2008/06/30 by Peng Cheng, Huan Yang, Ying Jia +5 · 4 citations
Materials Science · Physics and Astronomy · #Condensed matter physics #Density of states #Hall effect #Iron-based superconductors research #Magnetic field #Magnetoresistance #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Rare-earth and actinide compounds #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.78.134508
published as Phys. Rev. B 78, 134508 (2008). · 8 pages, 9 figures
arxiv created 2008/09/09 · openalex publication_date 2008/10/08 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Hall effect and magnetoresistance have been measured on single crystals of NdFeAsO_1\ensuremath-xFx with x=0 (Tc=0 K) and x=0.18 (Tc=50 K). For the undoped samples, strong Hall effect and magnetoresistance with strong temperature dependence were found below about 150 K. The magnetoresistance was found to be as large as 30% at 15 K at a magnetic field of 9 T. From the transport data we found that the transition near 155 K was accomplished in two steps: first one occurs at 155 K which may be associated with the structural transition, the second one takes place at about 140 K which may correspond to the spin-density-wave-like transition. In the superconducting sample with Tc=50 K, it is found that the Hall coefficient also reveals a strong temperature dependence with a negative sign. But the magnetoresistance becomes very weak and does not satisfy Kohler's scaling law. These dilemmatic results (strong Hall effect and very weak magnetoresistance) prevent understanding of the normal-state electric conduction by a simple multi-band model by taking into account the electron and hole pockets. Detailed analysis further indicates that the strong temperature dependence of RH cannot be easily understood with the simple multi-band model either. A picture concerning a suppression to the density of states at the Fermi energy in lowering temperature is more reasonable. A comparison between the Hall coefficient of the undoped sample and the superconducting sample suggests that the doping may remove the nesting condition for the formation of the spin-density wave order, since both samples have very similar temperature dependence above 175 K.