1,220 research outputs found
Coastal subsidence in Oregon, USA, during the Giant Cascadia earthquake of AD 1700
Quantitative estimates of land-level change during the giant AD 1700 Cascadia earthquake along the Oregon coast are inferred from relative sea-level changes reconstructed from fossil foraminiferal assemblages preserved within the stratigraphic record. A transfer function, based upon a regional training set of modern sediment samples from Oregon estuaries, is calibrated to fossil assemblages in sequences of samples across buried peat-mud and peat-sand contacts marking the AD 1700 earthquake. Reconstructions of sample elevations with sample-specific errors estimate the amount of coastal subsidence during the earthquake at six sites along 400 km of coast. The elevation estimates are supported by lithological, carbon isotope, and faunal tidal zonation data. Coseismic subsidence at Nehalem River, Nestucca River, Salmon River, Alsea Bay, Siuslaw River and South Slough varies between 0.18 m and 0.85 m with errors between 0.18 m and 0.32 m. These subsidence estimates are more precise, consistent, and generally lower than previous semi-quantitative estimates. Following earlier comparisons of semi-quantitative subsidence estimates with elastic dislocation models of megathrust rupture during great earthquakes, our lower estimates for central and northern Oregon are consistent with modeled rates of strain accumulation and amounts of slip on the subduction megathrust, and thus, with a magnitude of 9 for the AD 1700 earthquake
Anisotropic magnetic field responses of ferroelectric polarization in a trigonal multiferroic CuFe1-xAlxO2 (x=0.015)
We have investigated magnetic field dependences of a ferroelectric
incommensurate-helimagnetic order in a trigonal magneto-electric (ME)
multiferroic CuFe1-xAlxO2 with x=0.015, which exhibits the ferroelectric phase
as a ground state, by means of neutron diffraction, magnetization and
dielectric polarization measurements under magnetic fields applied along
various directions. From the present results, we have established the H-T
magnetic phase diagrams for the three principal directions of magnetic fields;
(i) parallel to the c axis, (ii) parallel to the helical axis, and (iii)
perpendicular to the c and the helical axes. While the previous dielectric
polarization (P) measurements on CuFe1-xGaxO2 with x=0.035 have demonstrated
that the magnetic field dependence of the `magnetic domain structure' results
in distinct magnetic field responses of P [S. Seki et al., Phys. Rev. Lett.,
103 237601 (2009)], the present study have revealed that the anisotropic
magnetic field dependence of the ferroelectric helimagnetic order `in each
magnetic domain' can be also a source of a variety of magnetic field responses
of P in CuFe1-xAxO2 systems (A=Al, Ga).Comment: 11 pages, 9 figures, accepted for publication in Phys. Rev.
Role of Oxygen Electrons in the Metal-Insulator Transition in the Magnetoresistive Oxide LaSrMnO Probed by Compton Scattering
We have studied the [100]-[110] anisotropy of the Compton profile in the
bilayer manganite. Quantitative agreement is found between theory and
experiment with respect to the anisotropy in the two metallic phases (i.e. the
low temperature ferromagnetic and the colossal magnetoresistant phase under a
magnetic field of 7 T). Robust signatures of the metal-insulator transition are
identified in the momentum density for the paramagnetic phase above the Curie
temperature. We interpret our results as providing direct evidence for the
transition from the metallic-like to the admixed ionic-covalent bonding
accompanying the magnetic transition. The number of electrons involved in this
phase transition is estimated from the area enclosed by the Compton profile
anisotropy differences. Our study demonstrates the sensitivity of the Compton
scattering technique for identifying the number and type of electrons involved
in the metal-insulator transition.Comment: 4 pages, 4 figures, accepted for publication in Physical Review
Letter
High resolution Compton scattering as a Probe of the Fermi surface in the Iron-based superconductor
We have carried out first principles all-electron calculations of the
(001)-projected 2D electron momentum density and the directional Compton
profiles along the [100], [001] and [110] directions in the Fe-based
superconductor LaOFeAs within the framework of the local density approximation.
We identify Fermi surface features in the 2D electron momentum density and the
directional Compton profiles, and discuss issues related to the observation of
these features via Compton scattering experiments.Comment: 4 pages, 3 figure
Bulk Fermi surface and momentum density in heavily doped LaSrCuO using high resolution Compton scattering and positron annihilation spectroscopies
We have observed the bulk Fermi surface (FS) in an overdoped (=0.3) single
crystal of LaSrCuO by using Compton scattering. A
two-dimensional (2D) momentum density reconstruction from measured Compton
profiles yields a clear FS signature in the third Brillouin zone along [100].
The quantitative agreement between density functional theory (DFT) calculations
and momentum density experiment suggests that Fermi-liquid physics is restored
in the overdoped regime. In particular the predicted FS topology is found to be
in good accord with the corresponding experimental data. We find similar
quantitative agreement between the measured 2D angular correlation of positron
annihilation radiation (2D-ACAR) spectra and the DFT based computations.
However, 2D-ACAR does not give such a clear signature of the FS in the extended
momentum space in either the theory or the experiment.Comment: 9 pages, 8 figure
Characterization of preplasma produced by an ultrahigh intensity laser system
Copyright 2004 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Plasmas, 11(8), 3721-3725, 2004 and may be found at http://dx.doi.org/10.1063/1.176077
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