Magnetic Hysteresis in Superconducting Thin Films

Tin films were deposited from the vapor at various substrate temperatures and their superconducting properties determined as a function of film structure. Magnetic hysteresis in the superconducting state to normal state phase transition of these films increased with increasing grain size. Hysteresis could be attributed solely to supercooling only in the smaller-grained films deposited at low substrate temperatures. For the larger-grained films, superheating was also observed. The hysteresis observed experimentally was in agreement with the predictions of the Ginzburg-Landau theory of superconductivity.