75As-NMR studies on Ba(Fe1-xNix)2As2 single crystals

75As nuclear magnetic resonance (NMR) were measured for Ba(Fe1-xNix)2As2 single crystals with x = 0.05 and x = 0.1 under 0 GPa and 1.5 GPa, respectively. For the optimal doped sample with x = 0.05, the superconducting transition temperature Tc is strongly suppressed from 18 K to 5 K, while for the over-doped sample with x = 0.1, it is turned from the superconducting ground state to a disordered paramagnetic state under 1.5 GPa. Our experimental results show that the antiferromagnetic spin fuctuations are suppressed as well as Tc. The experimental results can be explained with the two-band model. As a result, the electronic band is downward shifted with increase of pressure and the electrons become the dominant carriers in the system.