Re-entry in ferromagnetic superconductors

The re-entry phenomenon in magnetic superconductors is studied using the generalized Ginzburg-Landau free energy introduced by Blount and Varma. The re-entry temperature Tsub(c2) is simply that temperature at which the magnetization acts as a source of induction strong enough to destroy superconductivity. Above Tsub(c2) ferromagnetism and superconductivity coexist. The structure is an Abrikosov vortex lattice, with ferromagnetic magnetization spreading widely around the vortex cores. Within the approximations, the phase transition at Tsub(c2) is of second order. (author)