8,644 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
Fast Compact Laser Shutter Using a Direct Current Motor and 3D Printing
We present a mechanical laser shutter design that utilizes a DC electric
motor to rotate a blade which blocks and unblocks a light beam. The blade and
the main body of the shutter are modeled with computer aided design (CAD) and
are produced by 3D printing. Rubber flaps are used to limit the blade's range
of motion, reducing vibrations and preventing undesirable blade oscillations.
At its nominal operating voltage, the shutter achieves a switching speed of
(1.22 0.02) m/s with 1 ms activation delay and 10 s jitter in its
timing performance. The shutter design is simple, easy to replicate, and highly
reliable, showing no failure or degradation in performance over more than
cycles.Comment: 4 pages, 6 figures; supplementary materials for shutter replication
added under "Ancillary files
Spectrum of Background X-rays from Moduli Dark Matter
We examine the -ray spectrum from the decay of the dark-matter moduli with
mass keV, in particular, paying attention to the line
spectrum from the moduli trapped in the halo of our galaxy. It is found that
with the energy resolution of the current experiments (%) the line
intensity is about twice stronger than that of the continuum spectrum from the
moduli that spread in the whole universe. Therefore, in the future experiments
with higher energy resolutions it may be possible to detect such line photons.
We also investigate the -ray spectrum emitted from the decay of the
multi-GeV moduli. It is shown that the emitted photons may form MeV-bump in the
-ray spectrum. We also find that if the modulus mass is of the order of
10 GeV, the emitted photons at the peak of the continuum spectrum loses their
energy by the scattering and the shape of the spectrum is significantly
changed, which makes the constraint weaker than that obtained in the previous
works.Comment: 14 pages (RevTeX file) including four postscript figures, reviced
version to be published in Physical Review
^{115}In-NQR evidence for unconventional superconductivity in CeIn_3 under pressure
We report evidence for unconventional superconductivity in CeIn_3 at a
pressure P = 2.65 GPa above critical pressure (P_c ~ 2.5 GPa) revealed by the
measurements of nuclear-spin-lattice-relaxation time (T_1) and
ac-susceptibility (ac-chi). Both the measurements of T_1 and ac-chi have
pointed to a superconducting transition at T_c = 95 mK, which is much lower
than an onset temperature T_{onset} = 0.15 K at zero resistance. The
temperature dependence of 1/T_1 shows no coherence peak just below T_c,
indicative of an unconventional nature for the superconductivity induced in
CeIn_3.Comment: 4 pages, 4 figures, to be published in Phys.Rev.
Field-Effect Transistor on SrTiO3 with sputtered Al2O3 Gate Insulator
A field-effect transistor that employs a perovskite-type SrTiO3 single
crystal as the semiconducting channel is revealed to function as n-type
accumulation-mode device with characteristics similar to that of organic FET's.
The device was fabricated at room temperature by sputter-deposition of
amorphous Al2O3 films as a gate insulator on the SrTiO3 substrate. The
field-effect(FE) mobility is 0.1cm2/Vs and on-off ratio exceeds 100 at room
temperature. The temperature dependence of the FE mobility down to 2K shows a
thermal-activation-type behavior with an activation energy of 0.6eV
Hole Transport in p-Type ZnO
A two-band model involving the A- and B-valence bands was adopted to analyze
the temperature dependent Hall effect measured on N-doped \textit{p}-type ZnO.
The hole transport characteristics (mobilities, and effective Hall factor) are
calculated using the ``relaxation time approximation'' as a function of
temperature. It is shown that the lattice scattering by the acoustic
deformation potential is dominant. In the calculation of the scattering rate
for ionized impurity mechanism, the activation energy of 100 or 170 meV is used
at different compensation ratios between donor and acceptor concentrations. The
theoretical Hall mobility at acceptor concentration of
cm is about 70 cmVs with the activation energy of 100 meV
and the compensation ratio of 0.8 at 300 K. We also found that the compensation
ratios conspicuously affected the Hall mobilities.Comment: 5page, 5 figures, accepted for publication in Jpn. J. Appl. Phy
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