Probing the Superconducting Vortex Structure by Polarized-μ+Spin Precession

Abstract

The magnetic field structure of vortices in the mixed state of a lead-indium alloy and of niobium was probed by stopped ${\mu }^{+}$ particles. Fourier transforms of time-dependent spin-precession data contain a peak at the average internal field, which is also the applied field. For the alloy only there is a second peak at the saddle point of the internal field distribution. Motional averaging due to quantum diffusion of the muons at low temperatures can account for these results.