抄録
The magnetic transition of Sn–In alloys at temperatures near the critical temperature range became broad with the increase of temperature for alloys with more than about 1.6 at. % In (nominal), which showed magnetic hysteresis with trapped flux. These alloys did not have well-defined critical temperatures and the superconducting transition occurred in certain critical temperature ranges. These behaviours are thought to be due to the inhomogeneous distribution of impurities. In the most dilute alloy—Sn-0.38 at. % In (nominal)—specimen, the superconducting nucleation field Hc3 exceeded the thermodynamical critical field Hc and supercooling occurred at lower temperatures. However, its supercooling field for the bulk Hs was nearly equal to Hc3 near the critical temperature. This result is in agreement with the calculations by Feder and by Park. Energy gap obtained from the magnetization with Toxen’s formula approached the BCS value, 3.5 kTc as the impurity increased.
