486 research outputs found
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
Pseudogap of metallic layered nickelate R2-xSrxNiO4 (R=Nd, Eu) crystals measured using angle-resolved photoemission spectroscopy
We have investigated charge dynamics and electronic structures for single
crystals of metallic layered nickelates, R2-xSrxNiO4 (R=Nd, Eu), isostructural
to La2-xSrxCuO4. Angle-resolved photoemission spectroscopy on the
barely-metallic Eu0.9Sr1.1NiO4 (R=Eu, x=1.1) has revealed a large hole surface
of x2-y2 character with a high-energy pseudogap of the same symmetry and
comparable magnitude with those of underdoped (x<0.1) cuprates, although the
antiferromagnetic interactions are one order of magnitude smaller. This finding
strongly indicates that the momentum-dependent pseudogap feature in the layered
nickelate arises from the real-space charge correlation.Comment: 4 pages, 4 figures. Accepted in Physical Review Letter
Contrasting Pressure Effects in Sr2VFeAsO3 and Sr2ScFePO3
We report the resistivity measurements under pressure of two Fe-based
superconductors with a thick perovskite oxide layer, Sr2VFeAsO3 and Sr2ScFePO3.
The superconducting transition temperature Tc of Sr2VFeAsO3 markedly increases
with increasing pressure. Its onset value, which was Tc{onset}=36.4 K at
ambient pressure, increases to Tc{onset}=46.0 K at ~4 GPa, ensuring the
potential of the "21113" system as a high-Tc material. However, the
superconductivity of Sr2ScFePO3 is strongly suppressed under pressure. The
Tc{onset} of ~16 K decreases to ~5 K at ~4 GPa, and the zero-resistance state
is almost lost. We discuss the factor that induces this contrasting pressure
effect.Comment: 5 pages, 4 figures, to be published in J. Phys. Soc. Jpn. No.12
(2009
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