Electron doping evolution of the anisotropic spin excitations in BaFe2xNixAs2

Huiqian Luo, Zahra Yamani, Yanchao Chen, Xingye Lu, Meng Wang, Shiliang Li, Thomas A. Maier, Sergey Danilkin, D. T. Adroja, and Pengcheng Dai
Phys. Rev. B 86, 024508 – Published 10 July 2012

Abstract

We use inelastic neutron scattering to systematically investigate the Ni-doping evolution of the low-energy spin excitations in BaFe2xNixAs2 spanning from underdoped antiferromagnet to overdoped superconductor (0.03x0.18). In the undoped state, BaFe2As2 changes from paramagnetic tetragonal phase to orthorhombic antiferromagnetic (AF) phase below about 138 K, where the low-energy (80 meV) spin waves form transversely elongated ellipses in the [H,K] plane of the reciprocal space. Upon Ni doping to suppress the static AF order and induce superconductivity, the c-axis magnetic exchange coupling is rapidly suppressed and the momentum distribution of spin excitations in the [H,K] plane is enlarged in both the transverse and longitudinal directions with respect to the in-plane AF ordering wave vector of the parent compound. As a function of increasing Ni-doping x, the spin excitation widths increase linearly but with a larger rate along the transverse direction. These results are in general agreement with calculations of dynamic susceptibility based on the random phase approximation (RPA) in an itinerant electron picture. For samples near optimal superconductivity at x0.1, a neutron spin resonance appears in the superconducting state. Upon further increasing the electron doping to decrease the superconducting transition temperature Tc, the intensity of the low-energy magnetic scattering decreases and vanishes concurrently with vanishing superconductivity in the overdoped side of the superconducting dome. Comparing with the low-energy spin excitations centered at commensurate AF positions for underdoped and optimally doped materials (x0.1), spin excitations in the overdoped side (x=0.15) form transversely incommensurate spin excitations, consistent with the RPA calculation. Therefore, the itinerant electron approach provides a reasonable description to the low-energy AF spin excitations in BaFe2xNixAs2.

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  • Received 24 May 2012

DOI:https://doi.org/10.1103/PhysRevB.86.024508

©2012 American Physical Society

Authors & Affiliations

Huiqian Luo1, Zahra Yamani2, Yanchao Chen1, Xingye Lu1,3, Meng Wang1, Shiliang Li1, Thomas A. Maier4, Sergey Danilkin5, D. T. Adroja6, and Pengcheng Dai3,1,*

  • 1Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
  • 2Canadian Neutron Beam Centre, National Research Council, Chalk River Laboratories, Chalk River, Ontario K0J 1J0, Canada
  • 3Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA
  • 4Computer Science and Mathematics Division and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
  • 5Bragg Institute, Australian Nuclear Science and Technology Organization, New Illawarra Road, Lucas Heights NSW-2234, Australia
  • 6ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, United Kingdom

  • *pdai@utk.edu

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Issue

Vol. 86, Iss. 2 — 1 July 2012

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