262 research outputs found
The Impact of Security and Privacy Concerns on Home Internet Use by Parents and Children
Internet users’ choices about their extent and types of usage and the types of precautions they take for their online security and privacy is an increasingly important research topic. As business and personal Internet usage grows so do concerns about misuse and abuse leading to financial loss or breaches of privacy. For the younger user, the risk of sexual exploitation from misuse is a particular concern. Effective mitigation of these risks is critical to the full achievement of the benefits the Internet can offer in e-commerce, e-learning, business and social communication. The interrelations between comfort with sensitive Internet use, security measures taken, and the types of Internet usage among home Internet users has not been extensively examined. We plan to empirically examine these interactions and to then extend our analysis to examine the impact of parental attitudes, usage, and controls on Internet usage
Resistive relaxation in field-induced insulator-metal transition of a (LaPr)SrMnO bilayer manganite single crystal
We have investigated the resistive relaxation of a
(LaPr)SrMnO single crystal, in
order to examine the slow dynamics of the field-induced insulator to metal
transition of bilayered manganites. The temporal profiles observed in remanent
resistance follow a stretched exponential function accompanied by a slow
relaxation similar to that obtained in magnetization and magnetostriction data.
We demonstrate that the remanent relaxation in magnetotransport has a close
relationship with magnetic relaxation that can be understood in the framework
of an effective medium approximation by assuming that the first order parameter
is proportional to the second order one.Comment: 6 pages,5 figure
Stretched exponential behavior in remanent lattice striction of a (La,Pr)SrMnO bilayer manganite single crystal
We have investigated the time dependence of remanent magnetostriction in a
(La,Pr)SrMnO single crystal, in order to examine
the slow dynamics of lattice distortion in bilayered manganites. A competition
between double exchange and Jahn-Teller type orbital-lattice interactions
results in the observed lattice profile following a stretched exponential
function. This finding suggests that spatial growth of the local lattice
distortions coupled with e-electron orbital strongly correlates with the
appearance of the field-induced CMR effect.Comment: 3 figure
Effect of suppression of local distortion on magnetic, electrical and thermal transport properties of Cr substituted bi-layer manganite LaSrMnO
We have investigated magnetic, electrical and thermal transport properties
(Seebeck effect and thermal conductivity) of
LaSrMnCrO polycrystalline samples (=0.1, 0.2, 0.4
and 0.6). The Cr substitution for Mn sites causes a removal of
orbital of -electron resulting in a volume shrinkage of
lattice. Magnetic measurements reveal the appearance of a glassy behavior for
Cr-doped samples, accompanied by both a collapse of the A-type
antiferromagnetic structure and the growth of ferromagnetic clusters. Cr-doping
effect on electrical transport strongly enhances an insulating behavior over a
wide range of temperature, while it suppresses a local minimum of
thermoelectric power at lower temperatures. The phonon thermal conduction
gradually rises with increasing Cr content, which is contradictory to a typical
impurity effect on thermal conductivity. We attribute this to a suppression of
local lattice distortion through the introduction of Jahn-Teller inactive ions
of Cr.Comment: 8 pages, 9figure
Colossal electroresistance and colossal magnetoresistive step in paramagnetic insulating phase of single crystalline bilayered manganite(LaPr)SrMnO
We report a significant decrease in the low-temperature resistance induced by
the application of an electric current on the -plane in the paramagnetic
insulating (PMI) state of
(LaPr)SrMnO. A colossal
electroresistance effect attaining -95% is observed at lower temperatures. A
colossal magnetoresistive step appears near 5T at low temperatures below 10K,
accompanied by an ultrasharp width of the insulator-metal transition. Injection
of higher currents to the crystal causes a disappearance of the steplike
transition. These findings have a close relationship with the presence of the
short-range charge-ordered clusters pinned within the PMI matrix of the crystal
studied.Comment: 4 pages 3 figure
Anomalous pressure effect on the remanent lattice striction of a (La,Pr)SrMnO bilayered manganite single crystal
We have studied the pressure effect on magnetostriction, both in the
-plane and along the c-axis, of a (La,Pr)SrMnO
bilayered manganite single crystal over the temperature region where the
field-induced ferromagnetic metal (FMM) transition takes place. For comparison,
we have also examined the pressure dependence of magnetization curves at the
corresponding temperatures. The applied pressure reduces the critical field of
the FMM transition and it enhances the remanent magnetostriction. An anomalous
pressure effect on the remanent lattice relaxation is observed and is similar
to the pressure effect on the remanent magnetization along the c-axis. These
findings are understood from the view point that the double-exchange
interaction driven FMM state is strengthened by application of pressure.Comment: 7 pages,7 figure
Steplike Lattice Deformation of Single Crystalline (LaPr)SrMnO Bilayered Manganite
We report a steplike lattice transformation of single crystalline
(LaPr)SrMnObilayered manganite
accompanied by both magnetization and magnetoresistive jumps, and examine the
ultrasharp nature of the field-induced first-order transition from a
paramagnetic insulator to a ferromagnetic metal phase accompanied by a huge
decrease in resistance. Our findings support that the abrupt magnetostriction
is closely related to an orbital frustration existing in the inhomogeneous
paramagnetic insulating phase rather than a martensitic scenario between
competing two phases.Comment: 5 pages,4figures, v4: figures are changed, in press in Phys.Rev.Let
Ferromagnetism at 300 K in spin-coated anatasea and rutile Ti0.95Fe0.05O2 films
Thin films of Ti1-xFexO2 (x=0 and 0.05) have been prepared on sapphire
substrates by spin-on technique starting from metal organic precursors. When
heat treated in air at 550 and 700 degrees C respectively, these films present
pure anatase and rutile structures as shown both by X-ray diffraction and Raman
spectroscopy. Optical absorption indicate a high degree of transparency in the
visible region. Such films show a very small magnetic moment at 300 K. However,
when the anatase and the rutile films are annealed in a vacuum of 1x10-5 Torr
at 500 degrees C and 600 degrees C respectively, the magnetic moment, at 300 K,
is strongly enhanced reaching 0.46 B/Fe for the anatase sample and 0.48
B/Fe for the rutile one. The ferromagnetic Curie temperature of these
samples is above 350 K.Comment: 13 october 200
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