NMR-STUDY OF BOROCARBIDE SUPERCONDUCTOR Y(NI1-XCOX)(2)B2C

In B-11 NMR experiments, 1/T-1 in the normal state decreases with incr easing Co concentration. These results suggest the decrease of the den sity of states for B at E(F) by the Co substitution at the Ni site rat her than the suppression of AF spin fluctuations of Ni. In Co-59 NMR e xperiments, T-1(-1) decreases exponentially as exp(-Delta/k(B)T(c)) wi th further decrease of T with no appreciable enhancement just below T- c. The ratio 2 Delta/k(B)T(c) was estimated to be about 3 down to 0.5 T-c, which is close to the BCS value of 3.5.