Nuclear Magnetic Resonance Studies of Type II Superconductors

ABSTRACTThe results of nuclear magnetic resonance (nmr) experiments on simple type–I superconductors were among the first and most important verifications of the BCS theory of superconductivity. In this paper, the application of nmr techniques to the study of superconducting properties in the more complex type–II superconductors will be reviewed. The discussion will include the effect of material parameters (e.g., degree of long range crystalline order, density of states at the Fermi level, effects of magnetic dopants) on the superconducting properties, including size of the superconducting gap, vortex structure, upper–critical field Hc2, and variations in Tc. Emphasis will be placed on high Tc, high Hc2 materials, i.e., A15 compounds and the ternary Chevrel phases.