Antiferromagnetic spin excitations in single crystals of   nonsuperconducting Li1-xFeAs
  We use neutron scattering to determine spin excitations in single crystals of nonsuperconducting Li1-xFeAs throughout the Brillouin zone. Although angle resolved photoemission experiments and local density approximation calculations suggest poor Fermi surface nesting conditions for antiferromagnetic(AF) order, spin excitations in Li1-xFeAs occur at the AF wave vectors Q = (1, 0) at low energies, but move to wave vectors Q = (\pm 0.5, \pm0.5) near the zone boundary with a total magnetic bandwidth comparable to that of BaFe2As2. These results reveal that AF spin excitations still dominate the low-energy physics of these materials and suggest both itinerancy and strong electron-electron correlations are essential to understand the measured magnetic excitations. 
Meng Wang, X. C. Wang, D. L. Abernathy, L. W. Harriger, H. Q. Luo,   Yang Zhao, J. W. Lynn, Q. Q. Liu, C. Q. Jin, Chen Fang,...
cond-mat.supr-con