The Intermediate State in Type I Superconductors
The application of intermediate-state structures theory to V. Sharvin's experiments in oblique fields has provided the most reliable values of surface energy. Sharvin and V. F. Gantmakher determined the anisotropy of surface energy in single crystals. They employed two methods. First, they studied the equilibrium shape of superconducting domains. Second, they measured torques on a sphere in the intermediate state. They concluded that the surface energy varied by more than 12% from one crystal plane to another. Sharvin has pointed out that the motion of normal regions in a dynamic intermediate state involves a transport in entropy, and should produce a temperature difference. The intermediate state of First type superconductors and the mixed state of second type superconductors both represent modes of gradual transition between the superconducting and normal states. The magnetoresistive-probe technique has also been used to investigate intermediate-state structures in hollow cylinders, field distribution within a current-carrying cylinder and macroscopic field gradients within second type superconductors.