Biaxial magnetic alignment in twinned REBa[2]Cu[3]O[y]superconductors

Biaxial magnetic alignment of REBa[2]Cu[3]O[y] (RE123, RE = Y, Nd, Sm, Dy, and Er) superconductor powders containing twin microstructures was demonstrated. Appropriate choice of RE effectively improved the degrees of in-plane and c-axis orientation in RE123 powder samples aligned under modulated rotating magnetic fields at room temperature. From the relationship between the magnetic field strength and the degrees of orientation, it is concluded that heavy RE ions induced the improvement of the in-plane magnetic anisotropies in RE123 grains with twin microstructures

Superconductivity in Pr2Ba4Cu7O15-delta with metallic double chains

We report superconductivity with $T_{c,onset}$=$\sim$10K in Pr$_{2}$Ba$_{4}$Cu$_{7}$O$_{15-\delta}$ compound possessing metallic double chains. A reduction treatment on as-sintered samples causes not only the enhanced metallic conduction but also the appearance of superconductivity accompanied by the c-axis elongation due to oxygen deficiency

Optical conductivity in the CuO double chains of PrBa_2Cu_4O_8: Consequences of charge fluctuation

We calculate the optical conductivity of the CuO double chains of PrBa$_2$Cu$_4$O$_8$ by the mean-field approximation for the coupled two-chain Hubbard model around quarter filling. We show that the $\sim$40 meV peak structure, spectral shape, and small Drude weight observed in experiment are reproduced well by the present calculation provided that the stripe-type charge ordering presents. We argue that the observed anomalous optical response may be due to the presence of stripe-type fluctuations of charge carriers in the CuO double chains; the fast time scale of the optical measurement should enable one to detect slowly fluctuating order parameters as virtually a long-range order.Comment: 7 pages, 5 eps figure

Spin dynamics and antiferromagnetic order in PrBa2Cu4O8 studied by Cu nuclear respnance

Results of the nuclear resonance experiments for the planar Cu sites in PrBa2Cu4O8 are presented. The NMR spectrum at 1.5 K in zero magnetic field revealed an internal field of 6.1 T, providing evidence for an antiferromagnetic order of the planar Cu spins. This confirms that the CuO2 planes are insulating, therefore, the metallic conduction in this material is entirely due to the one-dimensional zigzag Cu2O2 chains. The results of the spin-lattice relaxation rates measured by zero field NQR above 245 K in the paramagnetic state are explained by the theory for a Heisenberg model on a square lattice.Comment: 4 pages, 2 figure

An Asian emission inventory of anthropogenic emission sources for the period 1980?2020

International audienceWe developed a new emission inventory for Asia (Regional Emission inventory in ASia (REAS) Version 1.1) for the period 1980?2020. REAS is the first inventory to integrate historical, present, and future emissions in Asia on the basis of a consistent methodology. We present here emissions in 2000, historical emissions for 1980?2003, and projected emissions for 2010 and 2020 of SO2, NOx, CO, NMVOC, black carbon (BC), and organic carbon (OC) from fuel combustion and industrial sources. Total energy consumption in Asia more than doubled between 1980 and 2003, causing a rapid growth in Asian emissions, by 28% for BC, 30% for OC, 64% for CO, 108% for NMVOC, 119% for SO2, and 176% for NOx. In particular, Chinese NOx emissions showed a marked increase of 280% over 1980 levels, and growth in emissions since 2000 has been extremely high. These increases in China were mainly caused by increases in coal combustion in the power plants and industrial sectors. NMVOC emissions also rapidly increased because of growth in the use of automobiles, solvents, and paints. By contrast, BC, OC, and CO emissions in China showed decreasing trends from 1996 to 2000 because of a reduction in the use of biofuels and coal in the domestic and industry sectors. However, since 2000, Chinese emissions of these species have begun to increase. Thus, the emissions of air pollutants in Asian countries (especially China) showed large temporal variations from 1980?2003. Future emissions in 2010 and 2020 in Asian countries were projected by emission scenarios and from emissions in 2000. For China, we developed three emission scenarios: PSC (policy success case), REF (reference case), and PFC (policy failure case). In the 2020 REF scenario, Asian total emissions of SO2, NOx, and NMVOC were projected to increase substantially by 22%, 44%, and 99%, respectively, over 2000 levels. The 2020 REF scenario showed a modest increase in CO (12%), a lesser increase in BC (1%), and a slight decrease in OC (?5%) compared with 2000 levels. However, it should be noted that Asian total emissions are strongly influenced by the emission scenarios for China

Fragile three-dimensionality in the quasi-one-dimensional cuprate PrBa_2Cu_4O_8

In this article we report on the experimental realization of dimensional crossover phenomena in the chain compound PrBa$_2$Cu$_4$O$_8$ using temperature, high magnetic fields and disorder as independent tuning parameters. In purer crystals of PrBa$_2$Cu$_4$O$_8$, a highly anisotropic three-dimensional Fermi-liquid state develops at low temperatures. This metallic state is extremely susceptible to disorder however and localization rapidly sets in. We show, through quantitative comparison of the relevant energy scales, that this metal/insulator crossover occurs precisely when the scattering rate within the chain exceeds the interchain hopping rate(s), i.e. once carriers become confined to a single conducting element.Comment: 12 pages, 5 figures, published at http://www.iop.org/EJ/article/1367-2630/8/9/172/njp6_9_172.htm

Possible co-existence of local itinerancy and global localization in a quasi-one-dimensional conductor

In the chain compound PrBa$_2$Cu$_4$O$_8$ localization appears simultaneously with a dimensional crossover in the electronic ground state when the scattering rate in the chains exceeds the hopping rate between the chains. Here we report the discovery of a large, transverse magnetoresistance in PrBa$_2$Cu$_4$O$_8$ in the localized regime. This result suggests a novel form of localization whereby electrons retain their metallic (quasi-one-dimensional) character over a microscopic length scale despite the fact that macroscopically, they exhibit localized (one-dimensional) behavior.Comment: 4 pages, 4 Figure