Crystal structure and magnetic properties of two new cobalt selenite halides: Co5(SeO3)4X2 (X=Cl, Br) |
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Authors: | Richard Becker Mladen Prester Ping Hui Lin Mats Johnsson Ivica Zivkovic |
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Institution: | a Department of Inorganic Chemistry, Stockholm University, S-106 91 Stockholm, Sweden b Institute of Physics, P.O. Box 304, HR-10000 Zagreb, Croatia c Institut de Physique de la Matiere Complexe, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland d Institute of Physics, Academia Sinica Nankang, Taipei 11529, Taiwan, ROC |
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Abstract: | Two new isostructural cobalt selenite halides Co5(SeO3)4Cl2 and Co5(SeO3)4Br2 have been synthesized. They crystallize in the triclinic system space group P−1 with the following lattice parameters for Co5(SeO3)4Cl2: a=6.4935(8) Å, b=7.7288(8) Å, c=7.7443(10) Å, α=66.051(11)°, β=73.610(11)°, γ=81.268(9)°, and Z=1. The crystal structures were solved from single-crystal X-ray data, R1=3.73 and 4.03 for Co5(SeO3)4Cl2 and Co5(SeO3)4Br2, respectively. The new compounds are isostructural to Ni5(SeO3)4Br2.Magnetic susceptibility measurements on oriented single-crystalline samples show anisotropic response in a broad temperature range. The anisotropic susceptibility is quantitatively interpreted within the zero-field splitting schemes for Co2+ and Ni2+ ions. Sharp low-temperature susceptibility features, at TN=18 and 20 K for Co5(SeO3)4Cl2 and Co5(SeO3)4Br2, respectively, are ascribed to antiferromagnetic ordering in a minority magnetic subsystem. In isostructural Ni5(SeO3)4Br2 magnetically ordered subsystem represents a majority fraction (TN=46 K). Nevertheless, anisotropic susceptibility of Ni5(SeO3)4Br2 is dominated at low temperatures by a minority fraction, subject to single-ion anisotropy effects and increasing population of Sz=0 (singlet) ground state of octahedrally coordinated Ni2+. |
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Keywords: | Oxo-halide Lone-pair elements Crystal structure determination Magnetic susceptibility Zero-field splitting Single-ion anisotropy |
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