摘要 :
We use bulk magnetic susceptibility, electronic specific heat, and neutron scattering to study structural and magnetic phase transitions in Fe_(1+y)Se_xTe_(1-x)Fe_(1.068)Te exhibits a first-order phase transition near 67 K with a ...
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We use bulk magnetic susceptibility, electronic specific heat, and neutron scattering to study structural and magnetic phase transitions in Fe_(1+y)Se_xTe_(1-x)Fe_(1.068)Te exhibits a first-order phase transition near 67 K with a tetragonal-to-monoclinic structural transition and simultaneously develops a collinear antiferromagnetic (AF) order responsible for the entropy change across the transition. Systematic studies of the FeSe_(1-x)Te_x. system reveal that the AF structure and lattice distortion in these materials are different from those of FeAs-based pnictides. These results call into question the conclusions of present density-functional calculations, where FeSe_(1-x)Te_x and Fe As-based pnictides are expected to have similar Fermi surfaces and therefore the same spin-density wave AF order.
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摘要 :
Recently, high-transition-temperature (high-T_c) superconductivity was discovered in the iron pnictide RFeAsO_(1-x)F_x (R, rare-earth metal) family of materials. We use neutron scattering to study the structural and magnetic phase...
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Recently, high-transition-temperature (high-T_c) superconductivity was discovered in the iron pnictide RFeAsO_(1-x)F_x (R, rare-earth metal) family of materials. We use neutron scattering to study the structural and magnetic phase transitions in CeFeAsO_(1-x)F_x as the system is tuned from a semimetal to a high-T_c superconductor through fluorine (F) doping, x. In the undoped state, CeFeAsO develops a structural lattice distortion followed by a collinear antiferromagnetic order with decreasing temperature. With increasing fluorine doping, the structural phase transition decreases gradually and vanishes within the superconductivity dome near x = 0.10, whereas the antiferromagnetic order is suppressed before the appearance of superconductivity for x > 0.06, resulting in an electronic phase diagram remarkably similar to that of the high-T_c copper oxides. Comparison of the structural evolution of CeFeAsO_(1-x)F_x with other Fe-based superconductors suggests that the structural perfection of the Fe-As tetrahedron is important for the high-T_c superconductivity in these Fe pnictides.
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摘要 :
We use powder neutron diffraction to study the spin and lattice structures of polycrystalline samples of nonsuperconducting PrFeAsO and superconducting PrFeAsO_(0.85)F_(0.15) and PrFeAsO_(0.85).We find that PrFeAsO exhibits abrupt...
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We use powder neutron diffraction to study the spin and lattice structures of polycrystalline samples of nonsuperconducting PrFeAsO and superconducting PrFeAsO_(0.85)F_(0.15) and PrFeAsO_(0.85).We find that PrFeAsO exhibits abrupt structural phase transitions at 153 K followed by static long-range antiferromagnetic order at 127 K. Both the structural distortion and magnetic order are similar to other rare-earth oxypnictides. Electron doping the system with either fluorine or oxygen deficiency suppresses the structural distortion and static long-range antiferromagnetic order, therefore placing these materials into the same class of FeAs-based superconductors.
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