
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 57:8, s. 4640-4648
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Tidskriftsartikel (refereegranskat)abstract
- Single crystals of the new compound Cu-2(SeO3)F-2 were successfully synthesized via a hydrothermal method, and the crystal structure was determined from single-crystal X-ray diffraction data. The compound crystallizes in the orthorhombic space group Pnma with the unit cell parameters a = 7.066(4) (A) over circle, b = 9.590(4) (A) over circle, and c = 5.563(3) (A) over circle. Cu-2(SeO3)F-2 is isostructural with the previously described compounds Co2TeO3F2 and CoSeO3F2. The crystal structure comprises a framework of corner- and edge-sharing distorted [CuO3F3] octahedra, within which [SeO3] trigonal pyramids are present in voids and are connected to [CuO3F3] octahedra by corner sharing. The presence of a single local environment in both the F-19 and Se-77 solid-state MAS NMR spectra supports the hypothesis that O and F do not mix at the same crystallographic positions. Also the specific phonon modes observed with Raman scattering support the coordination around the cations. At high temperatures the magnetic susceptibility follows the Curie-Weiss law with Curie temperature of Theta = -173(2) K and an effective magnetic moment of mu(eff) similar to 2.2 mu(B). Antiferromagnetic ordering below similar to 44 K is indicated by a peak in the magnetic susceptibility. A second though smaller peak at similar to 16 K is tentatively ascribed to a magnetic reorientation transition. Both transitions are also confirmed by heat capacity measurements. Raman scattering experiments propose a structural phase instability in the temperature range 6-50 K based on phonon anomalies. Further changes in the Raman shift of modes at similar to 46 K and similar to 16 K arise from transitions of the magnetic lattice in accordance with the susceptibility and heat capacity measurements.
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| 10. |
- Stingaciu, Marian, et al.
(författare)
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Magnetoresistivity in CoFe(2)O(4)-BaTiO(3) composites produced by spark plasma sintering
- 2011
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 110:4, s. 044903-
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Tidskriftsartikel (refereegranskat)abstract
- Ceramic composites of (CoFe(2)O(4))(x)-(BaTiO(3))((1-x)) with x = 0.20, 0.25, and 0.30 have been synthesized by spark plasma sintering at 1000 degrees C under a uniaxial pressure of 75 MPa using commercially available nanopowders as starting materials. The composites reveal a negative magnetoresistivity effect of about -1% at room temperature. An enhancement was observed at lower temperatures, and an effect of -4.1% was found in the composite with x 0.30 at 150 K by applying an external magnetic field of 25 kOe. The temperature dependence of the resistivity indicates variable range hopping involved in charge transport.
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