Search results for "Susceptibility"
showing 10 items of 912 documents
Guest Removal and External Pressure Variation Induce Spin Crossover in Halogen-Functionalized 2-D Hofmann Frameworks.
2020
The effect of halogen functionalization on the spin crossover (SCO) properties of a family of 2-D Hofmann framework materials, [FeIIPd(CN)4(thioX)2]·2H2O (X = Cl and Br; thioCl = (E)-1-(5-chlorothiophen-2-yl)-N-(4H-1,2,4-triazol-4-yl)methanimine) and thioBr = (E)-1-(5-bromothiophen-2-yl)-N-(4H-1,2,4-triazol-4-yl)methanimine)), is reported. Inclusion of both the chloro- and bromo-functionalized ligands into the Hofmann-type frameworks (1Cl·2H2O and 2Br·2H2O) results in a blocking of spin-state transitions due to internal chemical pressure effects derived by the collective steric bulk of the halogen atoms and guest molecules. Cooperative one-step SCO transitions are revealed by either guest r…
Ligand substitution in cis-bis(acetonitrile)tetrachlororhenium(IV) complex with N,N-dimethylformamide and N,N-dimethylacetamide
2018
Abstract The preparation, crystal structures, and magnetic properties of two novel mononuclear ReIV complexes of formula cis-[ReIVCl4(dmf)2] (1) and cis-[ReIVCl4(dma)2] (2) (dmf = N,N-dimethylformamide and dma = N,N-dimethylacetamide) have been studied. Both ReIV systems were synthesized through ligand substitution reactions from the cis-[ReIVCl4(MeCN)2] precursor, upon heating in the employed solvent. 1 and 2 crystallize in the monoclinic crystal system with space group C2/c. Each ReIV ion exhibits a distorted octahedral environment, being bonded by two oxygen atoms from two dmf (1) and dma (2) molecules and four chloride ions. In the crystal lattice of 1 and 2, the mononuclear ReIV comple…
DNA cleavage reaction induced by dimeric copper(II) complexes of N-substituted thiazole sulfonamides
2005
A new dinuclear copper(II) complex has been synthesised and structurally characterised: [Cu2(tz-ben)4] (Htz-ben = N-thiazol-2-yl-benzenesulfonamide). Its crystal structure, magnetic properties and electronic paramagnetic resonance (EPR) spectra were studied in detail. In the compound the metal centres are bridged by four non-linear triatomic NCN groups. The coordination geometry of the copper ions in the dinuclear entity is distorted square pyramidal (4+1). Two thiazole N and two sulfonamido N atoms occupy the equatorial positions and one sulfonamido O atom is in the axial position. Magnetic susceptibility data show a strong antiferromagnetic coupling, -2J = 114.1 cm(-1). The EPR spectra of…
Polymer-matrix route to (Bi, Pb)2Sr2Ca2Cu3O10+δ: The role of Ca2CuO3☆
1993
Abstract The use of polyethylenimine as active matrix agent has provided a fast synthesis method for (Bi, Pb)2Sr2Ca2Cu3O10+δ, starting from aqueous acetic solutions combined with careful control of the procedural variables. The 110 K phase is obtained as the only superconducting phase after sintering in air during 42 h at 860°C. This technique yields homogeneously sized, large (ca. 20 μm) platelets of the superconducting material. The presence of an excess of calcium and copper over the stoichiometric requirements accelerates the formation of the superconducting phase. This excess, which appears in the resulting material as Ca2CuO3, influences the superconducting properties, other than Tc, …
Antiferromagnetism and the node structure of the superconducting order parameter of UPd Al
2000
The node structure of the superconducting order parameter of the heavy-fermion system is analyzed within the weak-coupling theory. A pairing interaction induced by the exchange of antiferromagnetic spin excitations is assumed as suggested by recent inelastic neutron scattering experiments and tunneling spectroscopy. The multi-sheeted Fermi surface is taken into account. Based on a model susceptibility for the simple antiferromagnetic structure of , line nodes result at the rim of the magnetic Brillouin zone.
Cluster superconductivity in the magnetoelectric Pb(Fe1/2Sb1/2)O3 ceramics
2016
We report the observation of cluster (local) superconductivity in the magnetoelectric Pb(Fe1/2Sb1/2)O3 ceramics prepared at a hydrostatic pressure of 6 GPa and temperatures 1200-1800 K to stabilize the perovskite phase. The superconductivity is manifested by an abrupt drop of the magnetic susceptibility at the critical temperature TC 7 K. Both the magnitude of this drop and TC decrease with magnetic field increase. Similarly, the low-field paramagnetic absorption measured by EPR spectrometer drops significantly below TC as well. The observed effects and their critical magnetic field dependence are interpreted as manifestation of the superconductivity and Meissner effect in metallic Pb nanoc…
Superconductivity in Nb21S8, a Phase with Metal Cluster Chains
1998
Phase pure samples of Nb21S8 are obtained by chemical transport and molten flux reactions in sealed niobium containers at 850−950 °C. In the temperature range from 5 to 290 K the electrical conductivity is found to be moderate metallic with a specific resistivity of 3.90 mΩ cm at 273 K. Magnetic susceptibility measurements give weak, almost temperature independent paramagnetism above ∼40 K. These metallic properties are compared with the structure of Nb21S8, which contains linear single and double chains of fused body centered niobium cubes, separated by S and additional Nb atoms. Both physical measurements consistently show a transition into the superconducting state below 4.1(5) and 3.7(2…
A novel paramagnetic molecular superconductor formed by bis(ethylenedithio)tetrathiafulvalene, tris(oxalato)ferrate(iii) anions and bromobenzene as g…
2005
The new paramagnetic molecular superconductor ET4[(H3O)Fe(C2O4)3]·C6H5Br (1) (Tc = 4.0 K) contains layers of superconducting ET donors alternating with paramagnetic hexagonal layers formed by (H3O)+, [Fe(C2O4)3]3− and guest C6H5Br molecules located in the hexagonal cavities. Conductivity measurements show metallic behavior from room temperature with a minimum in the resistivity at ca. 50 K followed by a smooth increase and a sharp drop in the resistivity with an onset at 4.0 K and a zero resistance at ca. 1.0 K. Magnetoresistance measurements indicate that Hc1 is about 7 mT and that Hc2 is very anisotropic (Hc2⊥ ≥ 5.5 T and Hc2|| ≈ 0.5 T). Magnetic susceptibility measurements show the expec…
Preparation and characterization of (Hg0.7Mo0.3)Sr2(Ca0.7Y0.3)Cu2Ox and (Hg0.9Re0.1)Ba2CaCu2Oy superconducting films by laser ablation
2000
Abstract Oriented (Hg 0.7 Mo 0.3 )Sr 2 (Ca 0.7 Y 0.3 )Cu 2 O x and (Hg 0.9 Re 0.1 )Ba 2 CaCu 2 O y superconducting films were prepared on SrTiO 3 substrates using laser ablation and post-Hg-vapor annealing. Due to the stability of Mo 0.3 Sr 2 (Ca 0.7 Y 0.3 )Cu 2 O x and Re 0.1 Ba 2 CaCu 2 O y in air, no special handling was needed during the grinding, mixing and pressing of the precursor targets. The superconductivity of the films was characterized with the temperature dependence of the ac susceptibility ( χ - T ) and the resistance ( R - T ) while the crystallography was probed with x-ray diffraction (XRD) and scanning electron microscopy (SEM).
Preparation, scaling behavior of activation energy, Hall effect, and flux-flow anisotropy of (Hg0.9Re0.1)Ba2CaCu2O6+δHTS thin films
2004
Abstract We have prepared fully textured (Hg0.9Re0.1)Ba2CaCu2O6+δ (HgRe-1212) thin films by pulsed laser deposition (PLD) and post-annealing. The films exhibit sharp superconducting transitions at Tc=124 K with transition width ΔTc≃2 K. Conditions for reproducible film preparation have been found. The resistive transitions have been investigated in magnetic fields up to 8 T (parallel to the c-axis) and 10 T (perpendicular to the c-axis). We have determined the activation energy of thermally activated flux-motion for both magnetic field orientations. The Hall resistivity (ρxy) of HgRe-1212 superconductor thin films has been measured in the ab-plane at 8 T. In the mixed state a power-law beha…