arXiv subjects

Yu. S. Dedkov

Publications and source records attributed to Yu. S. Dedkov.

29 records · Page 2Linked to original sources

arXiv2010

Induced magnetism of carbon atoms at the graphene/Ni(111) interface

We report an element-specific investigation of electronic and magnetic properties of the graphene/Ni(111) system. Using magnetic circular dichroism, the occurrence of an induced magnetic moment of the carbon atoms in the graphene layer aligned parallel to the Ni 3d magnetization 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 $0.05-0.1 μ_B$ per atom.

cond-mat.mtrl-sci↗

arXiv2009

Preparation and photoemission investigation of bulk-like a-Mn films on W(110)

We report the successful stabilization of a thick bulk-like, distorted $α$-Mn film with (110) orientation on a W(110) substrate. The observed $(3\times3)$ overstructure for the Mn film with respect to the original W(110) low-energy electron diffraction pattern is consistent with the presented structure model. The possibility to stabilize such a pseudomorphic Mn film is supported by density functional total energy calculations. Angle-resolved photoemission spectra of the stabilized $α$-Mn(110) film show weak dispersions of the valence band electronic states in accordance with the large unit cell.

cond-mat.mtrl-sci↗

arXiv2008

Graphene/Ni(111) System: Spin- and Angle-Resolved Photoemission Studies

Here we report spin- and angle-resolved photoemission studies of the inert graphene layer formed on the surface of a ferromagnetic material, Ni(111). X-ray photoemission and spin-resolved spectroscopy of secondary electrons reveal that graphene behaves like a protection layer on the Ni(111) surface preventing its reaction with adsorbed oxygen. Angle-resolved photoelectron spectroscopy of $π$ states of graphene on Ni(111) shows a strong dependence of binding energy of these states on the direction of magnetization of the sample. We conclude that the observed extraordinary high "splitting" up to 225 meV of the $π$ band in the graphene layer is a manifes-tation of the Rashba effect which provides a direct possibility to a flexible control of an electron spin in a graphene-based spin-FET.

cond-mat.mtrl-sci↗

arXiv2008

Dispersion of a single $4f$ impurity state in photoemission spectra of Yb/W(110)

Angle-resolved photoemission spectra of a monolayer of Yb on W(110) reveal energy splittings and dispersion of the Yb 4f states that are obviously due to their hybridization with W-derived valence bands. These effects occur at well defined points of the surface Brillouin zone although a smearing over reciprocal space is expected from the structural incoherence of the Yb and W lattices. We conclude therefore that dispersion is not related to the periodic arrangement of the $4f$ states but reflects the k-dependent interaction of a single Yb 4f impurity with W bands.

cond-mat.str-el↗

arXiv2008

Graphene-protected iron layer on Ni(111)

Here we report the photoemission studies of intercalation process of Fe underneath graphene layer on Ni(111). The process of intercalation was monitored via XPS of corresponding core levels and UPS of the graphene-derived $π$ states in the valence band. \textit{fcc}-Fe films with thickness of 2-5 monolayers at the interface between graphene and Ni(111) form epitaxial magnetic layer passivated from the reactive environment, like for example oxygen gas.

cond-mat.mtrl-sci↗

arXiv2007

Rashba effect in the graphene/Ni(111) system

Here, we report on angle-resolved photoemission studies of the electronic $π$ states of high-quality epitaxial graphene layer on a Ni(111) surface. In this system electron binding energy of the $π$ states shows a strong dependence on the magnetization reversal of the Ni film. The observed extraordinary large energy shift up to 225 meV of the graphene-derived $π$-band peak position for opposite magnetization directions is attributed to a manifestation of the Rashba interaction of spin-polarized electrons in the $π$ band with the large effective electric field at graphene/Ni interface. Our findings show that an electron spin in the graphene layer can be manipulated in a controlled way and have important implications for graphene-based spintronic devices.

cond-mat.mtrl-sci↗

arXiv2007

Method of measurements with random perturbation: Application in photoemission experiments

We report an application of a simultaneous perturbation stochastic approximation (SPSA) algorithm to filtering systematic noise (SN) with non-zero mean value in photoemission data. In our analysis we have used a series of 50 single-scan photoemission spectra of W(110) surface where randomly chosen SN was added. It was found that the SPSA-evaluated spectrum is in good agreement with the spectrum measured without SN. On the basis of our results a wide application of SPSA for evaluation of experimental data is anticipated.

math-ph↗

arXiv2007

A possible source of spin-polarized electrons: The inert graphene/Ni(111) system

We report on an investigation of spin-polarized secondary electron emission from the chemically inert system: graphene/Ni(111). An ordered passivated graphene layer (monolayer of graphite, MG) was formed on Ni(111) surface via cracking of propylene gas. The spin-polarization of the 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.

cond-mat.mtrl-sci↗

arXiv2007

Spin-dependence of Ce $4f$ hybridization in magnetically ordered systems: A spin-resolved photoemission study of Ce/Fe(110)

Spin- and angle-resolved resonant (Ce $4d\to4f$) photoemission spectra of a monolayer Ce on Fe(110) reveal spin-dependent changes of the Fermi-level peak intensities. That indicate a spin-dependence of $4f$ hybridization and, thus, of $4f$ occupancy and local moment. The phenomenon is described in the framework of the periodic Anderson model by $4f$ electron hopping into the exchange split Fe 3d derived bands that form a spin-gap at the Fermi energy around the $\barΓ$ point of the surface Brillouin zone.

cond-mat.str-el↗

arXiv2004

Growth and spin-resolved photoelectron spectroscopy of the MgO/Fe(110) system

Electronic and structural properties of ultrathin MgO layers grown on epitaxial Fe(110) films were investigated at room temperature by means of spin-resolved photoelectron spectroscopy, Auger-electron spectroscopy, and low energy electron diffraction. The spin polarization at the Fermi level of the Fe(110) film decreases abruptly with increasing thickness of MgO layer up to 7 Å. This behavior is attributed to the formation of a thin FeO layer at the MgO(111)/Fe(110) interface, attenuating the intrinsic spin polarization.

cond-mat.mtrl-sci↗

arXiv2003

Modification of the valence band electronic structure under Ag intercalation underneath graphite monolayer on Ni(111)

Angle-resolved photoemission spectroscopy and Auger electron spectroscopy have been applied to study the intercalation process of silver underneath a monolayer of graphite (MG) on Ni(111). The room-temperature deposition of silver on top of MG/Ni(111) system leads to the islands-like growth of Ag on top of the MG. Annealing of the "as-deposited" system at temperature of 350-450 C results in the intercalation of about 1-2 ML of Ag underneath MG on Ni(111) independently of the thickness of pre-deposited Ag film (3-100 A). The intercalation of Ag is followed by a shift of the graphite-derived valence band states towards energies which are slightly larger than ones characteristic for pristine graphite. This observation is understood in terms of a weakening of chemical bonding between the MG and the substrate in the MG/Ag/Ni(111) system with a small MG/Ni(111) covalent contribution to this interaction.

cond-mat.mtrl-sci↗