Electronic Structure Of Mn Research Articles

First-principles calculations to investigate probing the influence of Mn and Mg doping concentration on electronic structures and transport properties of SnTe alloys

In this paper, the defect formation energies, the nature of chemical bonding, and electronic structures of Mn- and Mg-doped SnTe alloys were determined by first-principles calculations. The effects of substitutional atoms on thermoelectric parameters are analyzed by solving the Boltzmann equation. The solution solubility of Mg in SnTe alloy is higher than that of Mn, and the lattice distortion caused by Mn substituting Sn sites is more severe. In addition, the resonant level of Sn1-xMnxTe alloys possesses a flat trend of the valance band maximum, which improves the effective carrier mass and Seebeck coefficient. The Mg-doped alloys exhibit higher carrier mobility and electrical conductivity. The maximum value of the power factor is 5.78 mWm−1K−2 for the Sn0.97Mn0.03Te alloy. Corresponding directionally-solidified samples with the same composition were also prepared. The Sn0.97Mn0.03Te sample also achieves the highest ZT value of 1.28. These results provide theoretical reference for optimizing the thermoelectric performance of SnTe alloys by substituting atoms.

DFT Method Used for Prediction of Molecular and Electronic Structures of Mn(VI) Macrocyclic Complexes with Porhyrazine/Phthalocyanine and Two Oxo Ligands.

By using the data of the DFT quantum chemical calculation in the OPBE/TZVP and B3PW91/TZVP levels, the possibility of the existence of a manganese(VI) heteroligand complex containing porphyrazine or its tetra[benzo] derivative (phthalocyanine) and two oxygen (O2-) ligands, which is still unknown for this element, is shown. The parameters of the molecular structure, multiplicity of the ground state, NBO analysis data and standard thermodynamic parameters (enthalpy ΔH0f, entropy S0f and Gibbs's energy ΔG0f of formation) of each of these metal macrocyclic compounds are presented. Additionally, it is noted that, based on the totality of structural data obtained by the above versions of the DFT method, the existence of a similar complex of manganese with di[benzo] derivative of porhyrazine and two oxygen (O2-) ligands seems doubtful.

Effect of Mn+2 Doping and Vacancy on the Ferromagnetic Cubic 3C-SiC Structure Using First Principles Calculations

Wide bandgap semiconductors doped with transition metals are attracting significant attention in the fabrication of dilute magnetic semiconductor devices (DMSs). The working principle of DMSs is based on the manipulation of the electron spin, which is useful for magnetic memory devices and spintronic applications. Using the density functional theory (DFT) calculation with the GGA+U approximation, we investigated the effect of native defects on the magnetic and electronic structure of Mn+2-doped 3C-SiC structure. Three structures were selected with variations in the distance between two impurities of (Mn+2)-doped 3C-SiC, which are 4.364 Å, 5.345Å, and 6.171 Å, respectively. We found ferromagnetic coupling for single and double Mn+2 dopant atoms in the 3C-SiC structure with magnetic moments of 3 μB and 6 μB respectively. This is due to the double exchange because of p-d orbital hybridization. The p-orbitals of C atoms play important roles in the stability of the ferromagnetic configuration. The impact of Si-vacancy (nearby, far) and C-vacancy (near) of (Mn+2)-doped 3C-SiC plays an important role in the stabilization of AFM due to super-exchange coupling, while the C-vacancy (far) model is stable in FM. All electronic structures of Mn+2-doped 3C-SiC reveal a half-metallic behavior, except for the Si-vacancy and C-vacancy of (nearby), which shows a semiconductor with bandgap of 0.317 and 0.828 eV, respectively. The Curie temperature of (Mn+2)-doped 3C-SiC are all above room temperature. The study shows that native vacancies play a role in tuning the structure from (FM) to (AFM), and this finding is consistent with experiments reported in the literature.

Direct Observation of Interface-Dependent Multidomain State in the BaTiO3 Tunnel Barrier of a Multiferroic Tunnel Junction Memristor.

Multiferroic tunnel junctions (MFTJs), normally consisting of a four-state resistance, have been studied extensively as a potential candidate for nonvolatile memory devices. More interestingly, the MFTJs whose resistance can be tuned continuously with applied voltage were also reported recently. Since the performance of MFTJs is closely related to their interfacial structures, it is necessary to investigate MFTJs at the atomic scale. In this work, atomic-resolution HAADF, ABF, and EELS of the La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 MFTJ memristor have been obtained with aberration-corrected scanning transmission electron microscopy (STEM). These results demonstrate varied degree of interfacial cation intermixing at the bottom BTO/LSMO interface, which has a direct influence on the polarization of the ferroelectric barrier BTO and the electronic structure of Mn near the interfaces. We also took advantage of a simplified model to explain the relation between the interfacial behavior and polarization states, which could be a contributing factor to the transport properties of this MFTJ.

Hydrothermal synthesis of Mn2+ doped titanate nanotubes: Investigation of their structure and room temperature ferromagnetic behavior

Hydrothermal synthesis of Mn2+ doped titanate nanotubes (TNTs), which exhibited room temperature ferromagnetism (RTFM), is reported. Dispersions of 1 and 5 at.% Mn2+ doped anatase TiO2 nanocrystals were used as precursors. Size and shape of Mn2+ doped TNTs and precursor nanocrystals were studied by transmission electron microscopy (TEM). The relatively uniform size distribution of transverse dimension of nanotubes of about 10 nm was observed while their lengths varied up to few hundred nanometers. The X-Ray Diffraction (XRD) analysis and Raman spectroscopy of resultant powder confirmed the hydrogen dititanate (H2Ti2O5 x H2O) crystal phase of Mn2+ doped TNTs with the presence of small amount of sodium titanates. Electron paramagnetic resonance (EPR) experiments were performed to probe the local atomic and electronic structure of Mn in the nanotubes. Room temperature ferromagnetic ordering with saturation magnetic moment (Ms) in the range of 0.6–1.5 μB per Mn atom was observed.

Site preference and electronic structure of Mn2RhZ (Z = Al, Ga, In, Si, Ge, Sn, Sb): a theoretical study

Abstract The electronic structure and magnetism of Mn2RhZ (Z = Al, Ga, In, Si, Ge, Sn, Sb) Heusler alloys have been studied by using first-principles calculations. Three half-metallic ferromagnets, namely, Mn2RhAl, Mn2RhGe and Mn2RhSb have been considered. The calculated equilibrium lattice constant increases with increasing atomic number of Z atoms lying in same column of periodic table. The calculated total magnetic moments Mtot are 2 µB/f.u. for Mn2RhAl and Mn2RhGa, 3 µB/f.u. for Mn2RhSi, Mn2RhGe and Mn2RhSn, and 4 µB/f.u. for Mn2RhSb, which agrees with the Slater-Pauling curve quite well. In all these compounds, except for Mn2RhSb, the moments of Mn (A) and Mn (B) are antiparallel to each other. The total magnetic moments of the three considered half-metals assume integral values in a wide range of equilibrium lattice parameters.

Incorporation of Mn inAlxGa1−xNprobed by x-ray absorption and emission spectroscopy, high-resolution microscopy, x-ray diffraction, and first-principles calculations

Synchrotron radiation x-ray absorption and emission spectroscopy techniques, complemented by high-resolution transmission electron microscopy methods and density functional theory calculations are employed to investigate the effect of Mn in Al$_{x}$Ga$_{1-x}$N:Mn samples with an Al content up to 100%. The atomic and electronic structure of Mn is established together with its local environment and valence state. A dilute alloy without precipitation is obtained for Al$_{x}$Ga$_{1-x}$N:Mn with Al concentrations up to 82%, and the surfactant role of Mn in the epitaxial process is confirmed.

Magneto-optical spectrum and the effective excitonic Zeeman splitting energies of Mn and Co-doped CdSe nanowires

The electronic structure of Mn and Co-doped CdSe nanowires are calculated based on the six-band k·p effective-mass theory. Through the calculation, it is found that the splitting energies of the degenerate hole states in Mn-doped CdSe nanowires are larger than that in Co-doped CdSe nanowires when the concentration of these two kinds of magnetic ions is the same. In order to analysis the magneto-optical spectrum of Mn and Co-doped CdSe nanowires, the four lowest electron states and the four highest hole states are sorted when the magnetic field is applied, and the 10 lowest optical transitions between the conduction subbands and the valence subbands at the Γ point in Mn and Co-doped CdSe nanowires are shown in the paper, it is found that the order of the optical transitions at the Γ point almost do not change although two different kinds of magnetic ions are doped in CdSe nanowires. Finally, the effective excitonic Zeeman splitting energies at the Γ point are found to increase almost linearly with the increase of the concentration of the magnetic ions and the magnetic field; meanwhile, the giant positive effective excitonic g factors in Mn and Co-doped CdSe nanowires are predicted based on our theoretical calculation.

Elektroniese eienskappe van die Mn(asas)<sub>3</sub>-kompleks: 'n Sikliese voltammetrie- en berekeningschemiestudie

Electronic properties of Mn(acac)3 complex : a cyclic voltammetry and computational chemistry study Tris(acetylacetonato) Manganese(III) is a catalyst in alkyd paint. In this study, the electronic properties of Mn(acac)3 are determined by means of electrochemistry and computational chemistry. The optimised geometrical and electronic structure of Mn(acac)3 is calculated by means of computational chemistry, and electrochemistry is applied to measure the following reactions:MnIII(acac)3 - e- ⇆ MnIV(acac)3 MnIII(acac)3 + e- ⇆ MnII(acac)3

Magnetic Mn5Ge3 nanocrystals embedded in crystalline Ge: a magnet/semiconductor hybrid synthesized by ion implantation.

The integration of ferromagnetic Mn5Ge3 with the Ge matrix is promising for spin injection in a silicon-compatible geometry. In this paper, we report the preparation of magnetic Mn5Ge3 nanocrystals embedded inside the Ge matrix by Mn ion implantation at elevated temperature. By X-ray diffraction and transmission electron microscopy, we observe crystalline Mn5Ge3 with variable size depending on the Mn ion fluence. The electronic structure of Mn in Mn5Ge3 nanocrystals is a 3d6 configuration, which is the same as that in bulk Mn5Ge3. A large positive magnetoresistance has been observed at low temperatures. It can be explained by the conductivity inhomogeneity in the magnetic/semiconductor hybrid system.

Incorporation, valence state, and electronic structure of Mn and Cr in bulk single crystal β–Ga2O3

Single crystals of transition metal (TM) doped β–Ga2O3, a wide gap semiconductor system of interest for transparent conductive oxide and diluted magnetic semiconductor applications, have been studied in the dilute, non-interacting limit (≤0.06 cation %). Based on optical absorption, particle induced x-ray emission, and Rutherford backscattering measurements, Mn does not incorporate as well as Cr, and Mn degrades the crystal quality. Using superconducting quantum interference device (SQuID) magnetometry, a Brillouin type paramagnetic magnetization is observed for Mn or Cr doped crystals with an effective number of Bohr magnetons per TM ion of 5.88 ± 0.1 or 3.95 ± 0.1, respectively. A trace ferromagnetic signal is consistent with a very small concentration of secondary phases in the Mn-doped crystal. The position of the edge in x-ray absorption near edge structure (XANES) measurements suggests that the Cr takes the 3+ valence, while a mixture of Mn2+ and Mn3+ are present; based on the absence of a prominent pre-edge feature in the XANES, both TM predominantly occupy an octahedral site in β–Ga2O3. Density functional theory (DFT) results, optical absorption and SQuID data are consistent with this assignment. While the Cr-doped crystal is conductive, the Mn-doped crystal is insulating, which is consistent with the Mn2+/Mn3+ mixed valence, assuming the Fermi level is pinned mid-gap at the Mn 2+/3+ transition level, which is predicted by DFT to be 1.8 eV above the valence band maximum.

Surface atomic and electronic structure of Mn5Ge3on Ge(111)

The atomic and electronic structure of the Mn${}_{5}$Ge${}_{3}$(001) surface grown on Ge(111) $c$($2\ifmmode\times\else\texttimes\fi{}8$) has been studied in detail by angle-resolved photoelectron spectroscopy (ARPES), scanning tunneling microscopy (STM), and scanning tunneling spectroscopy. ARPES spectra recorded from the $\overline{\ensuremath{\Gamma}}$-$\overline{K}$-$\overline{M}$ and $\overline{\ensuremath{\Gamma}}$-$\overline{M}$-$\overline{\ensuremath{\Gamma}}$ directions of the surface Brillouin zone show six surface-related features. The STM images recorded at biases higher/lower than $\ifmmode\pm\else\textpm\fi{}$0.4 V always show a honeycomb pattern with two bright protrusions in each unit cell. At lower biases, a hexagonal, intermediate transition, and a honeycomb pattern are observed. These can be explained as arising from Mn and Ge atoms in the sublayer arranged in triangular structures and Mn atoms in the top layer arranged in a honeycomb structure, respectively. The photoemission and STM data from the germanide surface are discussed and compared to earlier published theoretical, photoelectron spectroscopy, and scanning tunneling microscopy studies.

Magnetism and electronic structure of Mn- and V-doped zinc blende ZnTe from first-principles calculations

By means of the first-principles full potential linearized augmented plane-wave method within the local density approximation for the exchange-correlation functional, we have investigated the magnetism and electronic structure of Mn- and V-doped zinc blende ZnTe. Total energy calculations show that, for high doping concentration (12.5%), ZnTe:Mn has an antiferromagnetic ground state while the ferromagnetic state is more favorable than the antiferromagnetic state for ZnTe:V. Furthermore, ZnTe with a low doping of Mn (6.25%) has a stable ferromagnetic ground state, which is in agreement with the experimental results. The calculated magnetic moment of ZnTe doped with Mn (V) mainly originates from transition metal Mn (V) atom with a little contribution from Te atom due to the hybridization between Mn (V) 3d and Te 5p electrons. Electronic structure indicates that Mn-doped ZnTe is a semiconductor, but V-doped ZnTe shows a half-metallic characteristic. We also discuss the difference between electronic and magnetic properties for ZnTe doped with 12.5% and 6.25% Mn.

Electronic structure of Mn in (Zn, Mn)O probed by resonant X-ray emission spectroscopy

The electronic structure of Mn in (Zn, Mn)O with different Mn concentrations has been investigated using resonant X-ray emission spectroscopy (RXES). The Mn L 2 , 3 RXES spectra reveal different spectral features depending on the resonant excitation energies and Mn concentrations. The surface dd excitations at about −1.9 eV of energy loss are identified in the highest Mn-doped sample. The comparison of integral intensity ratio of Mn L 2 to L 3 emission lines for these samples suggests that ferromagnetic samples have a large amount of free charge carriers, which are under consideration for the origin of ferromagnetism, with respect to antiferromagnetic ones.

Electronic structure of substitutional Mn in epitaxial In0.965Mn0.035Sb film

The magnetic and electronic structure of Mn in In0.965Mn0.035Sb ferromagnetic semiconductor thin film was studied by x-ray absorption spectroscopy and x-ray magnetic circular dichroism. Comparison with atomic multiplet calculations suggests that manganese substitutes on sites with tetrahedral symmetry. Strong magnetic dichroism was observed from 5 to 300 K, at an applied field of 2 T. The temperature dependence of dichroism indicates presence of two magnetic Mn species having very similar spectral features. A high temperature species dominates the dichroic response over 50–300 K and a low temperature species is observed below 50 K.

Manganese Borohydride As a Hydrogen-Storage Candidate: First-Principles Crystal Structure and Thermodynamic Properties

Manganese borohydride (Mn(BH4)2) is considered to be a high-capacity (∼10 wt %) solid-state hydrogen storage candidate, but so far has not been shown to exhibit reversible hydrogenation. This study presents the calculated crystal structure and electronic structure of Mn(BH4)2 from density-functional theory within the generalized gradient approximation and thermodynamic properties from the direct method lattice dynamics. A thermodynamically stable phase of Mn(BH4)2 is identified. The calculation of Gibbs energy at finite temperatures suggests that the stable phase is of I4̅m2 symmetry. The formation energy of Mn(BH4)2 for the I4̅m2 symmetry solid is −28.93 kJ/f.u. at 0 K including zero-point energy corrections, and the standard state enthalpy of formation is predicted to be −58.89 kJ/f.u. The most feasible dehydrogenation reaction is found to be Mn(BH4)2 = Mn + 2B+ 4H2, which is an endothermic reaction at decomposition temperature. The spin-polarized electronic density of states shows that manganese borohydride has a half-metallic nature due to the presence of half-filled 3d electrons from Mn. The electronic structure calculations and analysis show that the interaction between Mn atoms and BH4 complexes has an ionic character, while the internal bonding of BH4 is essentially covalent.

X-ray absorption study of the electronic structure of Mn-doped amorphous Si

The electronic structure of Mn in amorphous Si (a-MnxSi1−x) is studied by x-ray absorption spectroscopy at the Mn L3,2 edges for x=0.005−0.18. Except for the x=0.005 sample, which shows a slight signature of Mn2+ atomic multiplets associated with a local Mn moment, all samples have broad and featureless L3,2 absorption peaks, corresponding to an itinerant state for all 3d electrons. The broad x-ray absorption spectra exclude the possibility of a localized 3d moment and explain the unexpectedly quenched Mn moment in this magnetically doped amorphous semiconductor. Such a fully delocalized d state of Mn dopant in Si has not been previously suggested.

Growth and electronic structure of Mn on Al(1 1 1)

Growth and electronic structure of a 3d transition metal Mn on a free-electron-like metal Al(1 1 1) have been studied by photoelectron spectroscopy and low energy electron diffraction (LEED). A ( 3 × 3 ) R 30 ° LEED is observed at 6 ML Mn coverage, that is related to the α phase of bulk Mn. From the intensity of the adlayer and substrate core-level peaks and angle dependent studies, evidence of primarily layer by layer growth is observed. The Mn 2p core-level for 0.1 ML Mn coverage appears at 0.3 eV lower binding energy with respect to bulk Mn. With increasing Mn coverage, the Mn 2p binding energy increases. An extra component is observed at the lower binding energy side of the Al 2p spectra, that is related to interface alloying. The asymmetric line-shape of bulk-like Mn becomes symmetric for lower Mn coverages.

EPR and HYSCORE investigation of the electronic structure of the model complex Mn(imidazole) 6: Exploring Mn(II)–imidazole binding using single crystals

The electronic structure of the Mn(II)-imidazole binding was studied by EPR spectroscopy using the model complex Mn(Im) 6 diluted in a single crystal of Zn(Im) 6Cl 2·4(H 2O). The second rank zero-field splitting (ZFS) tensor ( D tensor) of the two sites, a and b, present in the crystal was determined by measuring the orientation patterns of the echo-detected EPR spectra in three different planes at 10 K ( D a = −106, D b = −118, E a = −17, E b = −22 × 10 −4 cm −1. Euler angles with respect to the crystal habitus: α a = 13°, β a = 76°, γ a = 108.5°, α b = 14°, β b = 73.5°, γ b = 103.5°). The contribution of cubic ZFS terms to the spectrum allowed us to determine the orientation of the N–Mn–N directions of the complex as well (Euler angles in the D tensor reference frame α = 100°, β = 23°, γ = 0°, both centers having the same orientation). The hyperfine interactions with 14N were explored by HYSCORE spectroscopy. The correlation patterns and modulation amplitudes in the 2D experiments were studied for different electron spin transitions and orientations of the crystal. Signals of three different pairs of nitrogens were found. The results were analyzed considering that the N–Mn binding directions are principal directions of the hyperfine and nuclear quadrupole tensor of 14N. All three pairs of nitrogens were found to be almost equivalent with an isotropic contribution of A iso ≈ 3.2 MHz and an almost axial anisotropic coupling of 2 T ≈ 1.1 MHz along the N–Mn bonding direction. The nuclear quadrupole principal values are 1.5 MHz along the bonding direction, −0.6 MHz in the direction perpendicular to the imidazole plane, and −0.9 MHz in the direction perpendicular to both.

The electronic structure of Mn in oxides, coordination complexes, and the oxygen-evolving complex of photosystem II studied by resonant inelastic X-ray scattering.

Resonant inelastic X-ray scattering (RIXS) was used to collect Mn K pre-edge spectra and to study the electronic structure in oxides, molecular coordination complexes, as well as the S1 and S2 states of the oxygen-evolving complex (OEC) of photosystem II (PS II). The RIXS data yield two-dimensional plots that can be interpreted along the incident (absorption) energy or the energy transfer axis. The second energy dimension separates the pre-edge (predominantly 1s to 3d transitions) from the main K-edge, and a detailed analysis is thus possible. The 1s2p RIXS final-state electron configuration along the energy transfer axis is identical to conventional L-edge absorption spectroscopy, and the RIXS spectra are therefore sensitive to the Mn spin state. This new technique thus yields information on the electronic structure that is not accessible in conventional K-edge absorption spectroscopy. The line splittings can be understood within a ligand field multiplet model, i.e., (3d,3d) and (2p,3d) two-electron interactions are crucial to describe the spectral shapes in all systems. We propose to explain the shift of the K pre-edge absorption energy upon Mn oxidation in terms of the effective number of 3d electrons (fractional 3d orbital population). The spectral changes in the Mn 1s2p(3/2) RIXS spectra between the PS II S1 and S2 states are small compared to that of the oxides and two of the coordination complexes (Mn(III)(acac)3 and Mn(IV)(sal)2(bipy)). We conclude that the electron in the step from S1 to S2 is transferred from a strongly delocalized orbital.