Search results for "Magnetism"
showing 10 items of 1934 documents
Focal Length Measuring Technique Using The Talbot Effect
1987
The Talbot effect - or self-imaging phenomenon - is applied to the measurement of focal lengths. The technique only requires axial distances to be measured and is suitable for both converging and diverging thick lenses.
Hybrid Molecular Magnets Obtained by Insertion of Decamethylmetallocenium Cations into Layered, Bimetallic Oxalate Complexes: [ZIIICp*2][MIIMIII(ox)3…
2000
A new series of hybrid organometallic - inorganic layered magnets with the formula [Z(III)Cp*2][M(II)M(III)(ox)3] (Z(III) = Co, Fe; M(III) = Cr, Fe; M(II) = Mn, Fe, Co, Cu, Zn; ox = oxalate; Cp* = pentamethylcyclopentadienyl) has been prepared. All of these compounds are isostructural and crystallize in the monoclinic space group C2/m, as found by X-ray structure analysis. Their structure consists of an eclipsed stacking of the bimetallic oxalate-based extended layers separated by layers of organometallic cations. These salts show spontaneous magnetization below To, which corresponds to the presence of ferro-, ferri-, or canted antiferromagnetism. Compounds in which the paramagnetic deca-me…
Solid- and solution-state studies of the novel mu-dicyanamide-bridged dinuclear spin-crossover system {[(Fe(bztpen)]2[mu-N(CN)2]}(PF6)3 x n H2O.
2005
The mononuclear diamagnetic compound {Fe(bztpen)[N(CN)2]} (PF6)CH3OH (1) (bztpen = N-benzyl-N,N′,N′- tris(2-pyridylmethyl)ethylenediamine) has been synthesized and its crystal structure studied. Complex 1 can be considered to be the formal pre-cursor of two new dinuclear, dicyanamide-bridged iron(II) complexes with the generic formula {[(Fe(bztpen)]2[μN(CN)2]}(PF6) 3·nH2O (n = 1 (2) or 0 (3)), which have been characterized in the solid state and in solution. In all three complexes, the iron atoms have a distorted [FeN6] octahedral coordination defined by a bztpen ligand and a terminal (1) or a bridging dicyanamide ligand (2 and 3). In the solid state, 2 and 3 can be considered to be molecu …
Breathing effect in a cobalt phosphonate upon dehydration/rehydration: a single-crystal-to-single-crystal study.
2013
Two cobalt phosphonates, [Co2(2,2′-bpy)2(H2O)(pbtcH)] (1) and [Co2(H2O)(pbtcH)(phen)2] (2; pbtcH5=5-phosphonatophenyl-1,2,4-tricarboxylic acid, 2,2′-bpy=2,2′-bipyridine, phen=1,10-phenanthroline), with layer structures are reported. Compound 1 contains O-C-O and O-P-O bridged tetramers of Co4, which are further connected by pbtcH(4-) units to form a layer. In compound 2, the cobalt tetramers made up of water-bridged Co2 dimers and O-P-O linkages are connected into a layer by pbtcH(4-) units. Upon dehydration, compounds 1 and 2 experience single-crystal-to-single-crystal (SC-SC) structural transformations to form [Co2(2,2′-bpy)2(pbtcH)] (1 a) and [Co2(pbtcH)(phen)2] (2 a), respectively. The …
Spontaneous magnetostriction and thermal expansibility of TmFeO3 and LuFeO3 rare earth orthoferrites
2001
Abstract At low temperatures the TmFeO3 orthoferrite shows a strong spontaneous magnetostriction generated by rare earth Tm atoms. This effect essentially depends on the temperature and orientation of the weak ferromagnetism vector of the Fe sublattice and reaches largest values for the directions [1 0 0] and [0 0 1]. The spin reorientation process in TmFeO3 marks itself mainly in the change of the signs of the linear thermal expansion coefficients in the directions mentioned above. Some additional singularities of thermal dependencies of expansion coefficients are observed below 20 K, which may be due to a magnetic compensation effect in the investigated orthoferrite.
Spin structure and spin Hall magnetoresistance of epitaxial thin films of the insulating non-collinear antiferromagnet SmFeO 3
2019
We report a combined study of imaging the antiferromagnetic (AFM) spin structure and measuring the spin Hall magnetoresistance (SMR) in epitaxial thin films of the insulating non-collinear antiferromagnet SmFeO3. X-ray magnetic linear dichroism photoemission electron microscopy measurements reveal that the AFM spins of the SmFeO3(1 1 0) align in the plane of the film. Angularly dependent magnetoresistance measurements show that SmFeO3/Ta bilayers exhibit a positive SMR, in contrast to the negative SMR expected in previously studied collinear AFMs. The SMR amplitude increases linearly with increasing external magnetic field at higher magnetic fields, suggesting that field-induced canting of …
Molecular and electronic structure of square-planar nickel(ii), nickel(iii) and nickel(iii)π-cation radical complexes with a tetradentate o-phenylene…
2005
The molecular and electronic structures of the electron transfer series of four-coordinate square-planar nickel complexes with the ligand o-phenylenebis(N'-methyloxamidate), [NiL]z (z = 2-, 1-, 0), have been evaluated by DFT and TDDFT calculations, and most of their experimentally available structural and spectroscopic properties (X. Ottenwaelder et al., Dalton Trans., 2005, DOI: 10.1039/b502478a) have been reasonably reproduced at the B3LYP level of theory. The anionic species [NiL]2- and [NiL]- are genuine low-spin nickel II and nickel III complexes with diamagnetic singlet (S = 0) and paramagnetic doublet (S = 1/2) states, respectively. The nickel III complex presents shorter Ni-N(amidat…
The solubility of Co in TiO2 anatase and rutile and its effect on the magnetic properties
2009
Co-doped anatase and rutile bulk-samples prepared by the sol-gel technique are found to be paramagnetic at room-temperature. Only further annealing in Ar/H{sub 2} gas results in a ferromagnetic behavior. X-ray diffraction and electron-microscope studies reveal for low doping levels =4%. The observed Co oxides are reduced by Ar/H{sub 2} to Co metal. The room-temperature ferromagnetism can therefore be traced back to a segregation of metallic Co. - Graphical abstract: Co-doped anatase and rutile bulk-samples prepared by the sol-gel technique are paramagnetic at room-temperature. Further annealing in Ar/H{sub 2} gas results in a ferromagnetic behavior. X-ray diffraction and electron-microscope…
Hybrid magnetic materials based on layered double hydroxides: from the chemistry towards the applications
2014
Layered double hydroxides (LDHs) are the leitmotiv of this dissertation. Contradicting the assertion that “any past was better”, LDHs have been continuously revisited from the middle of the twentieth century, and represent an excellent example of the never-ending beauty of Chemistry. New synthetic perspectives are giving a new impetus to LDH chemistry, which among hybrid materials, are finding their heyday. This is resulting in novel materials and also paving the way for new fundamental and practical insights. This dissertation is focused on magnetic LDHs, and for the sake of clarity it is organized in three main parts: we will move from basic synthetic and physical aspects of LDHs, through…
Understanding Paleomagnetic Rotations in Sicily: Thrust Versus Strike-Slip Tectonics
2018
The paleomagnetic investigation of the western Sicily Maghrebian belt has revealed since the 1970s that large clockwise rotations up to 140° with respect to the Hyblean-African foreland occurred synchronous with Tertiary shortening of the chain. The observation that rotations decrease stepwise from internal to external tectono-stratigraphic units led in the 1990s to a widely accepted model postulating that rotational thrust-sheet emplaced during forward orogenic propagation. More recently, other authors suggested that clockwise rotations from Sicily are conversely the result of late orogenic dextral strike-slip tectonics. Here we report on a paleomagnetic investigation of 30 Jurassic-Eocene…