Neutron-scattering measurements of spin excitations in LaFeAsO and Ba(Fe(0.953)Co(0.047))(2)As(2): 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; Paul C Canfield; Thomas A Lograsso; Alan I Goldman; David Vaknin; Robert J McQueeney

doi:10.1103/PhysRevLett.114.057001

Neutron-scattering measurements of spin excitations in LaFeAsO and Ba(Fe(0.953)Co(0.047))(2)As(2): evidence for a sharp enhancement of spin fluctuations by nematic order

Phys Rev Lett. 2015 Feb 6;114(5):057001. doi: 10.1103/PhysRevLett.114.057001. Epub 2015 Feb 4.

Authors

Affiliations

¹ Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
² School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA.
³ Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
⁴ NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA.
⁵ Ames Laboratory, Ames, Iowa 50011, USA and Department of Materials Sciences and Engineering, Iowa State University, Ames, Iowa 50011, USA.
⁶ Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA and Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.

PMID: 25699463
DOI: 10.1103/PhysRevLett.114.057001

Abstract

Inelastic neutron scattering is employed to investigate the impact of electronic nematic order on the magnetic spectra of LaFeAsO and Ba(Fe(0.953)Co(0.047))(2)As(2). These materials are ideal to study the paramagnetic-nematic state, since the nematic order, signaled by the tetragonal-to-orthorhombic transition at T(S), sets in well above the stripe antiferromagnetic ordering at T(N). We find that the temperature-dependent dynamic susceptibility displays an anomaly at T(S) 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 or nematic transition to magnetic fluctuations, and unveils the key role played by nematic order in promoting the long-range stripe antiferromagnetic order in iron pnictides.