Competition between stripe and checkerboard magnetic instabilities in   Mn-doped BaFe2As2
  Inelastic neutron scattering measurements on Ba(Fe0.925Mn0.075)2As2 manifest spin fluctuations at two different wavevectors in the Fe square lattice, (1/2,0) and (1/2,1/2), corresponding to the expected stripe spin-density wave order and checkerboard antiferromagnetic order, respectively. Below T_N=80 K, long-range stripe magnetic ordering occurs and sharp spin wave excitations appear at (1/2,0) while broad and diffusive spin fluctuations remain at (1/2,1/2) at all temperatures. Low concentrations of Mn dopants nucleate local moment spin fluctuations at (1/2,1/2) that compete with itinerant spin fluctuations at (1/2,0) and may disrupt the development of superconductivity. 
G. S. Tucker, D. K. Pratt, M. G. Kim, S. Ran, A. Thaler, G. E.   Granroth, K. Marty, W. Tian, J. L. Zarestky, M. D. Lumsden,...
cond-mat.supr-con