Current driven pinning strength in the vortex lattice of Nb3Sn aided by   a small oscillating magnetic field
  By the application of a small oscillating magnetic field parallel to the main magnetic field and perpendicular to the transport current, we were able to generate a voltage dip in the I-V curves of Nb$_3$Sn similar to the peak-effect pattern observed in earlier resistivity measurements. The pattern was history dependent and exhibited a memory effect. In addition we observed in the I-V curves for a high shaking-field amplitude a step feature of unknown origin. 
M. Reibelt and N. Toyota
cond-mat.supr-con