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Chapman JP Attfield JP Rodriguez-Martinez LM Lezama L Rojo T 《Dalton transactions (Cambridge, England : 2003)》2004,(19):3026-3031
Doped manganite perovskites AMnO(3) exhibit a rich variety of electronic properties, resulting from the interplay of charge (Mn(3+)/Mn(4+)), spin (Mn magnetic moment) and orbital (Mn(3+) Jahn-Teller distortion) degrees of freedom. Magnetisation measurements and ESR spectra have been used to study a series of eight AMnO(3) perovskites, in which the A cation sites are occupied by a distribution of 70% trivalent lanthanide and 30% divalent Ca, Sr or Ba ions. These all have a mean A cation radius of 1.20 Angstrom but different values of the cation size variance sigma(2). A change from orbital disorder to order (cooperative Jahn-Teller distortions) was previously found in the insulating regime at sigma(2) = approximately 0.005 Angstrom(2). This work has shown that co-existence of the orbitally ordered and disordered phases is found in sigma(2)= 0.0016-0.0040 Angstrom(2) samples, with a difference of 40 K between their Curie temperatures. This is ascribed to competition between orbital ordering and microstructural lattice strains. At larger sigma(2) > 0.005 Angstrom(2), the orbital ordering strains are dominant and only this phase is observed. This intermediate temperature phase segregation is one of many strain-driven separation phenomena in manganites. 相似文献
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High pressure synthesis of late rare earth RFeAs(O,F) superconductors; R = Tb and Dy 总被引:1,自引:0,他引:1
Bos JW Penny GB Rodgers JA Sokolov DA Huxley AD Attfield JP 《Chemical communications (Cambridge, England)》2008,(31):3634-3635
New TbFeAs(O,F) and DyFeAs(O,F) superconductors with critical temperatures T(c) = 46 and 45 K and very high critical fields, >/=100 T, have been prepared at 1100-1150 degrees C and 10-12 GPa, demonstrating that high pressure may be used to synthesise late rare earth derivatives of the recently reported RFeAs(O,F) (R = La-Nd, Sm, Gd) high temperature superconductors. 相似文献
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Conservative methods for the Toda lattice equations 总被引:1,自引:0,他引:1
We are concerned with the numerical integration of the Todalattice equations by using different conservative methods. Numericalexperiments suggest that the global error for isospectral schemesdecreases exponentially with time but it is almost constantfor either symplectic or more general integrators. We providea theoretical explanation for these experimental findings. 相似文献
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McLaughlin AC Begg L Harrow C Kimber SA Sher F Attfield JP 《Journal of the American Chemical Society》2006,128(38):12364-12365
A remarkable variety of conducting states has been found in RuSr2(R2-xCex)Cu2O10-delta ruthenocuprates by tuning the properties of the magnetic CuO2 and RuO2 layers through small changes in the chemistry of the (R,Ce)2O2-delta slab. Both the R3+ cation size and the charge transfer determined by the R/Ce ratio and the oxygen deficiency delta are important controlling parameters that tune ground-state properties from positive magnetoresistive to negative magnetoresistive to superconducting. 相似文献