Abstract
We report inelastic neutron scattering studies of magnetic excitations in antiferromagnetically ordered SrFe2As2 (TN=200–220 K), the parent compound of the FeAs-based superconductors. At low temperatures (T=7 K), the magnetic spectrum S(Q,[h-bar]omega) consists of a Bragg peak at the elastic position ([h-bar]omega=0 meV), a spin gap (Delta<=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 TN, 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.
Published in:
Physical Review Letters 101,16 ( 2008 )
Date of Version
January 2008
Recommended Citation
Zhao, J.; Yao, D. X.; Li, S. L.; Hong, T.; Chen, Y.; Chang, S.; Ratcliff, W.; Lynn, J. W.; Mook, H. A.; Chen, G. F.; Luo, J. L.; Wang, N. L.; Carlson, E. W.; Hu, J. P.; and Dai, P. C., "Low Energy Spin Waves and Magnetic Interactions in SrFe2As2" (2008). Department of Physics and Astronomy Faculty Publications. Paper 927.
https://docs.lib.purdue.edu/physics_articles/927