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Here we present a study of the electronic structure of epitaxial ferromagnetic Mn5Ge3(0001) films on Ge(111) by means of x-ray absorption spectroscopy, x-ray photoelectron spectroscopy, and spin-resolved photoelectron spectroscopy. Spin-polarization (P) value of +(15±5)% at the Fermi energy (EF) is measured with a photon energy of hν=21.2 eV. Our findings are in contrast to recent band structure calculations, predicting P=-41% at EF for the ferromagnetic bulk Mn5Ge3. [ABSTRACT FROM AUTHOR]

We report on a detailed study of structural, magnetic, and electronic properties of MnxGe1-x single crystals (011Ge8 reference sample as well as to those of the highly inhomogeneous Mn-rich parts of the sample. X-ray absorption spectroscopy (XAS) at the Mn L2,3 absorption edge shows that Mn ions in Mn-rich and Mn-poor parts are in the divalent high-spin state. Resonant valence-band photoelectron spectroscopy (ResPES) was performed at the Mn 2p3/2 absorption edge for the Mn-poor part. The obtained Mn 3d PDOS shows a feature centered at 4.8 eV which is characteristic for the Mn5Ge3 phase. We identify the formation of ferromagnetic intermetallic compounds as the most possible origin of ferromagnetism in both Mn-rich and Mn-poor regions of the MnxGe1-x samples. [ABSTRACT FROM AUTHOR]

We present a detailed study on the structural, magnetic, and optical properties, as well as the electronic structure of epitaxial Co-doped ZnO films prepared by magnetron sputtering. Different preparation conditions were implemented in order to control the concentration of oxygen vacancies in the ZnO host lattice. Magnetization measurements indicate ferromagnetic behavior at low temperature for samples prepared at oxygen-poor conditions whereas the samples prepared at oxygen-rich conditions show extremely small ferromagnetic signal corroborating that ferromagnetism in Zn1-xCoxO correlates with the presence of the oxygen-related defects. X-ray absorption spectroscopy (XAS) at the Co L2, 3 edge together with optical transmittance measurements show that Co ions are present in the high-spin Co2+ (d7) state under tetrahedral symmetry indicating a proper incorporation in the ZnO host lattice. Comparison of the O K edge XAS spectra of the samples prepared at different conditions show substantial changes in the spectral line shape which are attributed to the presence of lattice defects such as oxygen vacancies in the ferromagnetic oxygen-poor Co-doped ZnO samples. Our findings indicate that the ferromagnetic properties of Co-doped ZnO samples are strongly correlated with the presence of oxygen vacancies in the ZnO lattice supporting the spin-split impurity band model. [ABSTRACT FROM AUTHOR]

Fe(110) films were epitaxially grown on sapphire substrates using a Mo(110) buffer layer in an ultrahigh-vacuum molecular-beam epitaxy system. The magnetic properties were examined ex situ by Brillouin light scattering and superconducting quantum interference device magnetometry. To determine the magnetic anisotropy constants the frequency of the Damon-Eshbach [J. Phys. Chem. Solids 19, 308 (1961)] surface spin-wave mode was measured as a function of the in-plane angle between the external magnetic field and the Fe[001] crystal axis. The angle-dependent frequency was fitted by a spin-wave model. We found that the easy axis of the cubic magnetocrystalline anisotropy K1 and an additional uniaxial in-plane anisotropy K∥(2) are aligned parallel to the in-plane Fe[001] axis for Fe-layer thicknesses from 0.8 to 37 nm, with K1 increasing and K∥(2) decreasing with increasing Fe thickness. Possible origins of the observed uniaxial anisotropy are discussed. [ABSTRACT FROM AUTHOR]

We present systematic investigations of the electronic and magnetic properties of the graphene/ Ni(111) system by means of x-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD) at the Ni L2,3 and C K absorption edges. The XAS C 1s→π* ,σ* spectra show dramatic changes as the angle, α, between the electrical vector of light and normal of the sample is varied reflecting the symmetry of the final state (σ or π). XMCD spectra reveal an induced magnetic moment of the carbon atoms in the graphene layer. Our experimental results are discussed in the light of previous results on the observation of induced magnetism in nonmagnetic materials. [ABSTRACT FROM AUTHOR]

The authors report on a scanning tunneling microscopy/spectroscopy investigation of the possibility to influence the assembly of monolayers of Mn12 single molecule magnets on a functionalized Au(111) surface by using flexible linker molecules. The results corroborate the general suitability of the deposition via ligand exchange reaction but, on the other hand, reveal the need for a compromise between conductivity and flexibility of the linker molecules. The results are discussed with respect to previous attempts [A. Naitabdi et al., Adv. Mater. (Weinheim, Ger.) 17, 1612 (2005)] to deposit ordered monolayers of Mn12 molecules on Au(111). [ABSTRACT FROM AUTHOR]

The electronic and crystallographic structure of the graphene/Rh(111) moiré lattice is studied via combination of density-functional theory calculations and scanning tunneling and atomic force microscopy (STM and AFM). Whereas the principal contrast between hills and valleys observed in STM does not depend on the sign of applied bias voltage, the contrast in atomically resolved AFM images strongly depends on the frequency shift of the oscillating AFM tip. The obtained results demonstrate the perspectives of application atomic force microscopy/spectroscopy for the probing of the chemical contrast at the surface. [ABSTRACT FROM AUTHOR]

Regularly sized Ni nanoclusters (NCs) have been grown on a graphene Moiré on Rh(111). Using scanning tunneling microscopy, we determine that initial growth of Ni at 150 K leads to preferential nucleation of monodispersed NCs at specific sites of the Moiré superstructure. However, a defined long-range ordering of NCs with increasing coverage is not observed. Room temperature Ni deposition leads to the formation of flat triangular-shaped islands which are well-matched to the Moiré registry. [ABSTRACT FROM AUTHOR]

We report an element-specific investigation of electronic and magnetic properties of the graphene/Ni(111) system. Using x-ray magnetic circular dichroism, the occurrence of an induced magnetism of the carbon atoms in the graphene layer is observed. We attribute this magnetic moment to the strong hybridization between C π and Ni 3d valence band states. The net magnetic moment of carbon in the graphene layer is estimated to be in the range of 0.05–0.1 μB per atom. [ABSTRACT FROM AUTHOR]

Fully epitaxial Fe(110)/MgO(111)/Fe(110) magnetic tunnel junctions (MTJs) have been tested with respect to symmetry-enforced spin filtering. The Fe(110) electrodes exhibit Σ1↑ and Σ1↓ spin states, both crossing the Fermi level, but with a group velocity about 50% smaller for the minority states compared to the majority ones. These epitaxial but symmetry-mismatched MTJs yield tunneling magnetoresistance (TMR) values of 54% at 1.5 K and 28% at room temperature. The TMR value and the estimated tunneling spin polarization are consistent with a partial spin filtering due to the Σ1↑ states partially compensated by the Σ1↓ states. [ABSTRACT FROM AUTHOR]

Here we report a photoemission study of the Fe intercalation underneath a graphene layer on Ni(111). The process of intercalation was monitored by means of x-ray photoemission of corresponding core levels as well as ultraviolet photoemission of the graphene-derived π states in the valence band. Thin fcc Fe layers (2–5 ML thickness) at the interface between a graphene capping layer and Ni(111) form epitaxial films passivated from the reactive environment. [ABSTRACT FROM AUTHOR]

We report on an investigation of spin-polarized secondary electron emission from the chemically inert system: graphene/Ni(111). An ordered passivation graphene layer (monolayer of graphite) was formed on Ni(111) surface via cracking of propylene gas. The spin polarization of secondary electrons obtained from this system upon photoemission is only slightly lower than the one from the clean Ni surface but does not change upon large oxygen exposure. These results suggest to use such passivated Ni(111) surface as a source of spin-polarized electrons stable against adsorption of reactive gases. [ABSTRACT FROM AUTHOR]

The authors report on the electronic properties of individual molecules of two Mn12 derivatives chemically grafted on the functionalized Au(111) surface studied by means of ultrahigh vacuum scanning tunneling microscopy/spectroscopy at room temperature. Reproducible current-voltage curves were obtained from both Mn12 molecules, showing a well defined wide band gap. In agreement with the tunneling spectroscopy results, the bias voltage variation upon scanning leads to apparent height changes of the Mn12 clusters. The authors discuss these findings in the light of the recent band structure calculations and electronic transport measurements on single Mn12 molecules. [ABSTRACT FROM AUTHOR]

Magnetic domains and domain walls in epitaxial Fe3O4(100) elements (rings and wires) are imaged using magnetic force microscopy and photoemission electron microscopy. We show that the interplay between the four-fold magnetocrystalline anisotropy and the shape determines the equilibrium domain structure. Domain walls with a characteristic zig-zag structure are observed in Fe3O4(100) elements initially magnetized along one of the magnetocrystalline hard axes. We attribute the formation of zig-zag domain walls to the competition of the four-fold magnetocrystalline anisotropy, the exchange and dipolar coupling. A direct correlation between the wire width and the spin structure of zig-zag domain walls is found. [ABSTRACT FROM AUTHOR]

Electronic and structural properties of epitaxial ultrathin aluminum oxide layers grown on epitaxial Fe(110) films were investigated at room temperature by means of spin-, angle- and energy-resolved photoemission spectroscopy. A spin polarization of - ( 15±5)% near the Fermi energy E[sub F] is found for 1 (ML) of α-A1[sub 2]O[sub 3] on epitaxial Fe(110). This value results from the attenuation of -80% of Fe(110) by the oxide layer thickness and the spin-independent part of the scattering cross section. [ABSTRACT FROM AUTHOR]

A correction to the article "Nucleation and growth of nickel nanoclusters on graphene Moiré on Rh(111)" is presented.