Investigations of Magnetic Behavior in Various Multifilamentary Wires by Means of the 1st and 3rd Harmonics of the AC Magnetic Susceptibility

The 1st and 3rd harmonics of the AC magnetic susceptibility were measured as a function of the temperature on Nb₃Sn multifilamentary wires, produced by different processes: bronze route (home made) and internal tin diffusion (Oxford) These measurements were performed both with and without a DC magnetic field, up to 19T. We observed that the magnetic response of the bronze route wire is mainly characterized by vortex dynamical phenomena, such as flux creep. This is in contrast with the internal tin wire, where the static hysteretic Bean model is sufficient to describe the magnetic behavior. Moreover, by using the 3rd harmonics measurements, it has been possible to get indication about the phase transition in the vortex lattice between the Bragg Glass phase and the disordered phase, which is absent in the bronze route multifilamentary wire. The H-T phase diagram has been obtained for both samples and has been compared with the previously analyzed one for the Nb₃Sn single crystals and polycrystalline samples