3,675 research outputs found
MnSi nanoparticles embedded in Si: Superparamagnetism with a collective behavior
The doping of Mn in Si is attracting research attentions due to the
possibility to fabricate Si-based diluted magnetic semiconductors. However, the
low solubility of Mn in Si favors the precipitation of Mn ions even at
non-equilibrium growth conditions. MnSi nanoparticles are the common
precipitates, which show exotic magnetic properties in comparison with the
MnSi bulk phase. In this paper we present the static and dynamic
magnetic properties of MnSi nanoparticles. Using the Preisach model, we
derive the magnetic parameters, such as the magnetization of individual
particles, the distribution of coercive fields and the inter-particle
interaction field. Time-dependent magnetization measurements reveal a
spin-glass behavior of the system.Comment: 11 pages, 6 figures, submitted to PR
Absence of ferromagnetism in V-implanted ZnO single crystals
The structural and magnetic properties of V doped ZnO are presented. V ions
were introduced into hydrothermal ZnO single crystals by ion implantation with
fluences of 1.2*10^16 to 6*10^16 cm^-2. Post-implantation annealing was
performed in high vacuum from 823 K to 1023 K. The ZnO host material still
partly remains in a crystalline state after irradiation, and is partly
recovered by annealing. The V ions show a thermal mobility as revealed by depth
profile Auger electron spectroscopy. Synchrotron radiation x-ray diffraction
revealed no secondary phase formation which indicates the substitution of V
onto Zn site. However in all samples no pronounced ferromagnetism was observed
down to 5 K by a superconducting quantum interference device magnetometer.Comment: 13 pages, 4 figs, MMM conference 2007, accepted by J. Appl. Phy
Origin of magnetic moments in defective TiO2 single crystals
In this paper we show that ferromagnetism can be induced in pure TiO2 single
crystals by oxygen ion irradiation. By combining x-ray diffraction,
Raman-scattering, and electron spin resonance spectroscopy, a defect complex,
\emph{i.e.} Ti ions on the substitutional sites accompanied by oxygen
vacancies, has been identified in irradiated TiO2. This kind of defect complex
results in a local (TiO) stretching Raman mode. We elucidate that
Ti ions with one unpaired 3d electron provide the local magnetic
moments.Comment: 4 pages, 4 figures, to be published at Phys. Rev.
Interface steps in field effect devices
The charge doped into a semiconductor in a field effect transistor (FET) is
generally confined to the interface of the semiconductor. A planar step at the
interface causes a potential drop due to the strong electric field of the FET,
which in turn is screened by the doped carriers. We analyze the dipolar
electronic structure of a single step in the Thomas-Fermi approximation and
find that the transmission coefficient through the step is exponentially
suppressed by the electric field and the induced carrier density as well as by
the step height. In addition, the field enhancement at the step edge can
facilitate the electric breakthrough of the insulating layer. We suggest that
these two effects may lead to severe problems when engineering FET devices with
very high doping. On the other hand steps can give rise to interesting physics
in superconducting FETs by forming weak links and potentially creating atomic
size Josephson junctions.Comment: 6 pages, 4 figures, submitted to J. Appl. Phy
The use of xenografts to prevent inferior border defects following bilateral sagittal split osteotomies:three-dimensional skeletal analysis using cone beam computed tomography
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Aplicação do bagaço de cana como biomassa energética e do sulfato de amônia como fonte de nitrogênio para sÃntese de celulases por Lentinula edodes.
Editores técnicos: MarcÃlio José Thomazini, Elenice Fritzsons, PatrÃcia Raquel Silva, Guilherme Schnell e Schuhli, Denise Jeton Cardoso, Luziane Franciscon. EVINCI. Resumos
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