CALCULATION OF THE RESONANT MAGNETO-OPTICAL PROPERTIES OF TRANSITION METALS AND DISORDERED ALLOYS IN THE X-RAY REGIME

2002 ◽  
Vol 09 (02) ◽  
pp. 1179-1183
Author(s):  
J. MINÁR ◽  
H. EBERT
Keyword(s):  
Optical Properties ◽  
Green’S Function ◽  
Green's Function ◽  
Local Magnetic Moment ◽  
X Ray ◽  
Disordered Alloys ◽  
Spin Polarized ◽  
Experimental Findings ◽  
Good Agreement ◽  
Disordered Alloy

A version of the Kubo formula is presented, which allows one to calculate the resonant magneto-optical properties in the X-ray regime for arbitrary materials. This is achieved by representing the underlying electronic structure in terms of the electronic Green's function. Calculating the Green's function within the framework of spin-polarized relativistic multiple scattering theory (SPR-KKR) in particular gives access to spin–orbit-induced resonant magneto-optical properties. Results obtained for the Faraday effect and for the magnetic dichroic part of the complex reflective index n at the K-edge of Co and L 2,3-edges of Fe are found in very good agreement with recent experimental findings. The relation of n with the local magnetic moment is discussed on the basis of the calculated results for the L 3-edges of Pt in fcc-Co x Pt 1-x disordered alloy.

Non-Equilibrium Green’s Function Modeling of the Transport Characteristics of Magnetic Tunnel Junctions Containing Anderson Impurities

SPIN ◽  
2020 ◽  
Vol 10 (01) ◽  
pp. 2050006
Author(s):  
Parvathy Harikumar ◽  
S. Mathi Jaya
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Tunnel Junctions ◽  
Magnetic Tunnel Junctions ◽  
Many Body ◽  
Applied Bias ◽  
Tunnel Current ◽  
Spin Polarized ◽  
Barrier Region ◽  
Non Equilibrium Green’S Function

A nonequilibrium Green’s function (NEGF) formulation to study the transport characteristics of magnetic tunnel junctions (MTJs) that contains impurities at the barrier region and many-body interaction at the electrode region is presented. The formulation makes use of the already developed NEGF method for MTJs without any impurities and the impurity Green’s function is obtained using Haldane’s approach that explicitly takes into account the on-site Coulomb interaction ([Formula: see text]) of the impurity. The formulation is used to obtain the spin-dependent tunnel current of model MTJs as a function of the applied bias for different values of [Formula: see text] corresponding to both the parallel and antiparallel configuration of the end electrodes of the MTJ. The tunnel currents are used to obtain the tunnel magnetoresistance (TMR) of the MTJ and we observed from our study that the TMR is strongly influenced by the impurities. The TMR is found to be reduced compared to that of the MTJ without impurities and the bias dependence of the TMR is found to be strongly influenced by [Formula: see text]. Our studies revealed that the MTJ can exhibit almost completely spin polarized current at certain values of [Formula: see text].

Nickel Corrosion Inhibition in Sulfuric Acid—Electrochemical Studies, Morphologies, and Theoretical Approach

CORROSION ◽  
10.5006/0508 ◽  
2012 ◽  
Vol 68 (8) ◽  
pp. 699-712 ◽  
Author(s):  
M.A. Amin ◽  
H. Shokry ◽  
E.M. Mabrouk
Keyword(s):  
Sulfuric Acid ◽  
Electrochemical Impedance ◽  
Theoretical Studies ◽  
Electrochemical Studies ◽  
X Ray ◽  
Linear Polarization Resistance ◽  
Tafel Polarization ◽  
Inhibition Performance ◽  
Experimental Findings ◽  
Good Agreement

The inhibition performance of three selected dihydrazide derivatives, namely, malonic acid (MAD), succinic acid (SAD), and adipic acid (AAD) dihydrazide, was tested in relation to nickel corrosion in 1.0 M sulfuric acid (H2SO4) solution. Electrochemical methods (Tafel polarization, linear polarization resistance [LPR], and electrochemical impedance spectroscopy [EIS]) were used, complemented with scanning electron microscopy/energy-dispersive x-ray (SEM/EDX) examinations. Computational studies were also used to confirm experimental findings and to optimize the adsorption structures of dihydrazide derivatives. Results showed that the three tested dihydrazides inhibited Ni corrosion (mixed-type inhibitors) to an extent, depending on the type and concentration of the introduced inhibitor. SEM studies revealed that the corroded areas on the surface were decreased in the presence of additives to an extent, depending on the type and concentration of the tested inhibitor. Results obtained from electrochemical measurements are in good agreement with theoretical studies.

scholarly journals Structure and Optical Properties of B'- Phase of Ag8SnSe6

2016 ◽  
Vol 17 (3) ◽  
pp. 346-349
Author(s):  
І.V. Semkiv
Keyword(s):  
Crystal Structure ◽  
Optical Properties ◽  
Absorption Spectrum ◽  
Optical Absorption ◽  
Experimental Studies ◽  
Energy Dispersive Spectrum ◽  
Energy Dispersive ◽  
Interatomic Distances ◽  
X Ray ◽  
Good Agreement

Energy dispersive x-ray spectroscopy of lowtemperature b¢-Ag8SnSe6 crystalcarried out. Energy dispersive spectrum shows only peaks related to Ag8SnSe6. Experimental optical absorption spectrum and band gap value 0.82 eV are determined. Theoretical calculation of absorption spectrum shows good agreement with experimental studies. Modeling of crystal structure of Ag8SnSe6 argyrodite and interatomic distances calculation are carried out.

scholarly journals Equation-of-Motion Coupled-Cluster Cumulant Green’s Function for Excited States and X-Ray Spectra

2021 ◽  
Vol 9 ◽  
Author(s):  
F. D. Vila ◽  
J. J. Kas ◽  
J. J. Rehr ◽  
K. Kowalski ◽  
B. Peng
Keyword(s):  
Green’S Function ◽  
Spectral Function ◽  
Excited States ◽  
Green's Function ◽  
Coupled Cluster ◽  
X Ray ◽  
Molecular Systems ◽  
Self Energy ◽  
The Core ◽  
Non Linear

Green’s function methods provide a robust, general framework within many-body theory for treating electron correlation in both excited states and x-ray spectra. Conventional methods using the Dyson equation or the cumulant expansion are typically based on the GW self-energy approximation. In order to extend this approximation in molecular systems, a non-perturbative real-time coupled-cluster cumulant Green’s function approach has been introduced, where the cumulant is obtained as the solution to a system of coupled first order, non-linear differential equations. This approach naturally includes non-linear corrections to conventional cumulant Green’s function techniques where the cumulant is linear in the GW self-energy. The method yields the spectral function for the core Green’s function, which is directly related to the x-ray photoemission spectra (XPS) of molecular systems. The approach also yields very good results for binding energies and satellite excitations. The x-ray absorption spectrum (XAS) is then calculated using a convolution of the core spectral function and an effective, one-body XAS. Here this approach is extended to include the full coupled-cluster-singles (CCS) core Green’s function by including the complete form of the non-linear contributions to the cumulant as well as all single, double, and triple cluster excitations in the CC amplitude equations. This approach naturally builds in orthogonality and shake-up effects analogous to those in the Mahan-Noizeres-de Dominicis edge singularity corrections that enhance the XAS near the edge. The method is illustrated for the XPS and XAS of NH3.

Electronic Structure and Magnetic State of TiSe2 Doped with Cr by Means of Intercalation or Substitution of Ti

2010 ◽  
Vol 168-169 ◽  
pp. 380-383 ◽  
Author(s):  
A.S. Shkvarin ◽  
A.I. Merentsov ◽  
Y.M. Yarmoshenko ◽  
N.A. Skorikov ◽  
A.N. Titov
Keyword(s):  
Magnetic State ◽  
Local Density ◽  
Local Magnetic Moment ◽  
Host Lattice ◽  
Local Density Of States ◽  
Half Metallic ◽  
Spin Polarized ◽  
Band Spectra ◽  
Grown Structure ◽  
Good Agreement

Solid solutions 1T-CrxTi1-xSe2 (x = 0-0,83) were synthesized. Single crystals in the concentration range x = 0-0.69 were grown. Structure of these materials was studied on single- and polycrystalline samples. It was determined that chromium atoms substitute for titanium atoms in the TiSe2 host lattice. XPS measurements of the core levels together with the resonance valence band spectra of the 1T-CrxTi1-xSe2, as well as absorption spectra of Ti and Cr were performed. According to the experimental XAS data and multiplet atomic calculation, titanium and chromium atoms have oxidation numbers of +4 and +3, respectively. The local magnetic moment of about 3 eV is detected at Cr atoms. A transition into the spin glass state is observed. The modeling calculations of chromium local density of states were carried out. These results are in a good agreement with the experimental ones and suggest that 3d density of electronic states of chromium that substitutes for titanium in the host lattice is spin polarized and has a half-metallic character.

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