14,776 research outputs found
Mechanism of magnetostructural transformation in multifunctional MnGaC
MnGaC undergoes a ferromagnetic to antiferromagnetic, volume
discontinuous cubic-cubic phase transition as a function of temperature,
pressure and magnetic field. Through a series of temperature dependent x-ray
absorption fine structure spectroscopy experiments at the Mn K and Ga K edge,
it is shown that the first order magnetic transformation in MnGaC is
entirely due to distortions in Mn sub-lattice and with a very little role for
Mn-C interactions. The distortion in Mn sub-lattice results in long and short
Mn-Mn bonds with the longer Mn-Mn bonds favoring ferromagnetic interactions and
the shorter Mn-Mn bonds favoring antiferromagnetic interactions. At the first
order transition, the shorter Mn-Mn bonds exhibit an abrupt decrease in their
length resulting in an antiferromagnetic ground state and a strained lattice.Comment: Accepted in J. Appl. Phys. Please contact authors for supplementary
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A semiquantitative approach to the impurity-band-related transport properties of GaMnAs nanolayers
We investigate the spin-polarized transport of GaMnAs nanolayers in which a
ferromagnetic order exists below a certain transition temperature. Our
calculation for the self-averaged resistivity takes into account the existence
of an impurity band determining the extended ("metallic" transport) or
localized (hopping by thermal excitation) nature of the states at and near the
Fermi level. Magnetic order and resistivity are inter-related due to the
influence of the spin polarization of the impurity band and the effect of the
Zeeman splitting on the mobility edge. We obtain, for a given range of Mn
concentration and carrier density, a "metallic" behavior in which the transport
by extended carriers dominates at low temperature, and is dominated by the
thermally excited localized carriers near and above the transition temperature.
This gives rise to a conspicuous hump of the resistivity which has been
experimentally observed and brings light onto the relationship between
transport and magnetic properties of this material
SP mountain data analysis
An analysis of synthetic aperture radar data of SP Mountain was undertaken to demonstrate the use of digital image processing techniques to aid in geologic interpretation of SAR data. These data were collected with the ERIM X- and L-band airborne SAR using like- and cross-polarizations. The resulting signal films were used to produce computer compatible tapes, from which four-channel imagery was generated. Slant range-to-ground range and range-azimuth-scale corrections were made in order to facilitate image registration; intensity corrections were also made. Manual interpretation of the imagery showed that L-band represented the geology of the area better than X-band. Several differences between the various images were also noted. Further digital analysis of the corrected data was done for enhancement purposes. This analysis included application of an MSS differencing routine and development of a routine for removal of relief displacement. It was found that accurate registration of the SAR channels is critical to the effectiveness of the differencing routine. Use of the relief displacement algorithm on the SP Mountain data demonstrated the feasibility of the technique
Prevalência do crustáceo Perulernaea gamitanea Thatcher & Paredes, 1985 (Copepoda: Lernaeidae), em Colossoma macropomum (Characidae) e seus híbridos tambacu e tambatinga cultivados na Amazônia Oriental.
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