Stripe antiferromagnetic spin fluctuations in SrCo₂As ₂

Inelastic neutron scattering measurements of paramagnetic SrCo ₂As₂ at T=5 K reveal antiferromagnetic (AFM) spin fluctuations that are peaked at a wave vector of Q_AFM=(1/2,1/2,1) and possess a large energy scale. These stripe spin fluctuations are similar to those found in AFe₂As₂ compounds, where spin-density wave AFM is driven by Fermi surface nesting between electron and hole pockets separated by Q_AFM. SrCo₂As₂ has a more complex Fermi surface and band-structure calculations indicate a potential instability toward either a ferromagnetic or stripe AFM ground state. The results suggest that stripe AFM magnetism is a general feature of both iron and cobalt-based arsenides and the search for spin fluctuation-induced unconventional superconductivity should be expanded to include cobalt-based compounds.