Nuclear Magnetic Resonance Investigation of Superconducting and Normal State Nb₃Sn

2023/11/01 by Gan Zhai, Zhai, Gan, W. P. Halperin +13
Engineering · Materials Science · Physics and Astronomy · #Superconducting Materials and Applications #Magnetic Properties of Alloys #Physics of Superconductivity and Magnetism

paper · pdf · doi:10.48550/arxiv.2311.00841

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 Δ(0)=2.0±0.08k_B T_c at 3.2T and Δ(0)=1.73±0.08k_B T_c at 7T, indicating suppression of the order parameter by magnetic field.

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