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Low energy spin waves and magnetic interactions in SrFe2As2

We report inelastic neutron scattering studies of magnetic excitations in antiferromagnetically ordered SrFe2As2 (T_{N}=200-220 K), the parent compound of the FeAs-based superconductors. At low temperatures (T=7 K), the magnetic spectrum S(Q,Planck's omega) consists of a Bragg peak at the elast...

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Bibliographic Details
Published in:Physical review letters 2008-10, Vol.101 (16), p.167203-167203
Main Authors: Zhao, Jun, Yao, Dao-Xin, Li, Shiliang, Hong, Tao, Chen, Y, Chang, S, Ratcliff, 2nd, W, Lynn, J W, Mook, H A, Chen, G F, Luo, J L, Wang, N L, Carlson, E W, Hu, Jiangping, Dai, Pengcheng
Format: Article
Language:English
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Summary:We report inelastic neutron scattering studies of magnetic excitations in antiferromagnetically ordered SrFe2As2 (T_{N}=200-220 K), the parent compound of the FeAs-based superconductors. At low temperatures (T=7 K), the magnetic spectrum S(Q,Planck's omega) consists of a Bragg peak at the elastic position (Planck's omega=0 meV), a spin gap (Delta< or =6.5 meV), and sharp spin-wave excitations at higher energies. Based on the observed dispersion relation, we estimate the effective magnetic exchange coupling using a Heisenberg model. On warming across T_{N}, the low-temperature spin gap rapidly closes, with weak critical scattering and spin-spin correlations in the paramagnetic state. The antiferromagnetic order in SrFe2As2 is therefore consistent with a first order phase transition, similar to the structural lattice distortion.
ISSN:0031-9007
DOI:10.1103/PhysRevLett.101.167203