Impurity magnetic moments in unconventional superconductors

An impurity in an unconventional superconductor strongly perturbs the order parameter out to distances of order ξ(T); when the order parameter breaks time-reversal symmetry, a pattern of supercurrents J(R) is set up in the vicinity of the impurity. In this paper we address the question of whether J(R) integrates up to produce a net magnetic moment. In a wide variety of situations the moment vanishes, if the perturbation in the order parameter goes to zero rapidly enough at large distances from the impurity