Value Of Magnetic Moment Research Articles

Effect of the Encapsulation of M (M=Cs, Li and Na) Atom on Spin Dependent Transport of C60 Cage

Using the nonequilibrium Green's function approach (NEGF), the spin-dependent carrier transport is investigated in a molecular junction consisting of a molecule coupled to two semi-infinite single wall carbon nanotubes (SWCNT) leads. The effects of the M atom position and type and the contacts type have been considered on charge current, the maximum value of magnetic moment and the spin polarization. The results indicate that the molecule becomes magnetic by the encapsulating of M atom. Beside, the maximum values of magnetic moment can reach about and the spin polarization can reaches as high as about 95%. The calculated results can be important for application in spintronic.

The coherent potential approximation for strongly correlated systems: electronic structure and magnetic properties of NiO–ZnO solid solutions

A method of electronic structure calculations for strongly correlated disordered materials is developed employing the basic idea of the coherent potential approximation. The evolution of the electronic structure and spin magnetic moment value with the concentration x in strongly correlated Ni1−xZnxO solid solutions is investigated in the framework of this method. The values of the energy gap and magnetic moment obtained are in agreement with the available experimental data.

Bulk and nanocrystalline electron doped Gd0.15Ca0.85MnO3: Synthesis and magnetic characterization

Polycrystalline Gd0.15Ca0.85MnO3 sample was prepared by solid state reaction method and nanocrystalline samples of different grain sizes of the same were prepared by sol–gel method. Phase purity and composition were verified by room temperature X-ray diffraction and SEM-EDAX analysis. Magnetization data of bulk Gd0.15Ca0.85MnO3 in 5kOe field shows a peak at ~119K (TN) suggesting an antiferromagnetic transition. Nanocrystalline Gd0.15Ca0.85MnO3 sample (~54nm size) also shows a cusp at ~107K and a broad thermal hysteresis between field cooled cooling (FCC) and field cooled warming (FCW) data around this temperature. This thermal hysteresis suggests possible crystal structural transition. Field variation of magnetization of bulk Gd0.15Ca0.85MnO3 at 5K shows a tendency to saturate, but yields a magnetic moment value of only ~1.12μB/f.u. in 70kOe. The value of magnetization of nanocrystalline sample at 5K in 70kOe field is slightly larger and is ~1.38μB/f.u. which is probably due to the surface moments of the nanoparticle samples. Both the samples show Curie–Weiss-like behaviour in their paramagnetic state.

Bimetallic thiocyanate bridged Co(II)–Hg(II) polymers with pyrazole and imidazole ligands

In the case of two simple Co(II)–Hg(II) thiocyanate bridged polymers, synthesized in self-assembly processes, we report an interesting example of the magnetic properties of Co(II) complexes. The magnetic susceptibility measurements revealed paramagnetic behavior with negative values of the Curie–Weiss temperature. The larger values of the effective magnetic moment of 4.92μB/f.u. compared to the spin-only value of 3.87μB/f.u. for high-spin Co2+ indicate a significant orbital contribution in the compounds under study.

Synthesis, Characterization, and X-Ray Crystal Structure of Bis(O-amyl dithiocarbonato-κ2S,S′)bis(4-cyanopyridine-κN)nickel(II)

The [Ni(S2CO-n-C5H11)2(C6H4N2)2] adduct of 4-cyanopyridine with [Ni(S2CO-n-C5H11)2] was synthesized and characterized by elemental analysis, magnetic susceptibility measurement, IR, electronic spectral data, and X-ray diffraction analysis. The Ni atom in the title complex is octahedrally coordinated within a trans-N2S4 donor set, with the Ni atom located on a centre of inversion. The title compound exhibits magnetic moment value (3.20 B.M) which is in agreement with magnetic moment values observed for paramagnetic octahedral complexes of nickel(II). The title complex crystallizes in the orthorhombic space group Pbca with unit cell parameters a = 11.455(5), b = 9.602(4), and c = 26.374(1) Å. Crystal structure was solved by direct methods and refined by full matrix least-squares procedures to a final R value of 0.0499 for 2004 observed reflections. The amyl chain is disordered over two sets of sites, with occupancy ratios of 0.595 : 0.405. Infinite long chains of molecules are formed with the help of C–H⋯N hydrogen bond.

Characterization of iron ferromagnetism by the local atomic volume: from three-dimensional structures to isolated atoms

We present a comprehensive study of the relationship between the ferromagnetism and the structural properties of Fe systems from three-dimensional ones to isolated atoms based on the spin-density functional theory. We have found a relation between the magnetic moment and the volume of the Voronoi polyhedron, determining, in most cases, the value of the total magnetic moment as a function of this volume with an average accuracy of ±0.28 μB and of the 3d magnetic moment with an average accuracy of ±0.07 μB when the atomic volume is larger than 22 Å3. It is demonstrated that this approach is applicable for many three-dimensional systems, including high-symmetry structures of perfect body-centered cubic (bcc), face-centered cubic (fcc), hexagonal close-packed (hcp), double hexagonal close-packed (dhcp), and simple cubic (sc) crystals, as well as for lower-symmetry ones, for example atoms near a grain boundary (GB) or a surface, around a vacancy or in a linear chain (for low-dimensional cases, we provide a generalized definition of the Voronoi polyhedron). Also, we extend the validity of the Stoner model to low-dimensional structures, such as atomic chains, free-standing monolayers and surfaces, determining the Stoner parameter for these systems. The ratio of the 3d-exchange splitting to the magnetic moment, corresponding to the Stoner parameter, is found to be I3d = (0.998 ± 0.006) eV /μB for magnetic moments up to 3.0 μB. Further, the 3d exchange splitting changes nearly linearly in the region of higher magnetic moments (3.0–4.0 μB) and the corresponding Stoner exchange parameter equals . The existence of these two regions reflects the fact that, with increasing Voronoi volume, the 3d bands separate first and, consequently, the 3d magnetic moment increases. When the Voronoi volume is sufficiently large (≥22 Å3), the separation of the 3d bands is complete and the magnetic moment reaches a value of 3.0 μB. Then, when the volume further increases, the 4s bands start to separate, increasing thus the 4s magnetic moment. Surprisingly, in the region of higher magnetic moments (≥3.0 μB), there is also a linear relationship between the 4s exchange splitting and the total magnetic moment with a slope of eV /μB, which is nearly identical to I3d for magnetic moments up to 3.0 μB. These linear relations can be considered as an extension of the Stoner model for low-dimensional systems.

Towards a high-precision measurement of the antiproton magnetic moment

The recent observation of single spins flips with a single proton in a Penning trap opens the way to measure the proton magnetic moment with high precision. Based on this success, which has been achieved with our apparatus at the University of Mainz, we demonstrated recently the first application of the so called double Penning-trap method with a single proton. This is a major step towards a measurement of the proton magnetic moment with ppb precision. To apply this method to a single trapped antiproton our collaboration is currently setting up a companion experiment at the antiproton decelerator of CERN. This effort is recognized as the Baryon Antibaryon Symmetry Experiment (BASE). A comparison of both magnetic moment values will provide a stringent test of CPT invariance with baryons.

A novel sulfur–nitrogen π-heterocyclic radical anion, (6H-1,2,3-benzodithiazol-6-ylidene)malononitrilidyl, and its homo- and heterospin salts

(6H-1,2,3-Benzodithiazol-6-ylidene)malononitrile (4) was electrochemically and chemically reduced with tetrakis(dimethylamino)ethylene (TDAE) and CrTol2 into the title radical anion (5). The electrochemically generated 5 and its salts [TDAE]2+[5]2 (7) and [CrTol2]+ [5] (8) were characterized by solution EPR in combination with UV–Vis spectroscopy. Salts 7 and 8 were isolated and characterized by elemental analysis and solid-state EPR, and 8 by magnetic measurements in the temperature range 2–300K. The value of the effective magnetic moment of the salt 8 at 300K, μeff=1.64μB, indicates π-dimerization of 5 in the solid state. For the molar magnetic susceptibility χ of 8, the temperature dependences of χT and 1/χ in the range 2–300K can be approximated by the Curie–Weiss law with the Curie–Weiss constant C and temperature Tc equal to 0.33±0.01cm3Kmol−1 and −1.0±0.1K, respectively. In the mean-field approximation, the effective value of the exchange interaction of [CrTol2]+ with its neighboring cations can be estimated as zJ=−1.4сm−1. All the experimental results were supported by DFT calculations.

Structural, electronic and magnetic properties of Fe, Co, Ni monatomic nanochains encapsulated in BeO nanotubes bundle

First-principles calculations have been performed to determine the structural, electronic and magnetic properties of transition metal TM (TM = Fe, Co and Ni) monatomic nanochain encapsulated inside and between (9, 0) beryllium oxide nanotube (BeONT) bundle. The generalized gradient approximation (GGA) was employed to describe the exchange-correlation potential. Our results show that the geometrical structure of the BeONT bundle is significantly changed after encapsulating TM nanochains. All configurations of TM chains @ (9, 0) BeONTs bundle systems have negative formation energy so they are stable and exothermic. Total density of states and partial densities of states analyses show that the spin polarization and the magnetic moment of TM chains @ BeONT systems come mostly from the TM atoms chain. The values of total and partial magnetic moment, spin polarization and Stoner parameter are calculated for all configurations of TM chains @ (9, 0) BeONTs bundle systems.

Limits on the neutrino magnetic dipole moment from the luminosity function of hot white dwarfs

Recent determinations of the white dwarf luminosity function (WDLF) from very large surveys have extended our knowledge of the WDLF to very high luminosities. This, together with the availability of new full evolutionary white dwarf models that are reliable at high luminosities, have opened the possibility of testing particle emission in the core of very hot white dwarfs, where neutrino processes are dominant. We use the available WDLFs from the Sloan Digital Sky Survey and the SuperCOSMOS Sky Survey to constrain the value of the neutrino magnetic dipole moment ($\mu_\nu$). We constructed theoretical WDLFs for different values of $\mu_\nu$ and performed a $\chi^2$-test to derive constraints on the value of $\mu_\nu$. We also constructed a unified WDLF by averaging the SDSS and SSS and estimated the uncertainties by taking into account the differences between the WDLF at each magnitude bin. Then we compared all WDLFs with theoretical WDLFs.Comparison between theoretical WDLFs and both the SDSS and the averaged WDLF indicates that $\mu_\nu$ should be $\mu_\nu<5\times 10^{-12}\, e\hbar/(2m_e c)$. In particular, a $\chi^2$-test on the averaged WDLF suggests that observations of the disk WDLF exclude values of $\mu_\nu>5\times 10^{-12}e\hbar/(2m_e c)$ at more than a 95\% confidence level, even when conservative estimates of the uncertainties are adopted. Our study shows that modern WDLFs, which extend to the high-luminosity regime, are an excellent tool for constraining the emission of particles in the core of hot white dwarfs. However, discrepancies between different WDLFs suggest there might be some relevant unaccounted systematic errors. A larger set of completely independent WDLFs, as well as more detailed studies of the theoretical WDLFs and their own uncertainties, is desirable to explore the systematic uncertainties behind this constraint.

Carbohydrate-Appended Tumor Targeting Iron(III) Complexes Showing Photocytotoxicity in Red Light

Glucose-appended photocytotoxic iron(III) complexes of a tridentate Schiff base phenolate ligand [Fe(bpyag)(L)](NO3) (1-3), where bpyag is N,N-bis(2-pyridylmethyl)-2-aminoethyl-β-D-glucopyranoside and H2L is 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one (H2phap) in 1, 3-(2-hydroxyphenylimino)-9-anthrylbutan-1-one (H2anap) in 2, and 3-(2-hydroxyphenylimino)-1-pyrenylbutan-1-one (H2pyap) in 3, were synthesized and characterized. The complex [Fe(dpma)(anap)](NO3) (4), having bis-(2-pyridylmethyl)benzylamine (dpma), in which the glucose moiety of bpyag is substituted by a phenyl group, was used as a control, and the complex [Fe(dpma)(anap)](PF6) (4a) was structurally characterized by X-ray crystallography. The structure shows a FeN4O2 core in a distorted octahedral geometry. The high-spin iron(III) complexes with magnetic moment value of ∼5.9 μB showed a low-energy phenolate-to-Fe(III) charge-transfer (CT) absorption band as a shoulder near 500 nm with a tail extending to 700 nm and an irreversible Fe(III)-Fe(II) redox couple near -0.6 V versus saturated calomel electrode. The complexes are avid binders to calf thymus DNA and showed photocleavage of supercoiled pUC19 DNA in red (647 nm) and green (532 nm) light. Complexes 2 and 3 displayed significant photocytotoxicity in red light, with an IC50 value of ∼20 μM in HeLa and HaCaT cells, and no significant toxicity in dark. The cell death is via an apoptotic pathway, by generation of reactive oxygen species. Preferential internalization of the carbohydrate-appended complexes 2 and 3 was evidenced in HeLa cells as compared to the control complex 4. A 5-fold increase in the cellular uptake was observed for the active complexes in HeLa cells. The photophysical properties of the complexes are rationalized from the density functional theory calculations.

Magnetic and dielectric interactions in nano zinc ferrite powder: Prepared by self-sustainable propellant chemistry technique

The structural, magnetic and dielectric properties of nano zinc ferrite prepared by the propellant chemistry technique are studied. The PXRD measurement at room temperature reveal that the compound is in cubic spinel phase, belong to the space group Fd−3m. The unit cell parameters have been estimated from Rietveld refinement. The calculated force constants from FTIR spectrum corresponding to octahedral and tetrahedral sites at 375 and 542cm−1 are 6.61×102 and 3.77×102Nm−1 respectively; these values are slightly higher compared to the other ferrite systems. Magnetic hysteresis and EPR spectra show superparamagnetic property nearly to room temperature due to comparison values between magnetic anisotropy energy and the thermal energy. The calculated values of saturation magnetization, remenant magnetization, coercive field and magnetic moment supports for the existence of multi domain particles in the sample. The temperature dependent magnetic field shows the spin freezing state at 30K and the blocking temperature at above room temperature. The frequency dependent dielectric interactions show the variation of dielectric constant, dielectric loss and impedance as similar to other ferrite systems. The AC conductivity in the prepared sample is due to the presence of electrons, holes and polarons. The synthesized material is suitable for nano-electronics and biomedical applications.

Preparation and characterization of iron(iii) complex of saccharin

Complex of iron(III) with saccharin, [Fe(C7H4O3SN)2Cl] has been prepared in aqueous medium. The IR and electronic spectral analysis suggest that two saccharin molecules are attached to the metal ion through N atom and there is no chemically coordinated or crystalline water in the complex molecule. The magnetic moment value indicates the paramagnetic character of the complex. The cyclic voltammetric study indicates a quasi-reversible electron transfer process due to the presence of iron in the compound. DOI: http://dx.doi.org/10.3329/jbas.v37i2.17560 Journal of Bangladesh Academy of Sciences, Vol. 37, No. 2, 195-203, 2013

15]aneN4S: Synthesis, Thermodynamic Studies and Potential Applications in Chelation Therapy

The purpose of this work was to synthesize and characterize the thiatetraaza macrocycle 1-thia-4,7,10,13-tetraazacyclopentadecane ([15]aneN4S). Its acid-base behaviour was studied by potentiometry at 25 °C and ionic strength 0.10 M in KNO3. The protonation sequence of this ligand was investigated by 1H-NMR titration that also allowed the determination of protonation constants in D2O. Binding studies of [15]aneN4S with Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ metal ions were further performed under the same experimental conditions. The results demonstrated that this compound has a higher selectivity and thermodynamic stability for Hg2+ and Cu2+, followed by Ni2+. The UV-visible-near IR spectroscopies and magnetic moment data for the Co(II) and Ni(II) complexes indicated a tetragonal distorted coordination geometry for both metal centres. The value of magnetic moment and the X-band EPR spectra of the Cu(II) complex are consistent with a distorted square pyramidal geometry.

Comparative Study of Magnetic Properties of Nanoparticles by High-Frequency Heat Dissipation and Conventional Magnetometry

The rate of heating of 15 nm uniformly-sized magnetic aqueous nanoparticles suspension by high-amplitude and high-frequency ac magnetic field induced by the resonating LC circuit was measured. The results are analyzed in terms of specific energy absorption rate (SAR). Fitting field amplitude and frequency dependences of SAR to the linear response theory, magnetic moment per particles was extracted. The value of magnetic moment was independently evaluated from dc magnetization measurements of a frozen colloid by fitting field-dependent magnetization to a Langevin function. The two methods produced similar results, which are compared to the theoretical expectation for this particle size. Additionally, analysis of SAR curves yielded effective relaxation time.

Electronic structure and spectra of CuO

We report the electronic structure of monoclinic CuO as obtained from first principles calculations utilizing density functional theory plus effective Coulomb interaction (DFT + U) method. In contrast to standard DFT calculations taking into account electronic correlations in DFT + U gave antiferromagnetic insulator with energy gap and magnetic moment values in good agreement with experimental data. The electronic states around the Fermi level are formed by partially filled Cu 3$d_{x^2-y^2}$ orbitals with significant admixture of O 2$p$ states. Theoretical spectra are calculated using DFT + U electronic structure method and their comparison with experimental photoemission and optical spectra show very good agreement.

Hadron production ine+e−collisions atBABARand implications on the muon anomalous magnetic moment

The BABAR Collaboration has an intensive program of studying hadronic cross sections at low-energy e+e− collisions, accessible via initial-state radiation. Our measurements allow significant improvements in the precision of the predicted value of the muon anomalous magnetic moment. These improvements are necessary for shedding light on the current ∼ 3.5σ difference between the predicted and the experimental values. We have published results on a number of processes with two to six hadrons in the final state. We report here the results of recent studies with the final states which constitute the main contribution to the hadronic cross section in the energy region between 1 and 3 GeV, as e+e− → K+K−, e+e− → KS0KL0 and e+e− → 4 hadrons.

Magnetic Properties of Zn1-xCoxO Nanoparticles.

Zn1-xCoxO nanoparticles have been synthesized at various concentrations of Co2+ doping (0.005 ≤ x ≥ 0.15) by wet chemical method. Particle size was ranging from 34 – 45nm. The magnetic moment increases from x = 0.005 and 0.01 sample to x = 0.04 sample drastically showing a value of magnetic moment as high as 8.54μB/Cations and then decreases for x = 0.09 and 0.15 values of Co2+ doping. There is almost paramagnetic behaviour for x = 0.005 and 0.01 Co2+ doped samples. The x = 0.04 sample shows ferromagnetic ordering. Ferromagnetic behaviour decreases for x = 0.09 and 0.15 samples as the antiferromagnetic interaction dominates at higher Co2+ doping concentrations. To probe the source of magnetism, we have undertaken photolu-minescence studies also which revealed the presence of oxygen and Zinc vacancies along with other defects.

Magnetic moments of odd-odd spherical nuclei

Magnetic moments of more than one hundred odd-odd spherical nuclei in ground and excited states are calculated within the self-consistent TFFS based on the EDF method by Fayans et al. We limit ourselves to nuclei with a neutron and a proton particle (hole) added to the magic or semimagic core. A simple model of no interaction between the odd nucleons is used. In most of the cases we analyzed, a good agreement with the experimental data is obtained. Several cases are considered where this simple model does not work and it is necessary to go beyond. The unknown values of magnetic moments of many unstable odd and odd-odd nuclei are predicted including sixty values for excited odd-odd nuclei.

Synthesis and Characterization of mixed ligand complexes of Co(II) ion with some N and S donor

Mixed ligand complexes of Co(II) ion with some heterocyclic nitrogen donors and 1,1-dicyanoethylene-2,2-dithiolate of the compositions, Co(N-N)2(i-MNT), Co(N-N)(i-MNT).2H2O and Co(N-N)(i-MNT)L2 (N-N = 1,10-phenanthroline, 2,2'-bipyridine ; i-MNT 2- = 1,1-dicyano- ethylene -2,2- dithiolate ; L = pyridine(py), -picoline (-pic), -picoline (-pic) or -picoline (-pic) have been isolated and characterized on the basis of analytical data, molar conductance, magnetic susceptibility, electronic and infrared spectral studies. The molar conductance data reveal non-electrolytic nature of the complexes in DMF. Magnetic moment values suggest low spin complexes. The electronic spectral data suggest distorted octahedral stereochemistry around Co(II) ion in these complexes. Infrared spectral studies suggest bidentate chelating behaviour of i-MNT 2- , 1,10-phenanthroline and 2,2'-bipyridine while other ligands show unidentate