Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 8 of 8
Full-Text Articles in Physics
Rare Earth Dopant (Nd, Gd, Dy, And Er) Hybridization In Lithium Tetraborate, Tony D. Kelly, James C. Petrosky, John W. Mcclory, Volodymyr T. Adamiv, Yaroslav V. Burak, Bohdan V. Padlyak, Ihor M. Teslyuk, Ning Liu, Lu Wang, Wai-Ning Mei, Peter A. Dowben
Rare Earth Dopant (Nd, Gd, Dy, And Er) Hybridization In Lithium Tetraborate, Tony D. Kelly, James C. Petrosky, John W. Mcclory, Volodymyr T. Adamiv, Yaroslav V. Burak, Bohdan V. Padlyak, Ihor M. Teslyuk, Ning Liu, Lu Wang, Wai-Ning Mei, Peter A. Dowben
Peter Dowben Publications
The four dopants (Nd, Gd, Dy, and Er) substitutionally occupy the Li+ sites in lithium tetra borate (Li2B407: RE) glasses as determined by analysis of the extended X-ray absorption fine structure. The dopants are coordinated by 6-8 oxygen at a distance of 2.3 to 2.5 A. depending on the rare earth. The inverse relationship between the RE-O coordination distance and rare earth (RE) atomic number is consistent with the expected lanthanide atomic radial contraction with increased atomic number. Through analysis of the X-ray absorption near edge structure, the rare earth dopants adopt the RE …
Spin Polarization Asymmetry At The Surface Of Chromia, Shi Cao, Xin Zhang, Ning Wu, A T. N'Diaye, G Chen, A K. Schmid, Xumin Chen, W Echtenkamp, Axel Enders, Christian Binek, Peter A. Dowben
Spin Polarization Asymmetry At The Surface Of Chromia, Shi Cao, Xin Zhang, Ning Wu, A T. N'Diaye, G Chen, A K. Schmid, Xumin Chen, W Echtenkamp, Axel Enders, Christian Binek, Peter A. Dowben
Peter Dowben Publications
We demonstrate boundary spin polarization at the surface of a Cr2O3 single crystal using spin-polarized low-energy electron microscopy (SPLEEM), complementing prior spin polarized photoemission, spin polarized inverse photoemission, and x-ray magnetic circular dichroism photoemission electron microscopy measurements. This work shows that placing a Cr2O3 single crystal into a single domain state will result in net Cr2O3 spin polarization at the boundary, even in the presence of a gold overlayer. There are indications that the SPLEEM contrast for the two polarization states may be different, consistent with scanning tunneling microscopy spectroscopy results …
The Spin State Of A Molecular Adsorbate Driven By The Ferroelectric Substrate Polarization†, Xin Zhang, Tatiana Palamarciuc, Jean-François Létard, Patrick Rosa, Eduardo Vega Lozada, Fernand Torres, Luis G. Rosa, Bernard Doudin, Peter A. Dowben
The Spin State Of A Molecular Adsorbate Driven By The Ferroelectric Substrate Polarization†, Xin Zhang, Tatiana Palamarciuc, Jean-François Létard, Patrick Rosa, Eduardo Vega Lozada, Fernand Torres, Luis G. Rosa, Bernard Doudin, Peter A. Dowben
Peter Dowben Publications
The spin state of [Fe(H2B(pz)2)2(bipy)] thin films is mediated by changes in the electric field at the interface of organic ferroelectric polyvinylidene fluoride with trifluoroethylene (PVDF–TrFE). Signatures of the molecular crossover transition are evident in changes in the unoccupied states and the related shift from diamagnetic to paramagnetic characteristics. This may point the way to the molecular magneto-electric effect on devices.
Increasing The Neel Temperature Of Magnetoelectric Chromia For Voltage-Controlled Spintronics, M Street, W Echtenkamp, Takashi Komesu, Shi Cao, Peter A. Dowben, Christian Binek
Increasing The Neel Temperature Of Magnetoelectric Chromia For Voltage-Controlled Spintronics, M Street, W Echtenkamp, Takashi Komesu, Shi Cao, Peter A. Dowben, Christian Binek
Peter Dowben Publications
Boron doped chromia (Cr2O3) thin films with substitutional doping levels between zero and 3% are grown using pulsed laser deposition in borane background gases. Magnetometry reveals a tunable increase in the Neel temperature of the (0001) textured Cr2BxO3-x thin films at a rate of about 10% with 1% oxygen site substitution preserving a net boundary magnetization. Spin resolved inverse photoemission measured after magnetoelectric annealing in subsequently reversed electric fields evidences voltage-controlled reversal of boundary magnetization and thus magnetoelectricity of Cr2BxO3-x. Conservation of magnetoelectricity far above …
Occupied And Unoccupied Electronic Structure Of Na Doped Mos2(0001), Takashi Komesu, Duy Le, Xin Zhang, Quan Ma, Eike F. Schwier, Yohei Kojima, Mintian Zheng, Hideaki Iwasawa, Kenya Shimada, Masaki Taniguchi, Ludwig Bartels, Talat S. Rahman, Peter A. Dowben
Occupied And Unoccupied Electronic Structure Of Na Doped Mos2(0001), Takashi Komesu, Duy Le, Xin Zhang, Quan Ma, Eike F. Schwier, Yohei Kojima, Mintian Zheng, Hideaki Iwasawa, Kenya Shimada, Masaki Taniguchi, Ludwig Bartels, Talat S. Rahman, Peter A. Dowben
Peter Dowben Publications
The influence of sodium on the band structure of MoS2(0001) and the comparison of the experimental band dispersion with density functional theory show excellent agreement for the occupied states (angle-resolved photoemission) and qualitative agreement for the unoccupied states (inverse photoemission spectroscopy). Na-adsorption leads to charge transfer to the MoS2 surface causing an effect similar to n-type doping of a semiconductor. The MoS2 occupied valence band structure shifts rigidly to greater binding with little change in the occupied state dispersion. Likewise, the unoccupied states shift downward, approaching the Fermi level, yet the amount of the shift for …
The Chromium Site In Doped Glassy Lithium Tetraborate, T D. Kelly, E Echeverria, Sumit Beniwal, V T. Adamiv, Ya V. Burak, Axel Enders, J. C. Petrosky, J W. Mcclory, Peter A. Dowben
The Chromium Site In Doped Glassy Lithium Tetraborate, T D. Kelly, E Echeverria, Sumit Beniwal, V T. Adamiv, Ya V. Burak, Axel Enders, J. C. Petrosky, J W. Mcclory, Peter A. Dowben
Peter Dowben Publications
Using extended X-ray absorption fine structure (EXAFS) spectroscopy, we find that Cr substitutes primarily in the Liþ site as a dopant in lithium tetraborate Li2B4O7 glasses, in this case 98.4Li2B4O7e1.6Cr2O3 or nominally Li1.98Cr0.025B4O7. This strong preference for a single site is nonetheless accompanied by site distortions and some site disorder, helping explain the optical properties of chromium doped Li2B4O7 glasses. The resulting O coordination shell has a contraction of the Cr-O …
Sublattice-Induced Symmetry Breaking And Bandgap Formation In Graphene, Ralph A. Skomski, Peter A. Dowben, M Sky Driver, Jeffery A. Kelber
Sublattice-Induced Symmetry Breaking And Bandgap Formation In Graphene, Ralph A. Skomski, Peter A. Dowben, M Sky Driver, Jeffery A. Kelber
Peter Dowben Publications
A reduction of symmetry from C6v to C3v leads to the opening of a band gap in the otherwise gapless semiconductor graphene. Simple models provide a fairly complete picture of this mechanism for opening a band gap and in fact can be discussed in terms of the tight-binding approximation, accurately resolving the wave-vector space to a very high accuracy. This picture is consistent with experiments that yield a band gap due to A and B graphene-site symmetry breaking due to substrate interactions.
The Unoccupied Electronic Structure Characterization Of Hydrothermally Grown Tho2 Single Crystals, T D. Kelly, J C. Petrosky, D Turner, J W. Mcclory, J M. Mann, J W. Kolis, Xin Zhang, Peter A. Dowben
The Unoccupied Electronic Structure Characterization Of Hydrothermally Grown Tho2 Single Crystals, T D. Kelly, J C. Petrosky, D Turner, J W. Mcclory, J M. Mann, J W. Kolis, Xin Zhang, Peter A. Dowben
Peter Dowben Publications
Single crystals of thorium dioxide ThO2, grown by the hydrothermal growth technique, have been investigated by ultraviolet photoemission spectroscopy (UPS), inverse photoemission spectroscopy (IPES), and L3, M3, M4, and M5 X-ray absorption near edge spectroscopy (XANES). The experimental band gap for large single crystals has been determined to be 6 eV to 7 eV, from UPS and IPES, in line with expectations. The combined UPS and IPES, place the Fermi level near the conduction band minimum, making these crystals n-type, with extensive band tailing, suggesting an optical gap in the region …