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Full-Text Articles in Physics
Effect Of Gadolinium Doping On The Electronic Band Structure Of Europium Oxide, Juan Colon Santana, Joonhee Michael An, Ning Wu, Kirill D. Belashchenko, Xianjie Wang, Pan Liu, Jinke Tang, Yaroslav B. Losovyj, I. N. Yakovkin, Peter A. Dowben
Effect Of Gadolinium Doping On The Electronic Band Structure Of Europium Oxide, Juan Colon Santana, Joonhee Michael An, Ning Wu, Kirill D. Belashchenko, Xianjie Wang, Pan Liu, Jinke Tang, Yaroslav B. Losovyj, I. N. Yakovkin, Peter A. Dowben
Ning Wu
High quality films of EuO and Eu0.96Gd0.04O were grown on p-type Si(100) via pulsed laser deposition. X-raydiffraction results show that the addition of Gd changes the growth texture from [001] to [111]. Angular-resolved photoemission spectroscopy reveals electron pockets around the X points in Gd-doped EuO, indicating that the band gap in EuO is indirect. Combined photoemission and inverse photoemission measurements showan apparent transition from n-type to p-type behavior, which is likely due to band bending near the polar (111) surface.
When Measured Spin Polarization Is Not Spin Polarization, Peter Dowben, Ning Wu, Christian Binek
When Measured Spin Polarization Is Not Spin Polarization, Peter Dowben, Ning Wu, Christian Binek
Ning Wu
Spin polarization is an unusually ambiguous scientific idiom and, as such, is rarely well defined. A given experimental methodology may allow one to quantify a spin polarization but only in its particular context. As one might expect, these ambiguities sometimes give rise to inappropriate interpretations when comparing the spin polarizations determined through different methods. The spin polarization of CrO2 and Cr2O3 illustrate some of the complications which hinders comparisons of spin polarization values.
Imaging And Control Of Surface Magnetization Domains In A Magnetoelectric Antiferromagnet, Ning Wu, Xi He, Aleksander Wysocki, Uday Lanke, Takashi Komesu, Kirill Belashchenko, Christian Binek, Peter Dowben
Imaging And Control Of Surface Magnetization Domains In A Magnetoelectric Antiferromagnet, Ning Wu, Xi He, Aleksander Wysocki, Uday Lanke, Takashi Komesu, Kirill Belashchenko, Christian Binek, Peter Dowben
Ning Wu
We report the direct observation of surface magnetization domains of the magnetoelectric Cr2O3 using photoemission electron microscopy with magnetic circular dichroism contrast and magnetic force microscopy. The domain pattern is strongly affected by the applied electric field conditions. Zero-field cooling results in an equal representation of the two domain types, while electric-field cooling selects one dominant domain type. These observations confirm the existence of surface magnetization, required by symmetry in magnetoelectric antiferromagnets.
When Measured Spin Polarization Is Not Spin Polarization, Peter A. Dowben, Ning Wu, Christian Binek
When Measured Spin Polarization Is Not Spin Polarization, Peter A. Dowben, Ning Wu, Christian Binek
Ning Wu
Spin polarization is an unusually ambiguous scientific idiom and, as such, is rarely well defined. A given experimental methodology may allow one to quantify a spin polarization but only in its particular context. As one might expect, these ambiguities sometimes give rise to inappropriate interpretations when comparing the spin polarizations determined through different methods. The spin polarization of CrO2 and Cr2O3 illustrate some of the complications which hinders comparisons of spin polarization values.
The Minority Spin Surface Bands Of Cos2(001), Ning Wu, Renat F. Sabirianov, Wai-Ning Mei, Yaroslav B. Losovyj, N. Lozova, M. Manno, C. Leighton, Peter A. Dowben
The Minority Spin Surface Bands Of Cos2(001), Ning Wu, Renat F. Sabirianov, Wai-Ning Mei, Yaroslav B. Losovyj, N. Lozova, M. Manno, C. Leighton, Peter A. Dowben
Ning Wu
Angle-resolved photoemission was used to study the surface electronic band structure of high quality single crystals of ferromagnetic CoS2 (below 120 K). Strongly dispersing Co t2g bands are identified along the (100) k ǁ direction, the Γ-X line of the surface Brillouin zone, in agreement with model calculations. The calculated surface band structure includes corrections for the previously determined surface structure of CoS2(001) and is in general agreement with the experimental photoemission spectra in the region of the Fermi level. There is evidence of the existence of several minority spin surface states, falling into a gap of the projected minority …
Radiation-Induced Decomposition Of The Metal-Organic Molecule Bis(4-Cyano-2,2,6,6-Tetramethyl-3,5-Heptanedionato)Copper(Ii), David Wisbey, Ning Wu, Yaroslav B. Losovyj, Ihor Ketsman, A. N. Caruso, Danqin Feng, John Belot, Elio Vescovo, Peter A. Dowben
Radiation-Induced Decomposition Of The Metal-Organic Molecule Bis(4-Cyano-2,2,6,6-Tetramethyl-3,5-Heptanedionato)Copper(Ii), David Wisbey, Ning Wu, Yaroslav B. Losovyj, Ihor Ketsman, A. N. Caruso, Danqin Feng, John Belot, Elio Vescovo, Peter A. Dowben
Ning Wu
The effects of vacuum ultraviolet radiation on the adsorbed copper center molecule bis(4-cyano-2,2,6,6- tetramethyl-3,5-heptanedionato)copper(II) (or Cu(CNdpm)2), (C24H36N2O4Cu, Cu(II)) was studied by photoemission spectroscopy. Changes in the ultraviolet photoemission spectra (UPS) of Cu(CNdpm)2, adsorbed on Co(1 1 1), indicate that the ultraviolet radiation leads to decomposition of Cu(CNdpm)2 and this decomposition is initially dominated by loss of peripheral hydrogen.
Induced Spin Polarization Of Copper Spin 1/2 Molecular Layers, David Wisbey, Ning Wu, Danqin Feng, A. N. Caruso, J. Belot, Yaroslav B. Losovyj, Elio Vescovo, Peter A. Dowben
Induced Spin Polarization Of Copper Spin 1/2 Molecular Layers, David Wisbey, Ning Wu, Danqin Feng, A. N. Caruso, J. Belot, Yaroslav B. Losovyj, Elio Vescovo, Peter A. Dowben
Ning Wu
Thin films of the metal organic molecule bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) (or Cu(CNdpm)2), (C24H36N2O4Cu, Cu(II)), deposited on ferromagnetic Co(111) at 40 K, exhibit a finite electron spin polarization. The spin polarization magnitude and sign for Cu(CNdpm)2 deposited on Co(111) is coverage dependent, but deviates from the mean field expectations for a simple paramagnet on a ferromagnetic substrate. The spin asymmetry is seen to favor select molecular orbitals, consistent with the predicted single molecule density of states. The overlayer polarization observed indicates a strong influence of the ferromagnetic Co(111) substrate and some extra-molecular magnetic coupling.
Interface-Induced Spin And Dipole Ordering Of The Copper Spin ½ Molecule: Bis(4-Cyano-2,2,6,6-Tetramethyl-3,5-Heptanedionato)Copper(Ii), David Wisbey, Ning Wu, Danqin Feng, Anthony N. Caruso, John Belot, Yaroslav B. Losovyj, Elio Vescovo, Peter A. Dowben
Interface-Induced Spin And Dipole Ordering Of The Copper Spin ½ Molecule: Bis(4-Cyano-2,2,6,6-Tetramethyl-3,5-Heptanedionato)Copper(Ii), David Wisbey, Ning Wu, Danqin Feng, Anthony N. Caruso, John Belot, Yaroslav B. Losovyj, Elio Vescovo, Peter A. Dowben
Ning Wu
Using light-polarization-dependent angle-resolved photoemission, the metal-organic molecule bis(4-cyano- 2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) (or Cu(CNdpm)2, i.e., C24H36N2O4Cu, Cu(II)) is observed to adopt a preferential orientation that depends on the film thickness and substrate when adsorbed on Co(111) and Cu(111). In addition, the final-state binding energies change with film thickness, suggesting the substrates affect the screening or charging in the photoemission final state. For Cu(CNdpm)2 deposited on Co(111), the induced spin polarization was found to depend strongly on the molecular orbital contributions.
The Surface Relaxation And Band Structure Of Mo(112), Ning Wu, Yaroslav B. Losovyj, Zhaoxian Yu, Renat F. Sabirianov, Wai-Ning Mei, N. Lozova, J. A. Colón Santana, Peter A. Dowben
The Surface Relaxation And Band Structure Of Mo(112), Ning Wu, Yaroslav B. Losovyj, Zhaoxian Yu, Renat F. Sabirianov, Wai-Ning Mei, N. Lozova, J. A. Colón Santana, Peter A. Dowben
Ning Wu
The experimental and theoretical surface band structures of Mo(112) are compared. This surface band structure mapping is presented with corrections included for the lattice relaxation of the Mo(112) surface. Quantitative low energy electron diffraction (LEED) has been used to determine the details of the Mo(112) surface structure. The first layer contraction is 14.9% by LEED intensity versus voltage analysis and is in general agreement with the 17.6% contraction found from total surface energy optimization. The electronic band structure is mapped out along Γ-X and Γ–Y of the surface Brillouin zone (SBZ). There is strong evidence of electron–phonon coupling particularly in …
Corrigendum, Re: The Structure Of The Cos2 (100)-(1×1) Surface, Z. X. Yu, M. A. Van Hove, S. Y. Tong, David Wisbey, Yaroslav B. Losovyj, Ning Wu, M. Manno, L. Wang, C. Leighton, Wai-Ning Mei, Peter A. Dowben
Corrigendum, Re: The Structure Of The Cos2 (100)-(1×1) Surface, Z. X. Yu, M. A. Van Hove, S. Y. Tong, David Wisbey, Yaroslav B. Losovyj, Ning Wu, M. Manno, L. Wang, C. Leighton, Wai-Ning Mei, Peter A. Dowben
Ning Wu
Different surface terminations have been previously discussed in reference [12] of J. Phys.: Condens. Matter 19 156223 (i.e., Ying Jiu Jin and Jae Il Lee 2006 Phys. Rev. B 73 064405) and we inadvertently failed to properly cite this reference in the attribution of figure 3 of our paper.
Surface Segregation In Multicomponent Clusters, Peter A. Dowben, Ning Wu, Natalie Palina, R. Müller, J. Hormes, Yaroslav B. Losovyj
Surface Segregation In Multicomponent Clusters, Peter A. Dowben, Ning Wu, Natalie Palina, R. Müller, J. Hormes, Yaroslav B. Losovyj
Ning Wu
Nanostructured materials are not immune from surface segregation, as can be shown for solid samples made from nanosized BaFe12–2xCoxTixO19 barium ferrite particles and a variety of free clusters. Both theory and experiment provide ample demonstration that very limited dimensions of very small clusters does not necessarily impart stability against surface and grain boundary segregation. In fact, with the larger surface to volume ratio in small clusters and lower average atomic coordination, we anticipate that compositional instabilities in small clusters will readily occur.
The Structure Of The Cos2 (100)-(1 × 1) Surface, Z. X. Yu, M. A. Van Hove, S. Y. Tong, David Wisbey, Yaroslav B. Losovyj, Ning Wu, M. Manno, L. Wang, C. Leighton, Wai-Ning Mei, Peter A. Dowben
The Structure Of The Cos2 (100)-(1 × 1) Surface, Z. X. Yu, M. A. Van Hove, S. Y. Tong, David Wisbey, Yaroslav B. Losovyj, Ning Wu, M. Manno, L. Wang, C. Leighton, Wai-Ning Mei, Peter A. Dowben
Ning Wu
Quantitative low-energy electron diffraction (LEED) has been used to determine the structure of the cubic CoS2 (100)-(1 × 1) surface. The clearly favored structural model from the LEED analysis is the 1S-terminated (1 × 1) surface, in which the S–S dimer is intact and the terminal surface layer retains a complete S–Co–S sandwich structure. The surface S atoms move outwards towards the vacuum while the subsurface Co atoms move towards the bulk, by approximately 0.03 and 0.11 Å, respectively. In addition, the S atoms in the third sublayer relax outwards by about 0.12 Å, thus providing an indication of a …
Correlation Effects And Electronic Structure Of Gd@C60, Renat F. Sabirianov, Wai-Ning Mei, Jing Lu, Yi Gao, Xiao Cheng Zeng, R. D. Bolskar, P. Jeppson, Ning Wu, A. N. Caruso, Peter A. Dowben
Correlation Effects And Electronic Structure Of Gd@C60, Renat F. Sabirianov, Wai-Ning Mei, Jing Lu, Yi Gao, Xiao Cheng Zeng, R. D. Bolskar, P. Jeppson, Ning Wu, A. N. Caruso, Peter A. Dowben
Ning Wu
We have investigated the electronic structure of Gd@C60 using ab initio calculations, photoemission and resonant photoemission (constant initial state spectroscopy). In comparing our calculations based on the local spin density approximation and the Hubbard model description with the observed photoemission spectra, we conclude that Gd 4f states exhibit enhanced correlation energies. These correlation energies have values larger than those normally observed in metallic gadolinium and gadolinium compounds. We attributed the enhanced correlation to the diminished screening of the encapsulated Gd. Both calculation and experiment confirm a strong hybridization between the valence states of Gd and the C 2p states of …
The Surface Stability Of Cos2(100), Ning Wu, Renat F. Sabirianov, Chun-Gang Duan, Wai-Ning Mei, David Wisbey, Yaroslav B. Losovyj, M. Manno, C. Leighton, En Cai, Jiandi Zhang, Peter A. Dowben
The Surface Stability Of Cos2(100), Ning Wu, Renat F. Sabirianov, Chun-Gang Duan, Wai-Ning Mei, David Wisbey, Yaroslav B. Losovyj, M. Manno, C. Leighton, En Cai, Jiandi Zhang, Peter A. Dowben
Ning Wu
The stability of various possible terminations of the CoS2 (1 × 1) surface have been explored and theoretical expectations are found to agree with experiment. With extensive annealing, there is a phase separation at the (100) surface of CoS2. Sulfur segregation to the surface leads to a significant change in the largely sulfur bands due to changes in the hybridized bands, with cobalt. Resonant photoemission spectra indicate clearly that the hybridized cobalt and sulfur bands, characteristic of the CoS2 bulk, lie at higher binding energies than those of segregated sulfur layers. This is discussed in terms of the stability of …
Imaging And Control Of Surface Magnetization Domains In A Magnetoelectric Antiferromagnet, Ning Wu, Xi He, Aleksander L. Wysocki, Uday Lanke, Takashi Komesu, Kirill D. Belashchenko, Christian Binek, Peter A. Dowben
Imaging And Control Of Surface Magnetization Domains In A Magnetoelectric Antiferromagnet, Ning Wu, Xi He, Aleksander L. Wysocki, Uday Lanke, Takashi Komesu, Kirill D. Belashchenko, Christian Binek, Peter A. Dowben
Ning Wu
We report the direct observation of surface magnetization domains of the magnetoelectric Cr2O3 using photoemission electron microscopy with magnetic circular dichroism contrast and magnetic force microscopy. The domain pattern is strongly affected by the applied electric field conditions. Zero-field cooling results in an equal representation of the two domain types, while electric-field cooling selects one dominant domain type. These observations confirm the existence of surface magnetization, required by symmetry in magnetoelectric antiferromagnets.
The Electronic Band Structure Of Cos2, Ning Wu, Yaroslav B. Losovyj, David Wisbey, Kirill D. Belashchenko, M. Manno, L. Wang, C. Leighton, Peter A. Dowben
The Electronic Band Structure Of Cos2, Ning Wu, Yaroslav B. Losovyj, David Wisbey, Kirill D. Belashchenko, M. Manno, L. Wang, C. Leighton, Peter A. Dowben
Ning Wu
Angle-resolved and energy-dependent photoemission was used to study the band structure of paramagnetic CoS2 from high-quality single-crystal samples. A strongly dispersing hybridized Co–S band is identified along the Γ–X line. Fermi level crossings are also analyzed along this line, and the results are interpreted using band structure calculations. The Fermi level crossings are very sensitive to the separation in the S–S dimer, and it is suggested that the half-metallic gap in CoS2 may be controlled by the bonding– antibonding splitting in this dimer, rather than by exchange splitting on the Co atoms.