Search results for "C.M.M."
showing 10 items of 1066 documents
Mn(IV) and Co(III)-complexes of –OH-rich ligands possessing O2N, O3N and O4N cores: syntheses, characterization and crystal structures
2003
Mn(IV) and Co(III) complexes of tridentate –OH–rich ligands possessing O2N, O3N and O4N donor sets were synthesized, characterized and their structures were established by single crystal X-ray diffraction, where the binding core is O4N2. In the structurally characterized complexes, the coordination geometry about the metal ion was found to be distorted octahedral.
Support work function as a descriptor and predictor for the charge and morphology of deposited Au nanoparticles.
2020
We show, using density functional theory calculations, that the charge, magnetic moment, and morphology of deposited Au nanoclusters can be tuned widely by doping the oxide support with aliovalent cations and anions. As model systems, we have considered Aun (n = 1, 2, or 20) deposited on doped MgO and MgO/Mo supports. The supports have been substitutionally doped with varying concentrations θ of F, Al, N, Na, or Li. At θ = 2.78%, by varying the dopant species, we are able to tune the charge of the Au monomer between −0.84e and +0.21e, the Au dimer between −0.87e and −0.16e, and, most interestingly, Au20 between −3.97e and +0.49e. These ranges can be further extended by varying θ. These chan…
Al driven peculiarities of local coordination and magnetic properties in single phase Alx CrFeCoNi high entropy alloys
2021
The authors thank the Helmholtz-Zentrum Berlin for the provision of access to synchrotron radiation facilities and allocation of synchrotron radiation at the PM2-VEKMAG, BAMline, and UE46_PGM-1 beamlines of BESSY II at HZB as well as measurement time for magnetometry at HZB CoreLab for Quantum Materials. A. S. acknowledges personal funding from CALIPSOplus project (the Grant Agreement no. 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020). The financial support for the VEKMAG project and the PM2-VEKMAG beamline by the German Federal Ministry for Education and Research (Nos. BMBF 05K10PC2, 05K10WR1, 05K10KE1) and by HZB is cordially acknowledged by all co-author…
Correlation of local disorder and electronic properties in the Heusler alloy Co2Cr0.6Fe0.4Al
2007
For the fully ordered Heusler alloy Co2Cr0.6Fe0.4Al half-metallic ferromagnetism has been predicted. Local disorder other than the Al–Cr/Fe (B2)-type disorder is known to destroy the half-metallic bandgap. The usage of appropriate buffer layers improves the structural quality of thin films. We correlate the structural properties of thin magnetron sputtered films determined by x-ray diffraction with details of the x-ray magnetic circular dichroism spectra. From the value of the magnetic moment located at the Cr atom and features of the Co absorption spectra we conclude that the buffer layers lead also to an improvement in the local atomic order. The atomic ordering gradually approaches the l…
Ionic conduction through single-pore and multipore polymer membranes in aprotic organic electrolytes
2021
Abstract We experimentally characterize the ionic conduction of single and multipore nanoporous membranes in aprotic organic electrolytes. To this end, soft-etched (SE) membranes with pore diameters in the nanometer range and track-etched (TE) membranes with pore diameters in the tens of nanometers range are investigated. In aqueous conditions, the membrane ionic conduction rates follow the same trend of the bulk solution conductivities. However, the ionic transport through the narrow SE-nanopores dramatically decreases in aprotic electrolytes due to the formation of solvated metal cations and their adsorption on the pore surface. The current-voltage recordings of single conical nanopores i…
Coupling of membrane and photocatalytic technologies for selective formation of high added value chemicals
2020
Abstract This review presents a survey of some heterogeneous photocatalytic processes for the synthesis of high-value added compounds carried out in photocatalytic membrane reactors (PMRs). The two technologies can be easily integrated due to the similar conditions at which they usually operate. Furthermore, significant advantages derive from the coupling and in some cases also synergistic effects can be observed. These features have been highlighted for the photocatalytic syntheses reviewed along with engineering and design aspects investigated for some industrially relevant high-value added compounds. Notably, photocatalytic syntheses carried out in PMRs are still rare mainly because inte…
Magnetism of monomer MnO and heterodimer FePt@MnO nanoparticles
2017
We report about the magnetic properties of antiferromagnetic (AF) MnO nanoparticles (NPs) with different sizes (6--19 nm). Using a combination of polarized neutron scattering and magnetometry, we were able to resolve previously observed peculiarities. Magnetometry, on the one hand, reveals a peak in the zero-field-cooled (ZFC) magnetization curves at low temperatures $(\ensuremath{\sim}25$ K) but $no$ feature around the N\'eel temperature at 118 K. On the other hand, polarized neutron scattering shows the expected behavior of the AF order parameter vanishing around 118 K. Moreover, hysteresis curves measured at various temperatures reveal an exchange-bias effect, indicating a coupling of an…
Local structure and magnetization of ferromagnetic Cu-doped ZnO films: No magnetism at the dopant?
2016
Abstract Relationship between magnetism and structure of Cu-doped ZnO was investigated at macroscopic and microscopic levels. Thin Zn1−xCuxO films (x = 0.02, 0.04, 0.07 and 0.10) were prepared by a pulsed laser deposition and characterized via superconducting quantum interference device (SQUID) magnetometry, high-resolution x-ray diffraction, and Cu K-edge and Zn K-edge x-ray absorption, x-ray linear dichroism and x-ray circular magnetic dichroism spectroscopy. Even though the samples exhibit room-temperature ferromagnetism with magnetization that increases with Cu concentration, we did not detect signatures of local magnetic moments associated with Cu atoms, as evidenced by the lack of any…
Electronic and crystallographic structure, hard x-ray photoemission, and mechanical and transport properties of the half-metallic Heusler compound Co…
2011
This work reports on the electronic and crystalline structure and the mechanical, magnetic, and transport properties of the polycrystalline Heusler compound Co${}_{2}$MnGe. The crystalline structure was examined in detail by extended x-ray absorption fine-structure spectroscopy and anomalous x-ray diffraction. The compound exhibits a well-ordered $L{2}_{1}$ structure as is typical for Heusler compounds with 2:1:1 stoichiometry. The low-temperature magnetic moment agrees well with the Slater-Pauling rule and indicates a half-metallic ferromagnetic state of the compound, as is predicted by ab initiocalculations. Transport measurements and hard x-ray photoelectron spectroscopy were performed t…
Electronic Properties of 6H Hexagonal SrMnO3
2015
SrMnO3 ceramic was prepared by conventional high-temperature sintering method. Dielectric studies were performed within the temperature range 125–300 K at the frequency 10–400 kHz. The electronic properties of stoichiometric and oxygen defected SrMnO3 crystal in hexagonal 6H- P63/mmc symmetry at 0 K were calculated in ab initio procedure based on density functional theory using the Spanish Initiative for Electronic Simulations with Thousands of Atoms (SIESTA) code. The lattice parameters and density of states were obtained. The ideal 6H-SrMnO3 crystal has the band gap energy about 0.2–0.3 eV at 0 K. Contribution of an exchange-correlation energy into the total energy is about 32%, a magneti…