159 research outputs found
A case report: isolation of alysiella filiformis from pig"s lungs
Alysiella filiformis is considered a common resident in the oral cavities of many animals. All reports of Alysiella indicate that it is restricted to the oral cavity of warm-blooded vertebrates, where it apparently is nonpathogenic. However, increased losses of young pigs occured in one farm in Serbia. Spumous content in bronchia and partly clotted blood in blood vesels o f the lungs were present. Characteristic signs of oedema disease were present and E. coli serogroup 0139 was isolated. Furthermore, Alysiella filiformis was the single agent isolated from the lungs of diseased pigs. This is the first isolation of Alysiella filiformis from pig lungs
Robust Magnetic Polarons in Type-II (Zn,Mn)Te Quantum Dots
We present evidence of magnetic ordering in type-II (Zn, Mn) Te quantum dots.
This ordering is attributed to the formation of bound magnetic polarons caused
by the exchange interaction between the strongly localized holes and Mn within
the dots. In our photoluminescence studies, the magnetic polarons are detected
at temperatures up to ~ 200 K, with a binding energy of ~ 40 meV. In addition,
these dots display an unusually small Zeeman shift with applied field (2 meV at
10 T). This behavior is explained by a small and weakly temperature-dependent
magnetic susceptibility due to anti-ferromagnetic coupling of the Mn spins
Low Temperature Behavior of the Vortex Lattice in Unconventional Superconductors
We study the effect of the superconducting gap nodes on the vortex lattice
properties of high temperature superconductors at very low temperatures. The
nonlinear, nonlocal and nonanalytic nature of this effect is shown to have
measurable consequences for the vortex lattice geometry and the effective
penetration depth in the mixed state as measured by muon-spin-rotation
experiments.Comment: 3 figures and extensive discussion added, Version to appear in
September 1 issue of PR
Ground state properties of ferromagnetic metal/conjugated polymer interfaces
We theoretically investigate the ground state properties of ferromagnetic
metal/conjugated polymer interfaces. The work is partially motivated by recent
experiments in which injection of spin polarized electrons from ferromagnetic
contacts into thin films of conjugated polymers was reported. We use a
one-dimensional nondegenerate Su-Schrieffer-Heeger (SSH) Hamiltonian to
describe the conjugated polymer and one-dimensional tight-binding models to
describe the ferromagnetic metal. We consider both a model for a conventional
ferromagnetic metal, in which there are no explicit structural degrees of
freedom, and a model for a half-metallic ferromagnetic colossal
magnetoresistance (CMR) oxide which has explicit structural degrees of freedom.
The Fermi energy of the magnetic metallic contact is adjusted to control the
degree of electron transfer into the polymer. We investigate electron charge
and spin transfer from the ferromagnetic metal to the organic polymer, and
structural relaxation near the interface. Bipolarons are the lowest energy
charge state in the bulk polymer for the nondegenerate SSH model Hamiltonian.
As a result electrons (or holes) transferred into the bulk of the polymer form
spinless bipolarons. However, there can be spin density in the polymer
localized near the interface.Comment: 7 figure
Nano granular metallic Fe - oxygen deficient TiO composite films: A room temperature, highly carrier polarized magnetic semiconductor
Nano granular metallic iron (Fe) and titanium dioxide (TiO) were
co-deposited on (100) lanthanum aluminate (LaAlO) substrates in a low
oxygen chamber pressure using a pulsed laser ablation deposition (PLD)
technique. The co-deposition of Fe and TiO resulted in 10 nm
metallic Fe spherical grains suspended within a TiO matrix. The
films show ferromagnetic behavior with a saturation magnetization of 3100 Gauss
at room temperature. Our estimate of the saturation magnetization based on the
size and distribution of the Fe spheres agreed well with the measured value.
The film composite structure was characterized as p-type magnetic semiconductor
at 300 K with a carrier density of the order of . The
hole carriers were excited at the interface between the nano granular Fe and
TiO matrix similar to holes excited in the metal/n-type
semiconductor interface commonly observed in Metal-Oxide-Semiconductor (MOS)
devices. From the large anomalous Hall effect directly observed in these films
it follows that the holes at the interface were strongly spin polarized.
Structure and magneto transport properties suggested that these PLD films have
potential nano spintronics applications.Comment: 6 pages in Latex including 8 figure
Drift-Diffusion Approach to Spin-Polarized Transport
We develop a drift-diffusion equation that describes electron spin
polarization density in two-dimensional electron systems. In our approach,
superpositions of spin-up and spin-down states are taken into account, what
distinguishes our model from the traditional two-component drift-diffusion
approximation. The Dresselhaus and Rashba spin-orbit coupling mechanisms are
incorporated into consideration, as well as an applied electric field. The
derived equation is applied to the modelling of relaxation of homogeneous spin
polarization. Our results are consistent with previous studies
Andreev Reflection and Spin Injection into and wave Superconductors
We study the effect of spin injection into and wave superconductors,
with an emphasis on the interplay between boundary and bulk spin transport
properties. The quantities of interest include the amount of non-equilibrium
magnetization (), as well as the induced spin-dependent current () and
boundary voltage (). In general, the Andreev reflection makes each of the
three quantities depend on a different combination of the boundary and bulk
contributions. The situation simplifies either for half-metallic ferromagnets
or in the strong barrier limit, where both and depend solely on the
bulk spin transport/relaxation properties. The implications of our results for
the on-going spin injection experiments in high cuprates are discussed.Comment: 4 pages, REVTEX, 1 figure included; typos correcte
Transport properties of ferromagnet/d-wave superconductor/ferromagnet double junctions
We investigate transport properties of a trilayer made of a d-wave
superconductor connected to two ferromagnetic electrodes. Using Keldysh
formalism we show that crossed Andreev reflection and elastic cotunneling exist
also with d-wave superconductors. Their properties are controlled by the
existence of zero energy states due to the anisotropy of the d-wave pair
potential.Comment: 16 pages, 4 figures, revised versio
Experimental observation of the optical spin transfer torque
The spin transfer torque is a phenomenon in which angular momentum of a spin
polarized electrical current entering a ferromagnet is transferred to the
magnetization. The effect has opened a new research field of electrically
driven magnetization dynamics in magnetic nanostructures and plays an important
role in the development of a new generation of memory devices and tunable
oscillators. Optical excitations of magnetic systems by laser pulses have been
a separate research field whose aim is to explore magnetization dynamics at
short time scales and enable ultrafast spintronic devices. We report the
experimental observation of the optical spin transfer torque, predicted
theoretically several years ago building the bridge between these two fields of
spintronics research. In a pump-and-probe optical experiment we measure
coherent spin precession in a (Ga,Mn)As ferromagnetic semiconductor excited by
circularly polarized laser pulses. During the pump pulse, the spin angular
momentum of photo-carriers generated by the absorbed light is transferred to
the collective magnetization of the ferromagnet. We interpret the observed
optical spin transfer torque and the magnetization precession it triggers on a
quantitative microscopic level. Bringing the spin transfer physics into optics
introduces a fundamentally distinct mechanism from the previously reported
thermal and non-thermal laser excitations of magnets. Bringing optics into the
field of spin transfer torques decreases by several orders of magnitude the
timescales at which these phenomena are explored and utilized.Comment: 11 pages, 4 figure
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