Disentangling superconducting and magnetic orders in NaFe1−xNixAs using muon spin rotation Academic Article uri icon

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abstract

  • Muon spin rotation and relaxation studies have been performed on a "111" family of iron-based superconductors NaFe_1-xNi_xAs. Static magnetic order was characterized by obtaining the temperature and doping dependences of the local ordered magnetic moment size and the volume fraction of the magnetically ordered regions. For x = 0 and 0.4 %, a transition to a nearly-homogeneous long range magnetically ordered state is observed, while for higher x than 0.4 % magnetic order becomes more disordered and is completely suppressed for x = 1.5 %. The magnetic volume fraction continuously decreases with increasing x. The combination of magnetic and superconducting volumes implies that a spatially-overlapping coexistence of magnetism and superconductivity spans a large region of the T-x phase diagram for NaFe_1-xNi_xAs . A strong reduction of both the ordered moment size and the volume fraction is observed below the superconducting T_C for x = 0.6, 1.0, and 1.3 %, in contrast to other iron pnictides in which one of these two parameters exhibits a reduction below TC, but not both. The suppression of magnetic order is further enhanced with increased Ni doping, leading to a reentrant non-magnetic state below T_C for x = 1.3 %. The reentrant behavior indicates an interplay between antiferromagnetism and superconductivity involving competition for the same electrons. These observations are consistent with the sign-changing s-wave superconducting state, which is expected to appear on the verge of microscopic coexistence and phase separation with magnetism. We also present a universal linear relationship between the local ordered moment size and the antiferromagnetic ordering temperature TN across a variety of iron-based superconductors. We argue that this linear relationship is consistent with an itinerant-electron approach, in which Fermi surface nesting drives antiferromagnetic ordering.

authors

  • Cheung, Sky C
  • Guguchia, Zurab
  • Frandsen, Benjamin A
  • Gong, Zizhou
  • Yamakawa, Kohtaro
  • Almeida, Dalson E
  • Onuorah, Ifeanyi J
  • Bonfá, Pietro
  • Miranda, Eduardo
  • Wang, Weiyi
  • Tam, David W
  • Song, Yu
  • Cao, Chongde
  • Cai, Yipeng
  • Hallas, Alannah M
  • Wilson, Murray N
  • Munsie, Timothy JS
  • Luke, Graeme
  • Chen, Bijuan
  • Dai, Guangyang
  • Jin, Changqing
  • Guo, Shengli
  • Ning, Fanlong
  • Fernandes, Rafael M
  • De Renzi, Roberto
  • Dai, Pengcheng
  • Uemura, Yasutomo J

publication date

  • June 12, 2018