Research Article

Frontiers of Physics in China

, Volume 5, Issue 2, pp 161-165

Low-energy Ce spin excitations in CeFeAsO and CeFeAsO0.84F0.16

  • Shi-liang Li李世亮Affiliated withBeijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of SciencesDepartment of Physics and Astronomy, The University of Tennessee
  • , Dao-xin Yao姚道新Affiliated withDepartment of Physics, Purdue University
  • , Yi-ming Qiu邱义铭Affiliated withNIST Center for Neutron Research, National Institute of Standards and TechnologyDepartment of Materials Science and Engineering, University of Maryland
  • , Hye Jung KangAffiliated withDepartment of Physics and Astronomy, Clemson University
  • , E. W. CarlsonAffiliated withDepartment of Physics, Purdue University
  • , Jiang-ping Hu胡江平Affiliated withDepartment of Physics, Purdue University
  • , Gen-fu Chen陈根富Affiliated withDepartment of Phyiscs, Renmin University of China
  • , Nan-lin Wang王楠林Affiliated withBeijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences
  • , Peng-cheng Dai戴鹏程Affiliated withBeijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of SciencesDepartment of Physics and Astronomy, The University of TennesseeNeutron Scattering Sciences Division, Oak Ridge National Laboratory Email author 

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Abstract

We use inelastic neutron scattering to study the low-energy spin excitations of polycrystalline samples of nonsuperconducting CeFeAsO and superconducting CeFeAsO0.84F0.16. Two sharp dispersionless modes are found at 0.85 and 1.16 meV in CeFeAsO below the Ce antiferromagnetic (AF) ordering temperature of T N Ce ˜ 4 K. On warming to above T N Ce ˜ 4 K, these two modes become one broad dispersionless mode that disappears just above the Fe ordering temperature T N Fe ˜ 140 K. For superconducting CeFeAsO0.84F0.16, where Fe static AF order is suppressed, we find a weakly dispersive mode center at 0.4 meV that may arise from short-range Ce-Ce exchange interactions. Using a Heisenberg model, we simulate powder-averaged Ce spin wave excitations. Our results show that we need both Ce spin wave and crystal electric field excitations to account for the whole spectra of low-energy spin excitations.

Keywords

iron pnictides rare earth spin waves crystal field

PACS numbers

71.70.Ch 75.30.Ds 74.25.Ha