407 research outputs found
Lattice-form dependent orbital shape and charge disproportionation in charge- and orbital-ordered manganites
The orbital shapes and charge disproportionations at nominal Mn and
Mn sites for the charge- and orbital-ordered phases have been studied on
half-doped manganites Pr(SrCa)MnO and
EuCaMnO with double-layer and single-layer Mn-O networks,
respectively, by means of x-ray structural analyses, in comparison with
PrCaMnO with the pseudo cubic network. In a single-layer
EuCaMnO system, the ()/()-type orbital
shape is observed, while the ()/()-type orbital shape in a
pseudo cubic PrCaMnO system. In a double-layer
Pr(SrCa)MnO system, the orbital shape is found to
undergo a large change upon thermally induced rotation of orbital stripe.
Furthermore, clear charge disproportionation is observed for the pseudo cubic
and double-layer systems, while not in the single-layer system. These results
indicate that the orbital shape and charge disproportionation are sensitive to
the dimension of Mn-O network.Comment: 12 page, 5 figures, 11 table
Endplate potential oscillation of jaw closing muscles in natural chewing.
Surface electromyograms (EMGs) in natural gum chewing were recorded in a monopolar manner from paired anterior temporalis and masseter muscles of four subjects. Electrodes were placed on the temple of the former muscle, and on the inferior portion of the latter muscle. The endplate potential (EPP) component was extracted from raw EMGs of the muscles using a digital filter: the frequency of the high-cut digital filter for eliminating action potentials was set to 12.5 Hz or 45 Hz. The EPP component of the EMG burst of each stroke in the natural chewing showed two phases, early negative slow wave and following oscillation, which was same as observed in the clenching task. From FFT analysis, the frequencies of the ipsilateral EPP oscillations were around 30 Hz for both the temporalis and masseter muscles, which was also the same for the clenching task. It is concluded that the contraction of the jaw closing muscles is regulated in an oscillating manner of the EPP even in natural chewing behaviors. This oscillation phenomenon of the EPP gives a useful hint about the mechanism of muscular movements including chewing
Epitaxial-strain effect on charge/orbital order in Pr0.5Ca0.5MnO3 films
Effect of growth orientation on charge- and orbital-ordering (CO-OO)
phenomena has been studied for Pr0.5Ca0.5MnO3 epitaxial thin films fabricated
on (LaAlO3)0.3-(SrAl0.5Ta0.5O3)0.7 (LSAT) substrates by means of resistivity,
synchrotron x-ray diffraction, and polarized optical microscopy measurements.
CO-OO transition is observed around 220 K for a film grown on an LSAT (011)
substrate ((011)-film), similarly to a bulk sample, while a film grown on a
(001) plane of LSAT ((001)-film) shows much higher transition temperature
around 300 K. The domain size of OO is approximately 3 times as large in the
(011)-film as in the (001)-film. These results demonstrate that various
properties of CO-OO phenomena can be controlled with the growth orientation via
the epitaxial strain from the substrate.Comment: 4 pages, 4 figure
Bandwidth-disorder phase diagram of half doped layered manganites
Phase diagrams in the plane of (the average ionic radius, related to
one-electron bandwidth ) and (the ionic radius variance,
measuring the quenched disorder), or ``bandwidth-disorder phase diagrams'',
have been established for perovskite manganites, with three-dimensional (3)
Mn-O network. Here we establish the intrinsic bandwidth-disorder phase diagram
of half-doped layered manganites with the two-dimensional (2) Mn-O network,
examining in detail the ``mother state'' of the colossal magnetoresistance
(CMR) phenomenon in crystals without ferromagnetic instability. The
consequences of the reduced dimensionality, from 3 to 2, on the
order-disorder phenomena in the charge-orbital sectors are also highlighted.Comment: REVTeX 4 style; 5 pages, 4 figure
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