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Magnetic Moments (magnetic + moment)
Kinds of Magnetic Moments Selected AbstractsTuning the Magnetic Moment of [Ru2(DPhF)3(O2CMe)L]+ Complexes (DPhF=N,N, -Diphenylformamidinate): A Theoretical Explanation of the Axial Ligand InfluenceCHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2010Carmen Barral Dr. Abstract The magnetic behaviour of the compounds containing the [Ru2(DPhF)3(O2CMe)]+ ion (DPhF,=N,N, -diphenylformamidinate) shows a strong dependence on the nature of the ligand bonded to the axial position. The new complexes [Ru2(DPhF)3(O2CMe)(OPMe3)][BF4],0.5,CH2Cl2 (1, 0.5,CH2Cl2) and [Ru2(DPhF)3(O2CMe)(4-pic)][BF4] (2) (4-pic=4-methylpyridine) clearly display this influence. Complex 1,0.5,CH2Cl2 shows a magnetic moment corresponding to a S=3/2 system affected by the common zero-field splitting (ZFS) and a weak antiferromagnetic interaction, whereas complex 2 displays an intermediate behaviour between S=3/2 and S=1/2 systems. The experimental data of complex 1 are fitted with a model that considers the ZFS effect using the Hamiltonian ,D=S,D,S. The weak antiferromagnetic coupling is introduced as a perturbation, using the molecular field approximation. DFT calculations demonstrate that, in the [Ru2(O2CMe)(DPhF)3(L)]+ complexes, the energy level of the metal,metal molecular orbitals is strongly dependent on the nature of the axial ligand (L). This study reveals that the increase in the ,-acceptor character of L leads to a greater split between the ,* and ,* HOMO orbitals. The influence of the axial ligand in the relative energy between the doublet and quartet states in this type of complexes was also analysed. This study was performed on the new complexes 1,0.5,CH2Cl2 and 2. The previously isolated [Ru2(DPhF)3(O2CMe)(OH2)][BF4],0.5,CH2Cl2 (3, 0.5,CH2Cl2) and [Ru2(DPhF)3(O2CMe)(CO)][BF4],CH2Cl2 (4,CH2Cl2) complexes were also included in this study as representative examples of spin-admixed and low-spin configurations, respectively. The [Ru2(DPhF)3(O2CMe)]+ (5) unit was used as a reference compound. These theoretical studies are in accordance with the different magnetic behaviour experimentally observed. [source] Electronic Manifestation of Cation-Vacancy-Induced Magnetic Moments in a Transparent Oxide Semiconductor: Anatase Nb:TiO2ADVANCED MATERIALS, Issue 22 2009Shixiong Zhang Nb-doped anatase TiO2 thin films grown by pulsed-laser deposition show Kondo scattering in elctronic-transport measurements, providing evidence for the formation of magnetic moments. The origin of magnetism is attributed to cation (Ti) vacancies, confirmed by X-ray absorption spectroscopy and first-principle calculations. The Ti vacancies are controlled by oxygen partial pressure during growth. [source] Magnetic Moments of the Endohedral Cluster Fullerenes Ho3N@C80 and Tb3N@C80: The Role of Ligand Fields.CHEMINFORM, Issue 32 2005Manfred Wolf No abstract is available for this article. [source] In-vitro antimicrobial, thermal and spectral studies of mixed ligand Cu(II) heterochelates of clioquinol and coumarin derivativesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2010G. J. Kharadi Abstract The mixed-ligand heterochelates of Cu(II) with 5-chloro-7-iodo-8-hydroxyquinoline (clioquinol) and various uninegative bidentate ligands were prepared. The structure of mixed-ligand heterochelates was investigated using spectral, physicochemical, elemental analysis and thermal studies. The FAB-mass spectrum of [Cu(A2)(CQ)(H2O)2].2H2O has been carried out. Magnetic moment and reflectance spectral studies reveal that an octahedral geometry has been assigned to all the prepared heterochelates. The kinetic parameters such as order of reaction (n), the energy of activation (Ea), the pre-exponential factor (A), the activation entropy (,S#), the activation enthalpy (,H#) and the free energy of activation (,G#) have been reported. The ligands, metal salts, heterochelates, control and standard drug were tested for their in-vitro antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens and Bacillus substilis. The metal complexes exhibit good activity against bacterial strains compared with parental compounds, and moderate compared with the standard drug (clioquinol). Copyright © 2010 John Wiley & Sons, Ltd. [source] Novel drug-based Fe(III) heterochelates: synthetic, spectroscopic, thermal and in-vitro antibacterial significanceAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2010D.H. Jani Abstract A series of novel heterochelates of the type [Fe(An)(L)(H2O)2],mH2O [where H2An = 4,4,-(arylmethylene)bis(3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-ol); aryl = 4-nitrophenyl, m = 1 (H2A1); 4-chlorophenyl, m = 2 (H2A2); phenyl, m = 2 (H2A3); 4-hydroxyphenyl, m = 2 (H2A4); 4-methoxyphenyl, m = 2 (H2A5); 4-hydroxy-3-methoxyphenyl, m = 1.5 (H2A6); 2-nitrophenyl, m = 1.5 (H2A7); 3-nitrophenyl, m = 0.5 (H2A8); p -tolyl, m = 1 (H2A9) and HL = 1-cyclopropyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid] were investigated. They were characterized by elemental analysis (FT-IR, 1H- & 13C-NMR, and electronic) spectra, magnetic measurements and thermal studies. The FAB-mass spectrum of [Fe(A3)(L)(H2O)2],2H2O was determined. Magnetic moment and reflectance spectral studies revealed that an octahedral geometry could be assigned to all the prepared heterochelates. Ligands (H2An) and their heterochelates were screened for their in-vitro antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Serratia marcescens bacterial strains. The kinetic parameters such as order of reaction (n), the energy of activation (Ea), the pre-exponential factor (A), the activation entropy (,S#), the activation enthalpy (,H#) and the free energy of activation (,G#) are reported. Copyright © 2009 John Wiley & Sons, Ltd. [source] Nuclear magnetic moments from NMR spectra,Experimental gas phase studies and nuclear shielding calculationsCONCEPTS IN MAGNETIC RESONANCE, Issue 5 2007Karol Jackowski Abstract NMR spectra of gaseous compounds and quantum chemical calculations are combined to determine new accurate values of magnetic dipole moments for a series of nuclei. We have analyzed shielding constants, resonance frequencies, and nuclear magnetic moments for a group of simple molecules. The chemical shifts and resonance frequencies are measured at 300 K and extrapolated to the zero-density limit in order to remove all the intermolecular effects from the experimental parameters. The absolute shielding constants in the studied molecules are obtained from ab initio calculations. Assuming the proton magnetic moment as the reference, we determine the nuclear magnetic moments of 13C, 14N, 15N, 17O, 19F, 29Si, 31P, 33S, and 73Ge. The new nuclear magnetic moments are consistent with the experimental NMR parameters, and using these new values one can for the first time predict successfully the shielding constant of a nucleus in a molecule when the corresponding resonance frequency is known. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 246,260, 2007. [source] Supercritical-Fluid-Assisted One-Pot Synthesis of Biocompatible Core(, -Fe2O3)/Shell(SiO2) Nanoparticles as High Relaxivity T2 -Contrast Agents for Magnetic Resonance ImagingADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Elena Taboada Abstract Monodisperse iron oxide/microporous silica core/shell composite nanoparticles, core(, -Fe2O3)/shell(SiO2), with a diameter of approximately 100,nm and a high magnetization are synthesized by combining sol,gel chemistry and supercritical fluid technology. This one-step processing method, which is easily scalable, allows quick fabrication of materials with controlled properties and in high yield. The particles have a specific magnetic moment (per kg of iron) comparable to that of the bulk maghemite and show superparamagnetic behavior at room temperature. The nanocomposites are proven to be useful as T2 MRI imaging agent. They also have potential to be used in NMR proximity sensing, theranostic drug delivery, and bioseparation. [source] Measuring remanence anisotropy of hematite in red beds: anisotropy of high-field isothermal remanence magnetization (hf-AIR)GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2009Dario Bilardello SUMMARY The potential of using high-field anisotropy of isothermal remanence magnetization (hf-AIR) measurements for determining the origin of natural remanent magnetization in red beds and for identifying and correcting possible red-bed inclination shallowing was investigated for specimens of the Carboniferous Shepody Formation of New Brunswick and Nova Scotia, Canada. The technique makes it possible for a typical paleomagnetic laboratory to measure the remanence anisotropy of high-coercivity hematite. High-field (hf) AIR was used in conjunction with 100 mT alternating field (af) and 120 °C thermal demagnetization to separate the contribution of hematite to the remanence anisotropy from that of magnetite/maghemite and goethite, respectively. A 5-T impulse DC magnetic field was used for the hf-AIR to reset the magnetic moment of high-coercivity hematite so that demagnetization between AIR orientations was not necessary. The ability of a 5-T field to reset the magnetization was tested by generating an isothermal remanent magnetization acquisition curve for hematite by using impulse DC magnetic fields up to 5 T in one orientation and followed by applying a field in the opposite direction at each step. Each field application was treated by 120 °C heating and 100 mT af demagnetization before measurement. At 5 T, the difference between the magnetizations applied in opposite directions disappeared indicating that no magnetic memory persisted at this field strength. We performed a validity and reproducibility test of our hf-AIR measurement technique by measuring three specimens multiple times along two orthogonal coordinate systems. The method yielded highly reproducible results and, on rotating the specimen's coordinates, the fabric rotated by 90° as expected, showing that it is not an artifact of the technique. We also measured hf-AIR on samples that had previously been chemically demagnetized in 3N HCl to remove the secondary, chemically grown pigmentary hematite. The hf-AIR fabric of leached samples is similar to that of untreated samples, but shows a better-defined magnetic lineation and imbrication. We interpret the fabric observed for the Shepody Formation to be a compactional fabric that has been reoriented by strain during folding following a flexural-slip model. [source] Half metallic properties of LaSrVMoO6JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 9 2010Weiyu Song Abstract The recent synthesized LaSrVMoO6 was speculated to be compensated half metal, i.e., half metal with zero magnetic moment. Based on the experimental structure, our first principles study indicates that it is ferrimagnetic and half metallic with the magnetic moment 2.0 ,B when the electron correlation of Mo 4d electrons is larger than 2.72 eV. This indicates the strong electron correlation effect of Mo 4d electrons. Nonetheless, the obtained large magnetic moment (2.0 ,B) contradicts with the experimental observed nearly zero magnetic moment. Although the large antisite defects of the experimental sample might be the reason to reduce the saturated magnetic moment, further physical insights need to be investigated. The spin-orbit coupling effect has minor effect on the studied properties. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] Complexes of Co(II) and Zn(II) with ofloxacin.JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2002Crystal structure of [Co(oflo)2(MeOH)2]·4MeOH Abstract Ofloxacin (oflo) is able to interact with Co(II) and Zn(II) salts to form complexes with the general formula [M(oflo)2],·,4H2O, (M,=,Co, Zn). Bonding takes place through one of the oxygen atoms of the carboxylate group (acting as a monodentate) and the oxygen atom of the ketonic group. The IR bands of the carboxylic and ketonic group at 1713 and 1622 cm,1, respectively, shift to 1615 and 1575 cm,1 in the complexes. After dissolution in methanol, complex [Co(oflo)2],·,4H2O crystallizes as [Co(oflo)2(MeOH)2],·,4MeOH, where Co(II) ion is in an octahedral environment of oxygen atoms. This compound crystallizes in the triclinic system, spatial group P-1, with unit cell dimensions a,=,9.3670(12), b,=,11.4135(17), c,=,11.851(2) Ĺ y ,,=,71.999(14), ,,=,73.698(12), ,,=,83.528(14)°. Magnetic properties (effective magnetic moment 5.02 BM) and visible spectrum (bands at 490, 510, and 1152 nm) are characteristic of such an octahedral geometry. 1H- and 13C-NMR spectra of the Zn(II) complex indicate only small structural changes in ofloxacin upon coordination to the metallic site. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:2416,2423, 2002 [source] Multiferroic Properties of Nanocrystalline PbTiO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2010Min Wang Nanocrystalline PbTiO3 (PTO) powders in a perovskite structure have been synthesized by the sol,gel process using lead acetate, glycerin, and titanium (IV) isopropoxide as precursors. PTO ceramics were obtained by sintering the powders at temperatures ranging from 600° to 1000°C. The structure and morphology of the ceramics have been determined by X-ray diffraction, transmission electron microscopy, and field emission scanning electron microscopy. The PTO powder calcined at 450°C shows weak ferromagnetism at room temperature. The PTO ceramics sintered at various temperatures exhibit coexistence of ferroelectricity and weak ferromagnetism at room temperature. Enhancement in the magnetic moment and ferroelectricity with a reduction in the grain size of PTO ceramics was observed. This result facilitates the possibilities of new perovskite electromagnetic devices at the nanoscale level. [source] Hyperfine structure of hydrogen and geoniumLASER PHYSICS LETTERS, Issue 2 2004A.V. Andreev Abstract The self-consistent theory of hyperfine atomic structure is developed. The theory is based on Lorentz and gauge invariant equation for action of spin 1/2 particle. The specific feature of proposed equation for action (or Lagrangian) is that it is enable to introduce the three material constants: mass m0, charge q, and magneton (i.e. magnitude of magnetic moment) ,. The analytically tractable solutions of the wave equation for the electron motion in Coulomb field and electron motion in uniform magnetic field are found. In both cases the calculated spectra include the hyperfine splitting that is agreed well with the experimentally observed spectra. The calculated frequencies of 8(12)d3/2 , 8(12)d5/2 transitions in hydrogen atom are compared with the results of experimental measurements by the highprecision spectroscopy methods. It is shown that the results of calculations are in good agreement with the experimentally measured data. (© 2004 by HMS Consultants. Inc. Published exclusively by WILEY-VCH Verlag GmbH & Co.KGaA) [source] The dressed nonrelativistic electron in a magnetic fieldMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 10 2006Laurent Amour Abstract We consider a nonrelativistic electron interacting with a classical magnetic field pointing along the x3 -axis and with a quantized electromagnetic field. When the interaction between the electron and photons is turned off, the electronic system is assumed to have a ground state of finite multiplicity. Because of the translation invariance along the x3 -axis, we consider the reduced Hamiltonian associated with the total momentum along the x3 -axis and, after introducing an ultraviolet cutoff and an infrared regularization, we prove that the reduced Hamiltonian has a ground state if the coupling constant and the total momentum along the x3 -axis are sufficiently small. We determine the absolutely continuous spectrum of the reduced Hamiltonian and, when the ground state is simple, we prove that the renormalized mass of the dressed electron is greater than or equal to its bare one. We then deduce that the anomalous magnetic moment of the dressed electron is nonnegative. Copyright © 2006 John Wiley & Sons, Ltd. [source] Accreting millisecond pulsar SAX J1808.4,3658 during its 2002 outburst: evidence for a receding discMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2009Askar Ibragimov ABSTRACT An outburst of the accreting X-ray millisecond pulsar SAX J1808.4,3658 in 2002 October,November was followed by the Rossi X-ray Timing Explorer for more than a month. A detailed analysis of this unprecedented data set is presented. For the first time, we demonstrate how the area covered by the hotspot at the neutron star surface is decreasing in the course of the outburst together with the reflection amplitude. These trends are in agreement with the natural scenario, where the disc inner edge is receding from the neutron star as the mass accretion rate drops. These findings are further supported by the variations of the pulse profiles, which clearly show the presence of the secondary maximum at the late stages of the outburst after October 29. This fact can be interpreted as the disc receding sufficiently far from the neutron star to open the view of the lower magnetic pole. In that case, the disc inner radius can be estimated. Assuming that disc is truncated at the Alfvén radius, we constrain the stellar magnetic moment to ,= (9 ± 5) × 1025 G cm3, which corresponds to the surface field of about 108 G. On the other hand, using the magnetic moment recently obtained from the observed pulsar spin-down rate we show that the disc edge has to be within factor of 2 of the Alfvén radius, putting interesting constraints on the models of the disc,magnetosphere interaction. We also demonstrate that the sharp changes in the phase of the fundamental are intimately related to the variations of the pulse profile, which we associate with the varying obscuration of the antipodal spot. Using the phase-resolved spectra, we further argue that the strong dependence of the pulse profiles on photon energy and the observed soft time lags result from the different phase dependence of the normalizations of the two spectral components, the blackbody and the Comptonized tail, being consistent with the model, where these components have significantly different angular emission patterns. The pulse profile amplitude allows us to estimate the colatitude of the hotspot centroid to be ,4°,10°. [source] Half-metallicity and magnetism at Heusler alloy surfaces: Co2MSi(001) (M = Ti, Cr)PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2008Ying Jiu Jin Abstract We investigated the electronic structures, magnetism, and half-metallicity at the (001) surfaces of full-Heusler alloys, Co2MSi (M = Ti, Cr), by using the all-electron full-potential linearized augmented plane wave method within the generalized gradient approximation. Both the Co-terminated (Co-term) and the MSi-terminated (MSi-term) surfaces were considered. From the calculated atom-resolved density of states, we found that the half-metallicity was destroyed at the Co-term surfaces for both alloys. The electronic structures at the MSi-term surfaces of the two alloys showed much different behavior. The half-metallicity was retained at the TiSi-term for Co2TiSi(001) but the minority spin gap was much reduced due to surface states located just below the Fermi level. On the other hand the half-metallicity was destroyed at the CrSi-term of Co2CrSi(001) due to the surface states located at the Fermi level. The calculated magnetic moment of the surface Co atom of the Co-term for Co2CrSi(001) was increased slightly to 1.05,B with respect to that of the deep inner layers (,1.00,B), while that for Co2TiSi(001) was decreased to 0.88,B. Large enhancement of the magnetic moment was found for the surface Ti atoms at TiSi-term of Co2TiSi(001) and Cr atoms at CrSi-term of Co2CrSi(001) with values of 0.07,B and 2.91(B, respectively. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Magnetic study of Hitperm alloys (Fe0.5Co0.5)1,x ,y ,zMxByCuz (M = Hf, Zr, Nb)PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2006Abstract A family of the Hitperm alloys (Fe0.5Co0.5)1,x ,y ,zMxByCuz (M = Hf, Zr, Nb) produced in an argon atmosphere as amorphous ribbons with 0.025 mm thickness are investigated up to 1200 K. The partial replacement of Fe by Co with optimal Fe0.5Co0.5 ratio increases the Curie temperature of the amorphous phase and the magnetic moment per formula unit. The early stages of crystallization can be observed by magnetization measurements. Alloys subjected to the first controlled crystallization stage are built of bcc-(Fe,Co) nanocrystals that are homegeneously embedded in the amorphous matrix. Mean grain sizes are about 11 nm. These two-phase alloys exhibit good soft magnetic properties with the relatively low coercive fields up to 50 A/m. Hafnium and hafnium/zirconium mixture are found to be the best inhibitors of the nanograin growth resulting in the best soft magnetic parameters. Alloys with niobium exhibit lower thermal stability and higher coercive fields. The correlation between the structure evolution and the magnetic properties is analysed and discussed. Conditions for optimum heat treatment are also determined. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Change in the magnetic properties of [FeII(phen)3](PF6)2 in the solid state by combining grinding and annealingPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2004T. Ohshita Abstract By grinding crystalline [FeII(phen)3](PF6)2, the effective magnetic moment, or ,MT, increased with simultaneous amorphization. Subsequent annealing further increased ,MT, despite the restoration of the crystallinity. This was explained by the recovery of the counterion, PF6,, from its strained state in the intact crystal to a less strained state towards higher spherical symmetry. The effects of annealing preceded by grinding suggest a novel method to control the magnetic states of coordination compounds without regard to their crystalline states. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Experimental and theoretical study of the magnetic properties and XMCD spectra of Ru clusters deposited on Fe/Cu(001)PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2010J. Minár Abstract We present results of an experimental study of magnetic properties of small Ru clusters deposited on a thin Fe film grown on Cu(001) surface. X-ray magnetic circular dichroism (XMCD) measurements show finite spin and orbital moments of Ru dimers and trimers, however a magnetic moment for a Ru monomer has been not observed. A corresponding theoretical study based on the fully relativistic multiple scattering KKR method is presented. Detailed theoretical analysis has been performed to explain the experimental findings. In particular a direct comparison of the calculated XMCD with the experiments suggests diffusion into the surface as a possible reason for the apparent quenching of the spin magnetic moment for Ru monomers. [source] Electronic structure and magnetic properties of Cu-doped SnO2 from first-principles studyPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2009Chang-wen Zhang Abstract We have studied the electronic structure of Cu-doped SnO2, with different possible geometrical sites for the Cu dopant, to determine the most favored magnetic properties. Our study shows that each Cu has spin-polarized states in the band gap generating a magnetic moment 2.0,B. We also find Cu impurities tend to form clusters which induces strong ferromagnetism with high Curie temperature, through the same p,d hopping interactions as found in Sr2FeMoO6 [Phys. Rev. Lett. 85, 2549 (2000)]. Doped p-type carriers enhanced the ferromagnetism, while n-type carriers are detrimental to ferromagnetism due to charge compensating effects, indicating that the strong ferromagnetism in Cu-doped SnO2 would be achieved by hole doping. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Excitons in motion: universal dependence of the magnetic moment on kinetic energyPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2008V. P. Kochereshko Abstract We have observed remarkable changes in the magnetic properties of excitons as they acquire kinetic energy. In particular, the Zeeman splittings and diamagnetic shifts of excitonic transitions when magnetic fields are applied along the growth direction of (001) wide quantum wells of CdTe, ZnSe, ZnTe and GaAs are found to to have a strong dependence on the translational wavevector Kz. The behaviour of the Zee-man splittings corresponds to enhancement of the magnetic moments of the excitons. This enhancement is particularly marked when their translational kinetic energy becomes comparable with the exciton Rydberg and can be described by what appears to be a universal function of Kz. A model for the behaviour is outlined which involves motionally-induced mixing between the 1S hydrogenic exciton ground state and excited nP states. The observations imply that there are significant changes in the structure of the exciton as its translational kinetic energy increases. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Half-metallic ferromagnetism in wurtzite SrCPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2008Chang-wen Zhang Abstract The first-principles full potential linearized augmented plane-wave method within density-functional theory is used to investigate electronic structure and magnetism of wurtzite (WZ) crystal structure SrC. It is shown that the WZ SrC is a true half-metallic ferromagnet with a magnetic moment of 2,B per formula unit. The large HM gaps (0.72 eV) and robustness of half-metallicity with respect to the lattice change make it possible candidate grown epitaxially on appropriate substrates in the form of films thick enough, and therefore should be useful in spintronics and other related applications. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Antiferromagnetic-to-ferromagnetic transition induced by aluminum in the Ti(Fe1,xAlx)2 intermetallic compounds: a 57Fe Mössbauer spectroscopy studyPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2007N. N. Delyagin Abstract Mössbauer spectroscopy has been used to investigate the hyperfine field distributions and the local spin configurations of Fe atoms in the magnetically ordered Ti(Fe1,xAlx)2 compounds. The evolution of the spin arrangement of the Fe atoms was observed over the concentration range 0 , x , 0.25 at 5 K. The Al impurity suppresses the ferromagnetic exchange in the Fe(6h) layers and simultaneously provides the conditions for a transition of the Fe(2a) atoms, which are nonmagnetic in the TiFe2 compound, to the states with nonzero magnetic moment. The magnetic behavior of the Fe(2a) atoms is the key factor governing the anti- to ferromagnetic transition in the Ti(Fe1,xAlx)2 compounds. The magnetic ordering temperatures of the Ti(Fe1,xAlx)2 compounds were determined. In addition, the parameters of the electric-field gradient in TiFe2 as well as the relationship between the value of the magnetic moment of the Fe atom and the type of atomic configuration were discussed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Growth and magnetic properties of Mn-doped ZnSiAs2/Si heterostructuresPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2009Aleksey Kochura Abstract Mn-doped ZnSiAs2/Si heterostructures were grown by vacuum-thermal deposition of ZnAs2 and Mn layers on Si substrates followed by annealing. The surface contained a ZnSiAs2 film, but also micro-crystals with a composition close to ZnAs2 or ZnSiAs2 -Si-SiAs eutectic. The temperature and field dependencies of the magnetization were measured. Two types of magnetic phases were detected: a paramagnetic one with the mean magnetic moment of 7.6 Bohr magnetons, formed by Mn2+ ions, and a ferromagnetic one with Curie temperature 340 K in 50 kOe magnetic field, formed by MnAs clusters. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Increase of the Zeeman splitting of excitonic-polaritons due to their motionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2005V.P. Kochereshko Abstract Reflectivity spectra from GaAs and CdTe based wide quantum wells (widths L = 50,1000 nm) have been studied in magnetic fields in Faraday geometry. The magnitude of the exciton Zeeman splitting has been found to grow with increase of the quantization index N for the exciton energy levels. Since N is related to the magnitude of the exciton wave vector K, the observed effect means that the magnetic moment of the exciton gets larger as the kinetic energy increases. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Magnetic properties of bimetallic Co-Pd nanostructuresPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2005Javier Guevara Abstract We study the dependence of the magnetic properties of Co-Pd nanoclusters (Co cores coated by Pd atoms) on size and relative composition. We consider Co-Pd clusters having closed shell cubo-octahedral structure with an increasing Co core size. The electronic and magnetic properties are calculated with a parametrized Hubbard Hamiltonian within the unrestricted Hartree-Fock approximation. We show that, depending on the relative composition, the Pd coating can give rise to an enhancement of the average magnetic moment of the Co core. We compare with results from slabs by using an ab initio calculation method. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] EPR studies on Na-oleate coated Fe3O4 nanoparticlesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2004Y. Köseo Abstract Superparamagnetic iron oxide nanoparticles were prepared by the co-precipitation technique. Then, fine iron oxide nanoparticles were coated by Na-oleate. Magnetic properties of Na-oleate coated and uncoated iron oxide nanoparticles were investigated by Electron Paramagnetic Resonance (EPR) technique. At room temperature, a single, strong and broad EPR signal was observed for both samples with effective g-values of 2,0839 and 2,18838 for coated and uncoated samples, respectively. The intensity, line width and the resonance field for both coated and uncoated samples are strongly temperature dependent. When the sample is coated with Na-oleate, the line width and the resonance field values of the EPR signal increase due to the decrease in the magnetic interaction between the particles. The total effective magnetic moment of such coated particles is found to decrease, which is most likely due to a non-collinear spin structure originated from the pinning of the surface spins and coated surfactant at the interface of nanoparticles. [source] Magnetic properties of ultra-thin epitaxial V/Gd bilayersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2004P. Pankowski Abstract Magnetic properties of a new system of epitaxial vanadium/gadolinium bilayers with different V thickness have been studied. The structure and quality of bilayers was determined by X-ray reflectivity measurements using synchrotron radiation. Hysteresis loops measurements suggest in-plane anisotropy for all samples (Mr/Ms close to 1). Basic magnetic properties: saturation magnetisation, coercive field and remanence were obtained. Average magnetic moment analysis gives a possibility of an induced magnetic moment on vanadium atoms. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Change in electronic structure in a six-coordinate copper(II) complex accompanied by an anion order/disorder transitionACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2010Colin A. Kilner A variable-temperature crystallographic study of [Cu(LOH)2][ClO4]2·2(CH3)2CO [LOH = 2,6-bis(hydroxyiminomethyl)pyridine] between 30 and 300,K is presented. The complex exhibits an unusual electronic structure at room temperature with a {}1 ground state, corresponding to an axially compressed ligand coordination geometry about the copper ion. This reflects a suppression of the pseudo-Jahn,Teller distortion that is normally shown by copper(II) compounds with this ligand geometry [Halcrow et al. (2004). New J. Chem.28, 228,233]. On cooling the compound undergoes an abrupt structural change at 157,±,3,K, that does not involve a change in the space group (P), but causes significant changes to c and the unit-cell angles. This reflects a conformational rearrangement of the complex dication, towards a more typical pseudo-Jahn,Teller elongated coordination geometry. This occurs concurrently with a crystallographic ordering of one of the two perchlorate anions, and a significant displacement of the two lattice acetone molecules. The transformation involves displacements of up to 0.5,Ĺ in the non-H atoms of the structure at 30,K, compared with their positions at 300,K. The change in coordination geometry of the complex around 157,K is reflected in a small reduction in its magnetic moment near that temperature. [source] Magnetic behaviour of synthetic Co2SiO4ACTA CRYSTALLOGRAPHICA SECTION B, Issue 6 2009Andrew Sazonov Synthetic Co2SiO4 crystallizes in the olivine structure (space group ) with two crystallographically non-equivalent Co positions and shows antiferromagnetic ordering below 50,K. We have investigated the temperature variation of the Co2SiO4 magnetic structure by means of non-polarized and polarized neutron diffraction for single crystals. Measurements with non-polarized neutrons were made at 2.5,K (below TN), whereas polarized neutron diffraction experiments were carried out at 70 and 150,K (above TN) in an external magnetic field of 7,T parallel to the b axis. Additional accurate non-polarized powder diffraction studies were performed in a broad temperature range from 5 to 500,K with small temperature increments. Detailed symmetry analysis of the Co2SiO4 magnetic structure shows that it corresponds to the magnetic (Shubnikov) group Pnma, which allows the antiferromagnetic configuration (Gx, Cy, Az) for the 4a site with inversion symmetry (Co1 position) and (0,Cy,0) for the 4c site with mirror symmetry m (Co2 position). The temperature dependence of the Co1 and Co2 magnetic moments obtained from neutron diffraction experiments was fitted in a modified molecular-field model. The polarized neutron study of the magnetization induced by an applied field shows a non-negligible amount of magnetic moment on the oxygen positions, indicating a delocalization of the magnetic moment from Co towards neighbouring O owing to superexchange coupling. The relative strength of the exchange interactions is discussed based on the non-polarized and polarized neutron data. [source] Microwave-assisted synthesis, spectroscopy and biological aspects of binuclear titanocene chelates of isatin-2,3-bis(thiosemicarbazones)APPLIED ORGANOMETALLIC CHEMISTRY, Issue 1 2009Priyanka Banerjee Abstract The reactions of bis(cyclopentadienyl)titanium(IV) chloride with a new class of bis(thiosemicarbazones) (H2L), derived by condensing isatin with different N(4)-substituted thiosemicarbazides, have been studied both by a conventional stirring method and also using microwave technology. Binuclear products of type [{(,5 -C5H5)2TiCl} 2(L)] have been isolated in both cases. Tentative structural conclusions are drawn for the reaction products based upon analysis, electrical conductance, magnetic moment and spectral (UV-visible, IR, 1H NMR and 13C NMR) data. FAB mass spectra of these compounds were also recorded to confirm the binuclear structures. Studies were conducted to assess the growth inhibiting potential of the ligands and complexes against various fungal, viral and bacterial strains. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||