A study was made of neutron scattering from the flux line lattice in MgB2. Between 0.5 and 0.9T the flux line lattice underwent a 30º reorientation, and simultaneously the scattered intensity falls sharply consistent with the weaker superconducting π band being suppressed with increasing field. It was speculated that the π and σ bands favor different flux line lattice orientations, and that the reorientation was driven by the suppression of the π band. When the c axis of the crystal was rotated 45º to the applied field the penetration depth anisotropy could be measured, and rises both as a function of applied field and temperature.

Effects of Two-Band Superconductivity on the Flux-Line Lattice in Magnesium Diboride. R.Cubitt, M.R.Eskildsen, C.D.Dewhurst, J.Jun, S.M.Kazakov, J.Karpinski: Physical Review Letters, 2003, 91[4], 047002 (3pp)