Magnetic order close to superconductivity in the iron-based layered LaO1-xFxFeAs systems
de la Cruz, Clarina; Huang, Q.; Lynn, J. W.; Li, Jiying; II, W. Ratcliff; Zarestky, J. L.; Mook, H. A.; Chen, G. F.; Luo, J. L.; Wang, N. L.; Dai, Pengcheng; de la Cruz, Clarina; Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA; Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA; Huang, Q.; NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA; Lynn, J. W.; NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA; Li, Jiying; NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA; Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742-6393, USA; II, W. Ratcliff; NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA; Zarestky, J. L.; Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA; Mook, H. A.; Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA; Chen, G. F.; Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China; Luo, J. L.; Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China; Wang, N. L.; Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China; Dai, Pengcheng; Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA; Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
Журнал:
Nature
Дата:
2008
Аннотация:
Following the discovery of long-range antiferromagnetic order in the parent compounds of high-transition-temperature (high-Tc) copper oxides, there have been efforts to understand the role of magnetism in the superconductivity that occurs when mobile â electronsâ or â holesâ are doped into the antiferromagnetic parent compounds. Superconductivity in the newly discovered rare-earth iron-based oxide systems ROFeAs (R, rare-earth metal) also arises from either electron or hole doping of their non-superconducting parent compounds. The parent material LaOFeAs is metallic but shows anomalies near 150â K in both resistivity and d.c. magnetic susceptibility. Although optical conductivity and theoretical calculations suggest that LaOFeAs exhibits a spin-density-wave (SDW) instability that is suppressed by doping with electrons to induce superconductivity, there has been no direct evidence of SDW order. Here we report neutron-scattering experiments that demonstrate that LaOFeAs undergoes an abrupt structural distortion below 155â K, changing the symmetry from tetragonal (space group P4/nmm) to monoclinic (space group P112/n) at low temperatures, and then, at â ¼137â K, develops long-range SDW-type antiferromagnetic order with a small moment but simple magnetic structure. Doping the system with fluorine suppresses both the magnetic order and the structural distortion in favour of superconductivity. Therefore, like high-Tc copper oxides, the superconducting regime in these iron-based materials occurs in close proximity to a long-range-ordered antiferromagnetic ground state.
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