Polarized neutron scattering studies of magnetic excitations in electron-overdoped superconducting BaFe1.85Ni0.15As2

Mengshu Liu, C. Lester, Jiri Kulda, Xinye Lu, Huiqian Luo, Meng Wang, S. M. Hayden, Pengcheng Dai

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Abstract

We use polarized inelastic neutron scattering to study low-energy spin excitations and their spatial anisotropy in electron-overdoped superconducting BaFe1.85Ni0.15As2 (T-c = 14 K). In the normal state, the imaginary part of the dynamic susceptibility chi '' (Q,omega) at the antiferromagnetic wave vector Q = (0.5,0.5,1) increases linearly with energy for E <= 13 meV. Upon entering the superconducting state, a spin gap opens below E approximate to 3 meV and a broad neutron spin resonance appears at E approximate to 7 meV. Our careful neutron polarization analysis reveals that chi ''(Q,omega) is isotropic for the in-plane and out-of-plane components in both the normal and superconducting states. A comparison of these results with those of undoped BaFe2As2 and optimally electron-doped BaFe1.9Ni0.1As2 (T-c = 20 K) suggests that the spin anisotropy observed in BaFe1.9Ni0.1As2 is likely due to its proximity to the undoped BaFe2As2. Therefore, the neutron spin resonance is mostly isotropic in the optimal and electron overdoped iron pnictides, consistent with a singlet to triplet excitation and isotropic paramagnetic scattering.

Original languageEnglish
Article number214516
Pages (from-to)-
Number of pages7
JournalPhysical Review B: Condensed Matter and Materials Physics
Volume85
Issue number21
DOIs
Publication statusPublished - 18 Jun 2012

Keywords

  • cond-mat.supr-con

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