Abstract
We investigate the effects of magnetic impurities in a superconducting state with s± pairing symmetry. Within a two-band model, we find that the intra-band magnetic scattering serves as a pair breaker while the inter-band magnetic scattering preserves pairing and hardly affects transition temperature in the Born limit. We also show that the same physics can persist beyond the weak-scattering region. Our results coincide with recent experimental measurements in iron-based superconductors and thus provides an indirect evidence of the possible s± pairing symmetry in these materials.