862 research outputs found
Evolution of ferromagnetic circular dichroism coincident with magnetization and anomalous Hall effect in Co-doped rutile TiO2
Magnetic circular dichroism (MCD) of rutile Ti1-xCoxO2-d is systematically
examined with various x and d to reveal a phase diagram for the appearance of
ferromagnetism at higher carrier concentration and Co content. The phase
diagram exactly matches with that determined from anomalous Hall effect (AHE).
The magnetic field dependence of MCD also shows good coincidence with those of
the magnetization and AHE. The coincidence of these independent measurements
strongly suggests single and intrinsic ferromagnetic origin.Comment: 9 pages, 4 figure
Role of charge carriers for ferromagnetism in cobalt-doped rutile TiO2
Electric and magnetic properties of a high temperature ferromagnetic oxide
semiconductor, cobalt-doped rutile TiO2, are summarized. The cobalt-doped
rutile TiO2 epitaxial thin films with different electron densities and cobalt
contents were grown on r-sapphire substrates with laser molecular beam epitaxy.
Results of magnetization, magnetic circular dichroism, and anomalous Hall
effect measurements were examined for samples with systematically varied
electron densities and cobalt contents. The samples with high electron
densities and cobalt contents show the high temperature ferromagnetism,
suggesting that charge carriers induce the ferromagnetism.Comment: 14 pages, 12 figure
Bulk and Surface Magnetization of Co atoms in Rutile Ti_[1-x]Co_xO_[2-delta] Thin Films Revealed by X-Ray Magnetic Circular Dichroism
We have studied magnetism in Ti_[1-x]Co_xO_[2-\delta] thin films with various
x and \delta by soft x-ray magnetic circular dichroism (XMCD) measurements at
the Co L_[2,3] absorption edges. The estimated ferromagnetic moment by XMCD was
0.15-0.24 \mu\beta/Co in the surface, while in the bulk it was 0.82-2.25
\mu\beta/Co, which is in the same range as the saturation magnetization of
1.0-1.5 \mu\beta/Co. Theseresults suggest that the intrinsic origin of the
erromagnetism. The smaller moment of Co atom at surface is an indication of a
magnetically dead layer of a few nm thick at the surface of the thin films.Comment: This Paper is accepted in J. of Phys: Conds. Matte
Magnetic oxide semiconductors
Magnetic oxide semiconductors, oxide semiconductors doped with transition
metal elements, are one of the candidates for a high Curie temperature
ferromagnetic semiconductor that is important to realize semiconductor
spintronics at room temperature. We review in this paper recent progress of
researches on various magnetic oxide semiconductors. The magnetization,
magneto-optical effect, and magneto-transport such as anomalous Hall effect are
examined from viewpoint of feasibility to evaluate the ferromagnetism. The
ferromagnetism of Co-doped TiO2 and transition metal-doped ZnO is discussed.Comment: 26 pages, 5 tables, 6 figure
Human anisakiasis transmitted by marine food products.
Seafood-transmitted parasitic diseases represent an emerging area of interest to the U.S. Food and Drug Administration. Human infections with marine parasites are generally the result of ingesting uncooked seafood products. Over 50 species of helminthic parasites are known to infect humans worldwide. Recently, the number of infections with one of these helminths, the juvenile stage of the marine nematode, Anisakis simplex, has increased in the United States. Raw fish dishes such as lomi lomi salmon and sashimi are known to transmit the parasite to unsuspecting citizens and the most frequently implicated fish in the transmission of this zoonotic disease is the Pacific salmon (Oncorhynchus spp.). The risk of infection from fishes caught in Hawaiian waters is slight; however, a juvenile Anisakis simplex infected one patient from either locally caught aku or ahi. We report 4 new cases, which brings the total number of known cases in Hawaii to 7. Five of the 7 cases were diagnosed and treated by means of an endoscope and biopsy forceps. Serological profiles are presented in several of these cases. One case represents the first known instance of reinfection; the initial infection occurred 2 years prior. The second infection gave an opportunity to compare the human response to a challenge infection and to investigate the validity of the "double hit" theory. Increased awareness by physicians to the clinical features of this disease is warranted. The zoonotic disease, anisakiasis, should be considered in patients presenting with intense abdominal pain, if these patients admit they have recently eaten raw or undercooked seafoods.AI 19968/AI/NIAID NIH HHS/United State
Temperature dependent optical properties of -GaO thin films
We determined the complex dielectric functions of -GaO
using optical transmittance and reflectance spectroscopies at temperatures from
10 K to room temperature. The measured dielectric-function spectra reveal
distinct structures at a bandgap energy. We fitted a model dielectric function
based on the electronic energy-band structure to these experimental data. We
analyzed the temperature dependence of the band-gap with a model based on
phonon dispersion effects. One could explain it in terms of phonon-related
parameters such as the optical phonon temperature. We compare phonon-related
properties of -GaO with those of a large variety of
element and binary semiconductors.Comment: 10 pages, 6 png figures, using arxiv.st
Photoreflectance spectroscopy of BiOCl epitaxial thin films
We have observed a new optical transition in the photoreflectance spectra of
indirect-gap BiOCl thin films, which were grown on SrTiO substrates. The
position of this transition is close in energy to its bulk critical point
energy. Moreover, these are significantly lower than a higher-lying direct-type
critical point from an energetic point of view. The spectral line shape
analysis for our observed signal suggests the presence of an excitonic effect
of this compound. We determined its dependence of the optical anomaly on
temperature ranging from 80 K to room temperature. We adopted the Varshni model
for this analysis. At last, we compared phononic properties of BiOCl with those
of an element and binary semiconductors.Comment: 9 pages, 4 figures, submitted to Jpn. J. Appl. Phy
Ultrafast optical control of magnetization in EuO thin films
All-optical pump-probe detection of magnetization precession has been
performed for ferromagnetic EuO thin films at 10 K. We demonstrate that the
circularly-polarized light can be used to control the magnetization precession
on an ultrafast time scale. This takes place within the 100 fs duration of a
single laser pulse, through combined contribution from two nonthermal
photomagnetic effects, i.e., enhancement of the magnetization and an inverse
Faraday effect. From the magnetic field dependences of the frequency and the
Gilbert damping parameter, the intrinsic Gilbert damping coefficient is
evaluated to be {\alpha} \approx 3\times10^-3.Comment: 5 pages, 3 figures, accepted for publication in Phys. Rev.
Signature of Carrier-Induced Ferromagnetism in Ti_{1-x}Co_{x}O_{2-delta}: Exchange Interaction Between High-Spin Co 2+ and the Ti 3d Conduction Band
X-ray photoemission spectroscopy measurements were performed on thin-film
samples of rutile Ti_{1-x}Co_{x}O_{2-delta} to reveal the electronic structure.
The Co 2p core level spectra indicate that the Co ions take the high-spin Co 2+
configuration, consistent with substitution on the Ti site. The high spin state
and the shift due to the exchange splitting of the conduction band suggest
strong hybridization between carriers in the Ti 3d t2g band and the t2g states
of the high-spin Co 2+. These observations support the argument that room
temperature ferromagnetism in Ti_{1-x}Co_{x}O_{2-delta} is intrinsic.Comment: 4 pages, 5 figures. Accepted for publication in Physical Review
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