Larsen, J. Mencia Uranga, B. Stieper, G. Holm, S. L. Bernhard, Christian Wolf, T. Lefmann, K. Andersen, B. M. Niedermayer, Christof 2015-01-13 We have studied the magnetic and superconducting properties of Ba(Fe0.95Co0.05)2As2 as a function of temperature and external magnetic field using neutron scattering and muon spin rotation. Below the superconducting transition temperature the magnetic and superconducting order parameters coexist and compete. A magnetic field can significantly enhance the magnetic scattering in the superconducting state, roughly doubling the Bragg intensity at 13.5 T. We perform a microscopic modeling of the data by use of a five-band Hamiltonian relevant to iron pnictides. In the superconducting state, vortices can slow down and freeze spin fluctuations locally. When such regions couple they result in a long-range ordered antiferromagnetic phase producing the enhanced magnetic elastic scattering in agreement with experiments. application/pdf https://folia.unifr.ch/global/documents/304275 https://folia.unifr.ch/documents/304275/files/ber_csm.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1103/PhysRevB.91.024504 info:eu-repo/semantics/openAccess License undefined Physical Review B. - 2015, vol. 91, no. 2, p. 024504 info:eu-repo/classification/udc/53 Competing superconducting and magnetic order parameters and field-induced magnetism in electron-doped $\mathrm{Ba}{({\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x})}_{2}{\mathrm{As}}_{2}$ http://purl.org/coar/resource_type/c_6501