Influence of trapped magnetic field of Sn-Pb solders on electrical resistivity measurement: an example of superconducting transition of Sn

We examined the affection of the flux-trapped states of Sn60-Pb40 solders on superconducting properties of a Sn wire. The temperature dependence of electrical resistivity at H = 0 Oe after zero-field cooling (ZFC) showed a sharp superconducting transition at T = 3.7 K. In contrast, that after field cooling (FC) resulted in broadening of the transition. The difference between ZFC and FC data evidences critical affection of trapped fluxes at solders on superconducting states. We propose that, in electrical measurements where magnetic fields of several hundred Oe are critical, field experience should be seriously considered when using solders.