Search results for "Paramagnetism"
showing 10 items of 354 documents
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 …
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…
Polarized neutron diffraction and Mössbauer spectral study of short-range magnetic correlations in the ferrimagnetic layered compounds(PPh4)[FeIIFeII…
2002
Short-range antiferromagnetic correlations have been studied in the layered compounds (PPh 4 ) [Fe I I Fe I I I (ox) 3 ] and (NBu 4 ) [Fe I I Fe I I I (ox) 3 ] by neutron polarization analysis and Mossbauer spectroscopy. Polarized neutron diffraction profiles obtained between 2 and 50 K on (d 2 0 -PPh 4 ) [Fe I I Fe I I I (ox) 3 ] show no magnetic Bragg scattering; the lack of such scattering indicates the absence of long-range magnetic order. However, a broad asymmetric feature observed at a Q of ca. 0.8 A - 1 is attributed to two-dimensional short-range magnetic correlations, which are described by a Warren function. The correlation length is ca. 50 A between 2 and 30 K and then decreases…
Effect of cation disorder on the magnetic properties ofSr2Fe1−xGaxReO6(0<x<0.7)double perovskites
2007
The effect of diamagnetic dilution of the Fe sublattice on the structural and magnetic properties of the double perovskite Sr{sub 2}Fe{sub 1-x}Ga{sub x}ReO{sub 6} (0 =}0.4 is detected by x-ray structural analysis accompanied by the observation of a magnetically ordered and a paramagnetic phase in the corresponding Moessbauer spectra. Below 20% Ga content, Ga statistically dilutes the -Fe-O-Re-O-Fe- double-exchange pathways. Phase separation begins at 20% Ga substitution; between 20% and 40% ofmore » Ga content, the paramagnetic Ga-based phase does not contain any Fe. The Fe-containing, paramagnetic cubic phases which can be detected by Moessbauer spectroscopy first appear for x=0.4.« less
Monitoring the Early Steps of Unfolding of Dicalcium and Mono-Ce3+-Substituted Forms of P43M Calbindin D9k
2003
Early steps of unfolding of P43M Calbindin D9k have been evaluated by NMR spectroscopy on the native dicalcium and on the paramagnetic monocerium-substituted derivative. Although at 2 M GdmHCl the ...
Mössbauer Spectral Study of Two Layered Honeycomb Molecular Magnets: PPh4FeIIFeIII(ox)3 and NBu4FeIIFeIII(ox)3
2002
The Mossbauer spectra of the layer ferrimagnets PPh4FeIIFeIII(ox)3 and NBu4FeIIFeIII(ox)3 have been measured between 1.9 and 315 K. The paramagnetic spectra exhibit both high-spin iron(II) and iron(III) doublets. The iron(II) quadrupole splittings are negative and decrease substantially upon cooling as a result of a low-symmetry crystal field splitting. In contrast, the iron(III) splittings are small, positive, and virtually independent of temperature. The respective magnetic ordering temperatures of 30 and 42.5 K agree well with the phase observed by bulk magnetometry and the magnetic sextets yield hyperfine fields of ca. 60 kOe for iron(II) and 540 kOe for iron(III). The unusually low iro…
Giant magnetoresistance in semiconducting DyNiBi
2008
Abstract The semiconducting half-Heulser compound DyNiBi shows a negative giant magnetoresistance (GMR) below 200 K. Except for a weak deviation, this magnetoresistance scales roughly with the square of the magnetization in the paramagnetic state, and is related to the metal–insulator transition. At low temperature, a positive magnetoresistance is found, which can be suppressed by high fields. The magnitude of the positive magnetoresistance changes slightly with the amount of impurity phase.
Magnetic and structural investigations of ultra-thin Co–Fe alloy films on W(1 1 0)
2004
Abstract We investigated ultra-thin CoxFe1−x films on a flat and vicinal BCC W(1 1 0) surface with thicknesses between 1.8 and 7 monolayers (ML) using longitudinal Kerr magnetometry. We found a transition from magnetic bulk behavior between 3 and 4 ML to the monolayer. The maximum of the remnant Kerr signal that appears for thicker films at x=0.5 turns into a minimum for a sample thickness below 4 ML , while the specific Kerr-rotation per monolayer shows the well known bulk behavior. A similar magnetic behavior on the flat as well as on the stepped part of the substrate indicates that this is an intrinsic property. For x=0.5 the pseudomorphic monolayer is paramagnetic even when it is covere…
Correlation of quenched structural disorder and magnetism inTiFe2Laves-phase thin films
2002
In recent bandstructure calculations for the $C14$ Laves-phase intermetallic compound ${\mathrm{TiFe}}_{2}$ two energetically nearly degenerate magnetic ground states (antiferromagnetic and ferromagnetic) were predicted. As a consequence of this near-degeneracy in the $C14$ stability range of ${\mathrm{Ti}}_{x}{\mathrm{Fe}}_{1\ensuremath{-}x}$ $(x\ensuremath{\approx}1/3)$ the magnetic properties are strongly correlated with the sublattices' occupation by Ti and Fe. We analyzed the magnetic properties of a series of thin epitaxial films with varying composition in the $C14$ stability range. The temperature- and field-dependent magnetic properties of these samples were determined by dc superc…