Nuclear Magnetic Resonance Investigation of Superconducting and Normal State Nb3Sn
Abstract
The superconductor Nb3Sn has a high critical temperature and high critical field, widely used for high-field superconducting magnets. In this work we investigate its microscopic electronic structure with 93Nb nuclear magnetic resonance (NMR). The high-quality Nb3Sn powder sample was studied in both 3.2T and 7T magnetic fields in the temperature range from 1.5K to 300K. From measurement of the spectrum and its theoretical analysis, we find evidence for anisotropy despite its cubic crystal structure. This anisotropy is manifest in alignment of powder grains under certain temperature and field cycling conditions. The Knight shift and spin-lattice relaxation rate, T1-1, were measured in the normal state. Additionally, T1-1 was measured in the superconducting state and compared with BCS theory revealing a weak field dependence, with an energy gap (0)=2.00.08kB Tc at 3.2T and (0)=1.730.08kB Tc at 7T, indicating suppression of the order parameter by magnetic field.
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