Structure, spin glass, and spin state in perovskite GdCo/sub 1-x/Mn/sub x/O/sub 3/ (x /spl les/ 0.5)
Perovskite GdCo/sub 1-x/Mn/sub x/O/sub 3/ (x=0.2,0.3,0.4,0.5) compounds have been prepared by solid-state reaction. Structures were characterized using X-ray diffraction and Rietveld Refinement method. The compounds crystallized in orthorhombic with Plmn space group. Crystal lattices decreased with the increase of Mn doping level. DC magnetization and ac susceptibility were studied over a wide temperature range and different frequencies. A typical spin glass state was observed in all samples around the same temperature of 122 K where the compounds turned from paramagnetic to ferromagnetic states. For x<0.5, secondary transitions were observed both in dc and ac measurement which were independent of frequency but depended on doping level. The valences of Co or Mn with possible spin states were estimated.
Synthesis and characterization of Ln(B0.5Mn0.5)O3 (Ln-lanthanoid; B = Ni, Co) perovskites
Abstract The Ln(B0.5Mn0.5)O3 (Ln-lanthanoid; B = Ni, Co) compounds with the orthorhombic perovskite structure have been prepared by a solid state reaction. They are ferromagnets with relatively high Curie temperatures. The Curie temperature decreases with decreasing average radii of the Ln-ion. It is shown that the Ln(Co0.5Mn0.5)O3 (Ln = Gd, Tb, Dy, Y, Ho) are metamagnets.
Deliberative Democracy and the Resource Curse: A Nationwide Experiment in Tanzania
Oil and gas discoveries in developing countries are often associated with short-sighted economic policies and, in response, calls to insulate resource management from populist impulses. We report on a randomized experiment testing methods to overcome this apparent tension between sound resource governance and democratic politics. Soon after Tanzania’s discovery of major natural gas reserves, we invited a nationally representative sample of voters to an intensive public deliberation of policy options featuring nationally recognized experts and small-group discussions. Democratic deliberation reinforced the public’s strong preference for rapid spending of gas revenues, but also increased support for various prudential and economically orthodox measures, including independent oversight of gas revenues, limits on government borrowing, and selling gas abroad rather than subsidizing fuel at home. These effects were driven by deliberation per se, rather than a pure information treatment, and show no evidence of contamination by facilitatoror peer-effects in group deliberations. www.cgdev.org Justin Sandefur, Nancy Birdsall, James Fishkin, and Mujobu Moyo