Spin-echo observation of radio frequency induced flux lattice annealing (RIFLA) in a type-II superconductor

We report the annealing of a strained flux line lattice (FLI) in 10 mu m di ameter type-II superconcducting NbTi filaments by an rf magnetic field at 4 .2 K in a magnetic field of 1 T. The strained FLL is prepared by slowly cha nging the direction of the applied magnetic field When the rf magnetic fiel d used to generate a Nb-93 NMR spin echo anneals the FLL, there is a corres ponding reduction in the amplitude of the spin echo. Starting from an annea led condition, a rotation threshold of 3 mr is needed to produce enough FLL strain to be observed in these measurements.