Mn and Fe impurities in MgB2

Based on first principles calculations, we show that Mn impurities are magnetic in MgB2 due to exchange-splitting of d3z2−1 band. Thus, Mn impurities could act as strong magnetic scattering centres leading to pair-breaking effects in MgB2. In contrast, we find Fe impurities in MgB2 to be nearly non-magnetic.