| 1. |
- Ivanov, Sergey A., et al.
(författare)
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Structural and magnetic properties of nickel antimony ferrospinels
- 2015
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Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584 .- 1879-3312. ; 158, s. 127-137
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Tidskriftsartikel (refereegranskat)abstract
- Spinel-type compounds of Fe-Ni-Sb-O system were synthesized as polycrystalline powders. The crystal and magnetic properties were investigated using X-ray and neutron powder diffraction, Mossbauer and X-ray absorption spectroscopy and magnetization measurements. The samples crystallize in the cubic system, space group Fd - 3 m. The distribution of cations between octahedral and tetrahedral sites was refined from the diffraction data sets using constraints imposed by the magnetic, Mossbauer and EDS results and the ionic radii. The cation distribution and the temperature dependence of the lattice parameter (a) and the oxygen positional parameter (u) were obtained. A chemical formula close to Fe0.8Ni1.8Sb0.4O4 was determined, with Sb5+ cations occupying octahedral sites, and Fe3+ and Ni2+ occupying both tetrahedral and octahedral sites. Fe3+ mainly (85/15 ratio) occupy tetrahedral sites, and conversely Ni2+ mainly reside on octahedral ones. The magnetic unit cell is the same as the crystallographic one, having identical symmetry relations. The results indicate that the compounds have a collinear ferrimagnetic structure with antiferromagnetic coupling between the tetrahedral (A) and octahedral (B) sites. Uniquely, the temperature dependence of the net magnetization of this rare earth free ferrimagnet exhibits a compensation point.
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| 2. |
- Kaleva, G M, et al.
(författare)
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Phase Transitions of (Cu,Ni)(3)TeO(6) Solid Solutions
- 2011
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Ingår i: Inorganic Materials (Neorganicheskie materialy). - 0020-1685 .- 1608-3172. ; 47:10, s. 1132-1140
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Tidskriftsartikel (refereegranskat)abstract
- (Cu,Ni)(3)TeO(6) solid solutions with the bixbyite (pseudocorundum) and ilmenite structures have been prepared by solid-state reactions and characterized by a variety of techniques. We have studied the effect of nickel substitution for copper on the phase composition of the materials, examined the microstructure of ceramic samples, and measured their magnetic susceptibility, heat capacity, permittivity, and loss tangent as functions of temperature. This allowed us to reveal dielectric anomalies related to structural phase transitions and to determine the antiferromagnetic ordering temperatures of the (Cu,Ni)(3)TeO(6) ceramics.
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| 3. |
- Kumar, Anil P., et al.
(författare)
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Composition driven structural transition in La2-xSrxCuRuO6 (0 <= x <= 1) double perovskites
- 2017
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 693, s. 1096-1101
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Tidskriftsartikel (refereegranskat)abstract
- We report results of detailed structural investigations on the system La2-xSrxCuRuO6 (0 <= x <= 1) as a function of composition using neutron powder diffraction. Our results reveal that this series of compounds exhibit an interesting structural transition manifested through Sr doping; with Ru in single valency, in end members, and mixed valency otherwise. The end members La2CuRuO6 and LaSrCuRuO6 crystallize in monoclinic structures with space group P2(1)/n. However, the compositions with intermediate Sr doping (x = 0.2 and 0.8) crystallize in triclinic structure with space group P-1, albeit with minute distortions. The detailed structural studies by neutron powder diffraction at room temperature and at 10 K, for compositions, x = 0.2, 0.8 and 1 are presented. While magnetic measurements are indicative of ferro and antiferromagnetic like transitions for x = 0 and x > 0 respectively, neutron diffraction patterns collected at 10 K and 30 K across the characteristic transition temperature suggested by the magnetic data, do not show any extra peaks or extra intensity at lower temperature as compared to the high temperature, thus, establishing the absence of any long-range magnetic ordering in these samples.
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