Nuclear magnetic resonance study in Nb₃Sn

The superconducting compound Nb₃Sn is widely used for applications where high critical temperature and high critical field are important. However, there has as yet not been any comprehensive investigation of its properties using nuclear magnetic resonance. We have performed ⁹³Nb NMR on high-quality Nb₃Sn powder in 3.2 T and 7 T magnetic fields, with a temperature range from 1.5 K to 300 K. The spectrum measurements indicate that there exists magnetic anisotropy although the sample has a cubic crystal structure. This anisotropy leads to alignment of powder grains under specific temperature and field protocols. We measured the Knight shift and spin-lattice relaxation rate T₁^-1 in the normal state, and the latter in the superconducting state. From this data we obtained the field dependent energy gap and compared with BCS theory.