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Magnetic Susceptibility Data (magnetic + susceptibility_data)
Selected AbstractsTetranuclear Nickel Complexes Composed of Pairs of Dinuclear LNi2 Fragments Linked by 4,4,-Bipyrazolyl, 1,4-Bis(4,-pyrazolyl)benzene, and 4,4,-Bipyridazine: Synthesis, Structures, and Magnetic PropertiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2007Vasile Lozan Abstract The ability of the ligands 4,4,-bipyrazolyl (H2bpz), 1,4-bis(4,-pyrazolyl)benzene (H2bpzb), and 4,4,-bipyridazine (bpdz) to link two dioctahedral LNi2 units has been examined. Thefollowing complexes were prepared: [L1NiII2(Hbpz)][BPh4] (6[BPh4]), [L1NiII2(bpdz)][ClO4]2 (7[ClO4]2), [(L1NiII2)2(bpzb)][BPh4]2 (8[BPh4]2), and [(L2NiII2)2(bpz)][BPh4]2 (9[BPh4]2), where (L1)2, and (L2)2, represent macrocyclic hexaaza-dithiophenolate ligands. All complexes have been characterised by UV/Vis spectroscopy, IR spectroscopy, and X-ray crystallography. Whereas (Hbpz), and bpdz in 6[BPh4]2 and 7[ClO4]2 act as bidentate ligands coordinating to only one [LNi2]2+ unit, in 8[BPh4]2 and 9[BPh4]2 the (bpzb)2, and(bpz)2, units are tetradentate linkers. This is qualitatively explained in terms of the absence or presence of steric repulsions between the tBu groups of the supporting ligands and the length of the coligands. The structures of the tetranuclear complexes differ mainly in the distance between the center of the Ni···Ni axes of the isostructural [LNi2] units {14.040(1) Å in 8[BPh4]2, 9.184(1) Å in 9[BPh4]2}. The two Ni2pyrazolato planes in 9[BPh4]2 are coplanar. An analysis of the temperature-dependent magnetic susceptibility data for 9[BPh4]2 reveals the presence of weak ferromagnetic exchange interactions between the NiII ions in the binuclear [L2Ni2] subunits with values for the magnetic exchange constant J1 of 23.97 cm,1 (H = ,2JS1S2). The exchange coupling across the dipyrazolato bridge is less than 0.1 cm,1, suggesting that no significant interdimer exchange coupling occurs in 9[BPh4]2. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Coordination Chemistry of N,N,N,,N, -Tetraethylpyridine-2,6-dithiocarboxamide (S -dept) , X-ray Crystal Structures and Magnetic Properties of [Co(S -dept)X2] (X = Br, I, and NCS)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2005Ramesh Kapoor Abstract Mononuclear cobalt(II) complexes [Co(S -dept)X2] [X = Br (1), I (2) and NCS (3)] were synthesized using N,N,N,,N, -tetraethylpyridine-2,6-dithiocarboxamide (S -dept), and characterised by conductivity, spectral and single-crystal X-ray diffraction studies. These studies reveal that the compounds consist of discrete monomeric molecules in which the cobalt atoms are five-coordinate in an environment that is best described as being distorted square-pyramidal. In dimethylformamide the iodo complex shows significant ionic dissociation (1:1 electrolyte) and its crystal field absorption spectrum is interpretable in terms of an octahedral structure [Co(S -dept)(DMF)2I]+. The temperature dependence of the magnetic susceptibility data is indicative of a high-spin compound with an important zero-field splitting. The best fitwas obtained with |D| = 20.5 cm,1 and g = 2.53 for 1, |D| = 14.2 cm,1 and g = 2.38 for 2 and |D| = 17.7 cm,1 and g = 2.35 for 3. The X-band EPR spectra at low temperature is also characteristic of an S = 3/2 state with important zero-field splitting. The most important band appears at low fields (ca. 1200 G). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] In situ identification, pairing, and classification of meteorites from Antarctica through magnetic susceptibility measurementsMETEORITICS & PLANETARY SCIENCE, Issue 3 2006Luigi Folco Magnetic susceptibility measurements carried out with a pocket meter (SM30) during the 2003/04 PNRA meteorite collection expedition to northern Victoria Land (Antarctica) proved to be a rapid, sensitive, non-destructive means for the in situ identification, pairing, and classification of meteorites. In blue ice fields characterized by the presence of moraines and glacial drifts (e.g., Miller Butte, Roberts Butte, and Frontier Mountain), magnetic susceptibility measurements allowed discrimination of meteorites from abundant terrestrial stones that look like meteorites thanks to the relatively high magnetic susceptibility of the former with respect to terrestrial rocks. Comparative measurements helped identify 16 paired fragments found at Johannessen Nunataks, thereby reducing unnecessary duplication of laboratory analyses and statistical bias. Following classifications schemes developed by us in this and previous works, magnetic susceptibility measurements also helped classify stony meteorites directly in the field, thereby providing a means for selecting samples with higher research priority. A magnetic gradiometer capable of detecting perturbations in the Earth's magnetic field induced by the presence of meteorites was an efficient tool for locating meteorites buried in snow along the downwind margin of the Frontier Mountain blue ice field. Based on these results, we believe that magnetic sensors should constitute an additional payload for robotic search for meteorites on the Antarctic ice sheet and, by extension, on the surface of Mars where meteorite accumulations are predicted by theoretical works. Lastly, magnetic susceptibility data was successfully used to crosscheck the later petrographic classification of the 123 recovered meteorites, allowing the detection of misclassified or peculiar specimens. [source] PRESELI DOLERITE BLUESTONES: AXE-HEADS, STONEHENGE MONOLITHS, AND OUTCROP SOURCESOXFORD JOURNAL OF ARCHAEOLOGY, Issue 1 2006OLWEN WILLIAMS-THORPE Summary. Chemical compositions and magnetic susceptibility data were compared for 12 dolerite bluestone implements including axes, axe-hammers and battle-axes, 11 Stonehenge monoliths (chemical data only), and potential source outcrops in Preseli, South Wales. Most of the studied artefacts are of spotted dolerite, a small number being unspotted dolerite. Bivariate graphs, discriminant analysis and t-tests were used singly and in combination to show, respectively, that the implements found at sites in England are mainly similar to Stonehenge monoliths, while the implements found in Wales have a variety of compositions and are much less similar to Stonehenge monoliths. The dichotomy between English and Welsh dolerite bluestone implements could be explained by exploitation of different Preseli outcrops or erratic assemblages derived from them. A small number of spotted dolerite implements have previously been shown to have chemical compositions atypical of and marginal to Preseli, suggesting the possibility of a source of spotted dolerite outside Preseli. Previously published analytical data in combination with the new implement/outcrop comparisons presented in this paper support derivation of the majority of analysed Stonehenge monoliths at one particular outcrop within the group of four identified by Thorpe et al. 15 years ago. Analysis of all the extant bluestone monoliths at Stonehenge (now possible using non-destructive methods) would allow progress in identifying monolith outcrop sources, and in understanding the links with the bluestone axe trade. [source] Isosymmetrical phase transition in ,-YbV4O8ACTA CRYSTALLOGRAPHICA SECTION B, Issue 6 2008Karen Friese The structure of YbV4O8 is related to the CaFe2O4 structure type. VO6 octahedra form a three-dimensional framework with tunnels in which the Yb3+ ions are incorporated. Two different polymorphs , and , are known and differ mainly in the arrangement of the Yb ions within the framework. We studied the structure and magnetic properties of ,-YbV4O8 as a function of temperature. At approximately 70,K ,-YbV4O8 undergoes a first-order isosymmetrical phase transition (P21/n,P21/n). While in the high-temperature , phase the three V3+ and one V4+ are disordered over the four symmetrically independent octahedral sites, in the low-temperature ,, phase complete charge ordering is observed. The transition is accompanied by a paramagnetic,paramagnetic anomaly in the magnetic susceptibility data which can be interpreted on the basis of spin-gap formation. The transition mechanism in the , polymorph is very similar to that observed earlier in the , polymorph at 185,K. [source] Exploring the location and function of a Late Neolithic house at Crossiecrown, Orkney by geophysical, geochemical and soil micromorphological methodsARCHAEOLOGICAL PROSPECTION, Issue 1 2010Richard Jones Abstract Magnetic prospection was instrumental in the discovery of a multiphase Neolithic settlement at Crossiecrown on Mainland Orkney. Subsequent excavation revealed a number of structures, including a large circular walled house of Late Neolithic date with a range of well-defined architectural features in its interior. This paper presents the discovery, excavation and in particular the functional analysis of this house. Soil micromorphology established the sequence from the house's initial floor construction to its abandonment. On the basis of multi-element and magnetic susceptibility data obtained from analysis of samples taken from the floor of the house, several element distributions were found to be distinctive in the way they correlated with some of the house's ,fixed furniture' and moreover with the distributions of certain artefacts, notably the stone tools. The archaeological implications of these findings are discussed. Copyright © 2010 John Wiley & Sons, Ltd. [source] | ||||||||||