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Local lattice distortions and thermal transport in perovskite manganites
Measurements of thermal conductivity versus temperature and magnetic field are reported for perovskite manganites that exhibit ferromagnetic (FM), charge-ordering (CO), antiferromagnetic, and/or structural phase transitions. The data reveal a dominant lattice contribution to the heat conductivity with {kappa}{approximately}1{minus}2 W/mK near room temperature. The rather low values, implying a phonon mean free path on the order of a lattice spacing, are shown to correlate with static local distortions of the MnO{sub 6} octahedra. Modifications of the local structure are responsible for abrupt anomalies in the zero-field {kappa} at the FM, CO, and structural transitions, and for colossal magnetothermal resistance near the FM transition. {copyright} {ital 1997} {ital The American Physical Society
TRANSPORT CRITICAL CURRENT DENSITIES OF PARTIALLY ALIGNED BULK SAMPLES OF YBA2CU3O7-X SUPERCONDUCTORS
TRANSPORT CRITICAL CURRENT DENSITIES OF PARTIALLY ALIGNED BULK SAMPLES OF YBA2CU3O7-X SUPERCONDUCTORS
Pathological Biominerals: Raman and Infrared Studies of Bioapatite Deposits in Human Heart Valves
STUDY OF Y-Ba-Cu-O SUPERCONDUCTORS PREPARED WITH THE OXALATE PRECIPITATION/EVAPORATION METHOD
A study is presented on a series of Y-Ba-Cu-O superconductors prepared
with the Oxalate Precipitation/Evaporation method. The effect of the
preparation conditions on the properties of these superconductors has
been studied with X-rays, scanning electron microscopy, Raman
spectroscopy, and magnetic measurements. The experiments show that good
quality superconductors can be fabricated with this preparation
procedure and also indicate that the properties of these materials are
very sensitive to the preparation conditions