Field History Effects in Superconducting PbSn Alloys

Abstract

Field history effects in directionally solidified eutectic Pb-Sn alloy specimens are defined and analyzed in terms of the dependence of the flux trapped (at zero applied magnetic field) and the decreasing applied magnetic field minor magnetization paths on magnetic history. The temperature and sweep rate dependence of these effects and the direct measurement of flux profiles along minor magnetization paths may be explained in terms of the hypothesis that the effective pinning force in these specimens depends not only on the nature of the pinning features but also on the density, density distribution, and mobility of defects in the flux line lattice.Feld-Vorbehandlungs-Effekte in gerichtet verfestigten, eutektischen Pb-Sn-Legierungsproben werden definiert und mit der Abhingigkeit der festgesetzten FluBwirbel (bei angelegtem magnetischen Null-Feld) und der kleineren Magnetisierungswege bei abnehmendem magnetischen Feld von der magnetischen Vorbehandlung erkliirt. Die Temperatur-und Geschwindigkeitsabhingigkeit dieser Effekte und die direkte Messung der FluBprofile entlang der kleineren Magnetisierungswege lassen sich mit der Annahme erkliiren, daB die wirksame Anhaftkraft in diesen Proben nicht nur von der Art des Verankerungsmechanismus, sondern auch von der Dichte, der Dichteverteilung und der Beweglichkeit der Defekte im FluBliniengitter abhiingt.

Field history effect of the flux gradient in superconducting niobium

“…Eckert and Handstein 2 observed weak field history effects of the flux density profiles in V3Si single crystals and cold-worked Nb-Ti-Zr samples only near the lower critical field He1. A systematic study of the influence of the field history on the magnetization and trapped flux of eutectic Pb-Sn alloy specimens was published by Schafe et al 3; they observed the effect only in lower fields and suggested an explanation based on defects in the flux line lattice. Kiipfer and Gey, q in analyzing the results for various samples, also observed that the field history effect occurs only at relatively low fields, and suggested that this effect is caused by the defect structure of the flux line lattice.…”