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Neutron-Scattering Measurements of Spin Excitations in LaFeAsO and Ba(Fe0.953Co0.047)2As2: Evidence for a Sharp Enhancement of Spin Fluctuations by Nematic Order



Qiang Zhang, Rafael M. Fernandes, Jagat Lamsal, Jiaqiang Yan, Songxue Chi, Gregory S. Tucker, Daniel K. Pratt, Jeffrey W. Lynn, R. W. McCallum, P. C. Canfield, Thomas A. Lograsso, Alan Goldman, David Vaknin, Robert J. McQueeney


Inelastic neutron scattering was employed to investigate the impact of electronic nematic order on the magnetic spectra of LaFeAsO and Ba(Fe0.9536Cod0.047)2As2. These materials are ideal to study the paramagnetic-nematic state, since the nematic order, signaled by the tetragonal-to-orthorhombic transition at the temperature Ts, sets in well above the stripe antiferromagnetic ordering temperature TN. We find in both systems that the temperature-dependent dynamic susceptibility displays an anomaly at TS followed by a sharp enhancement in the spin-spin correlation length, revealing a strong feedback effect of nematic order on the low-energy magnetic spectrum. Our findings can be consistently described by a model that attributes the structural/nematic transition to magnetic fluctuations, and unveils the key role played by nematic order in promoting the long-range stripe antiferromagnetic order in pnictides.
Physical Review Letters


Superconductor, correlated electrons, magnetic correlations, inelastic neutron scattering, nematic order, dynamic correlation range, iron superconductor


Zhang, Q. , Fernandes, R. , Lamsal, J. , Yan, J. , Chi, S. , Tucker, G. , Pratt, D. , Lynn, J. , McCallum, R. , Canfield, P. , Lograsso, T. , Goldman, A. , Vaknin, D. and McQueeney, R. (2015), Neutron-Scattering Measurements of Spin Excitations in LaFeAsO and Ba(Fe<sub>0.953</sub>Co<sub>0.047</sub>)<sub>2</sub>As<sub>2</sub>: Evidence for a Sharp Enhancement of Spin Fluctuations by Nematic Order, Physical Review Letters, [online], (Accessed July 23, 2024)


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Created February 3, 2015, Updated October 12, 2021