Transition Metals Iron Research Articles

Temperature dependent dynamic susceptibility calculations for itinerant ferromagnets

Inelastic neutron scattering experiments have revealed a variety of interesting and unusual phenomena associated with the spin dynamics of the 3-d transition metal ferromagnets nickel and iron. An extensive series of calculations based on the itinerant electron formalism has demonstrated that the itinerant model does provide an excellent quantitative as well as qualitative description of the measured spin dynamics of both nickel and iron at low temperatures. Recent angular resolved photoemission experiments have indicated that there is a rather strong temperature dependence of the electronic spin-splitting which, from relatively crude arguments, appears to be inconsistent with neutron scattering results. In order to investigate this point and also the origin of spin-wave renormalization, a series of calculations of the dynamic susceptibility of nickel and iron has been undertaken. The results of these calculations indicate that a discrepancy exists between the interpretations of neutron and photoemission experimental results regarding the temperature dependence of the spin-splitting of the electronic energy bands.

NMR study of the3dferromagnetic metals: Critical region and paramagnetic phase

The ferromagnetic transition metals iron, nickel, and cobalt have been investigated by nuclear magnetic resonance up to the critical region and, in the case of nickel and cobalt, in the paramagnetic phase. The measurements include the zero-field resonant frequency, spin-spin relaxation rate, and spin-lattice relaxation rate in the ferromagnetic phase, and the Knight shift and spin-lattice relaxation rate in the paramagnetic phase. The data yield values of the static critical exponent ($\ensuremath{\beta}$) for the spontaneous magnetization and the dynamic exponent ($z$) for spin fluctuations near the critical points of all three ferromagnetic metals. Paramagnetic-phase data for nickel and cobalt yield the $d$-spin hyperfine coupling and the orbital Knight shift and susceptibility contributions. Magnetic equation-of-state parameters are derived for nickel and cobalt. Noncritical spin-spin relaxation rates in the ferromagnetic phase are attributed mainly to Suhl-Nakamura interactions, but in bulk metal samples the rates exhibit a striking and unexplained maximum between room temperature and the critical point.

Matrix isolation studies of bimetallic molecules of Fe–M(3d) metals

A systematic study of the iron–M(3d) molecules (M = Mn, Fe, Co, Ni, Cu) was carried out using matrix isolation techniques in conjunction with Mössbauer spectroscopy. From the Mössbauer parameter of the isolated species it was possible to determine their electronic ground state. The bonding between the various transition metal atoms and iron varies appreciably. The strongest bond is associated with the molecules having an odd number of electrons. The isomer shift of FeNi is very close to that obtained for iron monomers in rare gas solids (weakest bond molecule). In contrast, FeCo has a more positive isomer shift, closer to that expected for 3d74s configuration at the iron atom.

Band theoretic interpretation of neutron scattering experiments in metallic ferromagnets

Magnetic excitations in the 3d transition metal ferromagnets nickel and iron have been found to possess unusual properties not found in other magnetic systems. For example, inelastic neutron scattering experiments have revealed that spinwaves do not exist at wave-vectors above a particular cut-off value while below this cut-off point they have been observed well above the Curie temperature. This behaviour is not consistent with predictions of localized spin models but can be explained by the band theoretic, or itinerant electron theory. In fact, first principles calculations of the low temperature neutron scattering cross-section based on the itinerant model have been shown to be in excellent agreement with experiment. In addition, the prediction of an optical spin-wave mode has been recently confirmed. The finite temperature extrapolation of the low temperature theory based on the traditional concept of a temperature-dependent spin-splitting of the electronic energy bands appears to be inconsistent with experiment. A more realistic first principles approach to develop a correct finite temperature theory is under investigation.

Hyperfine fields and neutron scattering in ferromagnetic metals

The origin of ferromagnetism in the transition metal ferromagnets, iron, cobalt, and nickel is discussed, from an ab initio band structure point of view, with proper attention to the explicit roles of exchange, correlation and hybridization effects. The influence of these effects and all the mechanisms such as direct, exchange core polarization and many-body effects that have been found important for the hyperfine properties of atomic systems are included in attempting to understand the experimentally observed hyperfine fields at the nuclei in these metals. Spin-density distributions using calculated spin polarized band wave-functions are used to make comparisons with experimental neutron scattering data. The impact of the results of analyses of hyperfine fields at the nuclei and spin density distributions on the origin of hyperfine fields at muon sites is discussed. This talk, and the corresponding article for the proceedings of this conference, will deal with the theoretical understanding of the hyperfine fields at the nuclei and neutron scattering form factors in the three ferromagnetic metals, iron, cobalt and nickel and the impact of this understanding on that of the origin of the hyperfine fields at positive muon sites in these metals. With these aims in mind, the plan of my talk will be the following.

On the Origin of Asymmetry of XES and XPS Core Lines of Iron Transition Metals: Experiment on Cu–Mn Alloys

The author shows that the width and asymmetry of the Mn Kα1 (1s1/2-2p3/2) X-ray emission line correlate with a magneton number of Mn atoms in copper-manganese binary alloys. This correlation seems to originate from exchange interaction between a core hole (2p) and unpaired 3d electrons in Mn. The author suggests that 2p-3d interaction is probably a more significant effect than many-body final state effects in shaping the Kα X-ray emission and 2p photoemission lines for pure iron transition metals and their alloys.

Influence of many-body effects and intra-atomic exchange interactions on the shape of x-ray emission and photoemission lines of3dmetals

The asymmetry and width of the x-ray emission and x-ray photoemission lines of iron transition metals are discussed in terms of many-body final-state effects and of the exchange interaction between a core hole and unpaired $3d$ electrons.

Ferromagnetic properties of some new metallic glasses

Continuously cast metallic glasses [METGLASR (trademark of the Allied Chemical Corporation) alloys] based on the transition metals (TM) iron, cobalt, and nickel can now be synthesized containing boron as the only metalloid. The different electron-donor effects of boron and phosphorus are clearly seen for the first time; each atom of these metalloids gives ∼1.6 and 2.4 electrons, respectively, to the TM d bands. Extrapolation of the available magnetic moment data suggests a nonzero moment on nickel in (TM)80B20 glasses. The boron-containing metallic glasses generally show higher Curie temperatures and room-temperature saturation magnetizations than mixed-metalloid glassy alloys of the same TM content.

Further cluster calculations of the electronic spectra of transition metals

An expression derived by Lloyd (1967) for the density of states of a system of nonoverlapping scattering centres is used to evaluate the electronic spectra of the transition metals iron, nickel and copper. The results of these calculations are compared with previous work and analysed to ascertain the range of applicability of this approach. It is found that the cluster method provides a practical approach to the study of the electronic spectra of strongly interacting systems, such as the solid and liquid transition metals considered here, when they are characterized by a sharp single site resonance closely approaching the ideal Breit-Wigner form.

Metal-ion concentrations in sea-surface microlayer and size-separated atmospheric aerosol samples in Hawaii

A number of sea-surface microlayer and marine atmosphere samples have been taken from sites in Hawaii over a 2-year period from June 1969 to June 1971. The analysis of samples is reported for sodium, potassium, calcium, magnesium, strontium, copper, iron, and zinc, and some analyses of microlayer samples for marine nutrients are reported as total carbon, total phosphorus, and reactive nitrate. Data collected show chemical compositions and ion ratios of most samples to differ, often drastically, from normal sea-water data also collected for these chemical species. Microlayer samples represent a thin film approximately 150 μ thick removed from the surface of the open ocean. These samples generally have considerably higher total carbon, phosphorus, and nitrate concentrations than samples taken at the same site but at 0.6-meter depth. Microlayer samples are also found to be enriched to a small extent in some alkaline earth metals and to a much larger extent for the transition metals copper, iron, and zinc. The transition metals were also found to be proportionately more organically associated in the microlayer samples. Aerosol samples studied are enriched in most metals relative to sodium and to the metal to sodium ratio found in sea water. These enrichments range from values very close to zero up to unity or so for the alkali and alkaline earth metals, depending on element and particle size. Average enrichment values for the transition metals on smaller aerosols approach and exceed 3 and 4 orders of magnitude. Generally, enrichments are greatest on the smaller aerosols approaching Aitkin size; values are also pronounced for the giant aerosols, and lesser values occur for the intermediate-sized large aerosols. It is possible to consider the data in terms of mixing of globally spread, stratospheric continental dust of long residence time and pollution aerosols with normal marine aerosols. It is also important to consider separately or in combination with this concept fractionation and enrichment of selected chemical species before their ejection from the sea surface during agitation and bubbling. A qualitative mass spectrographic study of some of the samples indicates that organic coating materials on the aerosols are more concentrated on the smaller aerosols.

Resonanz-Raman-Effekt von Thiocyanatkomplexen einiger Übergangsmetalle

Abstract The thiocyanates of the transition metals iron, cobalt, copper as well as of rhenium and of tech-netium appear in solution as strongly coloured complexes. The resonance raman bands in the sol-vent acetonitrile are investigated. To achieve an unambiguous identification the infrared spectra were recorded too. The change in position and structure of the acetonitrile bands indicates strong complexation of iron, cobalt and copper with acetonitrile, thus indicating the existence of mixed acetonitrile-thiocyanate complexes. The resonance raman spectra of the rhenium-and technetium-thiocyanates present as tetramethyl ammonium salts show however no raman-and infrared-bands of complexed acetonitrile molecules. In the raman spectrum of the thiocyanates of iron, cobalt and copper mainly the totally sym-metric C≡N, S-C, Me-S and Me-N valence vibrations are observed, among which the S-C vibration shows a remarkably high intensity. Besides, a series of bands is obtained which is inter-preted partly as caused by decay products, and partly as bands of complexed acetonitrile. The thiocyanates of rhenium and of technetium show the three possible valence vibrations only. The high frequency of the S-C valence indicates the N-coordination of the thiocyanate group.

Analysis of Metal in Wastewater Collected from Three Pharmaceutical Industries Located in Tongi Area of Gazipur District

Wastewater qualities of three pharmaceutical industries were determined during July 2005 to January 2006. Alkaline earth metals including calcium (Ca) and magnesium (Mg) of wastewater ranged 41.79-54.5mgL-1 and 10.5996-32.2926 mgL-1, respectively. Alkali metals including potassium (K) and sodium (Na) of wastewater ranged 3.44-18.98 mgL-1 and 67.57- 128.71 mgL-1, respectively. Transition metal iron (Fe) ranged 1.02-2.13 mgL-1. On an average metals including zinc (Zn), lead (Pb), nickel (Ni) and cadmium (Cd) were in trace amount i.e. 84.32 μ gL-1, 11.59 μ gL-1, 4.96 μ gL-1 and 0.1047 μ gL-1, respectively in the wastewater. Copper (Cu) was undetected in wastewater. The average amount of iron of site N, magnesium of site S and potassium of site B of wastewater were higher than that of the standard of Department of Environment (DoE) of Bangladesh. Key words: Metals; Pharmaceutical wastewater; DoE standards. DOI: 10.3329/bjsir.v45i3.6538Bangladesh J. Sci. Ind. Res. 45(3), 277-282, 2010

Photoemission Studies of the Electronic Structure of Transition Metals

New photoemission studies of the optical densities of states of several transition metals (nickel, cobalt, iron, manganese, and chromium) and copper are reported. Experimental results are compared with theoretical one-electron energy-band densities of states. The principal results of these studies are: (1) New structure is observed which shows encouraging agreement with magnetic one-electron energy-band calculations, and (2) the large anomalous peaks in ferromagnetic Ni, Co, and Fe about 5 eV below the Fermi level which were previously reported by others have been found to be due to spurious surface effects. The two largest peaks observed in the optical densities of states of ferromagnetic Ni and Fe and anti-ferromagnetic Cr agree within 0.15 eV, respectively, with the two largest peaks in calculated magnetic energy-band densities of states for each of these metals.

Infra-red spectra of metal complex ions below 600 cm −1—I : The spectra of the tris complexes of 1, 10-phenanthroline and 2,2′-bipyridine with the transition metals iron(II) through zinc(II)

The infra-red spectra of the tris-2, 2′-bipyridine and the tris-1,10-phenanthroline complexes of iron(II), cobalt(II), nickel(II), copper(II), and zinc(II) have been obtained from 250 to 2000 cm −1. These spectra have been correlated with the bonding properties, and a metal-nitrogen bond vibration assignment has been proposed.

Die Extraktion von Citrat- und Tartrat-Komplexen der �bergangsmetalle

The citrate and tartrate complexes of the transition metals palladium, vanadium, uranium, iron, bismuth, gold, and cerium can be separated as substituted ammonium salts by liquid-liquid extraction from aqueous solutions with organic solvents. The citrate complex of rhodium and the tartrate complex of zirconium can be extracted in a similar manner. The organic solvent and the solution acidity for the best results are tabulated for each element. (J.S.R.)

Paramagnetic Resonance in Trivalent Transition Metal Complexes

Paramagnetic-resonance absorption has been observed in complexes of acetylacetone with the trivalent transition metals titanium, chromium, iron, molybdenum, and ruthenium. The symmetry of the field perturbing the metal ion is predominantly axial. For the complexes of Ti+3 and of Ru+3, the axial potential is negative. Energy-level splittings by the ligand field and g factors were obtained for the various complexes. Resonance was also observed in complexes of trifluoroacetylacetone with chromium and iron and in the complex chromium (III) hexafluoroacetylacetonate. Resonance could not be detected in the complexes vanadium (III) acetylacetonate, manganese (III) acetylacetonate and ferric (III) hexafluoroacetylacetonate, although magnetic-susceptibility measurements on the last two compounds indicated that they were paramagnetic.

Metallic Oxides with the Structure of High-speed Steel Carbide

OXIDES isomorphous with the high-speed steel carbide Fe3W3C have been found to exist with the ideal composition Me3Ti3O, where Me is one of the transition metals manganese, iron, cobalt, nickel or copper (but not vanadium, chromium or zinc).

On a new alkali-metal

The aim of this article is to investigate the sensing performance of NO gas molecule on the graphene nanoribbon domain for the determination of structural and electronic properties. Effect of an alkali metal (lithium) and a transition metal (iron) on the armchair oriented graphene nanoribbon (ArGNR) surface for the sensing purpose of NO gas has been performed through the quantum mechanics based Density Functional Theory (DFT) calculations. Various configurations of ArGNR doped with Li and Fe atoms such as one-edge doped, center doped, both-edge doped Li-ArGNR and Fe-ArGNR have been simulated, and a detailed comparative study of lithium and iron doping on different configurations of ArGNRs for the adsorption energy, stability analysis, band gap analysis and density of states analysis has been quantitatively evaluated. By comparing the adsorption energy of NO, it is found that Li doping enhances the strength of NO adsorption on the different variants of ArGNR. Computational results predict that the undoped ArGNR is insensitive to the NO gas adsorption with adsorption energy of about −0.41 eV. Our results determine that substitutional doping of Li doping at one edge doped and both-edge doped position increases the adsorption abilities of ArGNRs in these configurations with adsorption energies of approximately −6.92 eV and −9.64 eV that is 16 and 23 times greater than the pristine ArGNR (Pr-ArGNR). Band nature for both type of doping estimates the changing behavior of ArGNRs from semiconductor to metallic transition after the adsorption of NO molecule. It is concluded that the Li doping at one edge and both edge position of ArGNR makes it an excellent potential sensing material for the sensing purpose of NO gas as compared to the Fe doped configurations.