Microwave measurements of the high magnetic field vortex motion pinning parameters in Nb₃Sn

The high frequency vortex motion in Nb₃Sn was analyzed in this work up to 12 T. We used a dielectric loaded resonator tuned at 15 GHz to evaluate the surface impedance Z of a Nb₃Sn bulk sample (24.8 at.%Sn). From the field induced variation of Z, the high frequency vortex parameters (the pinning constant k _p, the depinning frequency ν _p and the flux flow resistivity ρ _ff) were obtained over a large temperature and field range; their field and temperature dependencies were analyzed. Comparison with other superconducting materials shows that high frequency applications in strong magnetic fields are also feasible with Nb₃Sn. In the present work, we report the first measurements about the microwave response in Nb₃Sn in strong magnetic fields. (paper)