Electronic property of the c-site doped MgCNi

C-site doped MgCNi₃ compounds, MgC_1-x B _x Ni₃ (x=0.15, 0.20) and MgC _y Ni₃ (y=1.00, 0.80, 0.65), have been investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The binding energies of Ni 2p3/2 and C 1s for undoped MgCNi₃ are 853.173 eV and 283.640 eV, respectively. Interestingly, the binding energy of Ni 2p3/2 is found to shift to a lower value with decreasing C-site occupation in MgC _y Ni₃ samples. The C-site doped by boron could also lead to a slight decrease of the binding energy of Ni 2p3/2. However, the C-site doping has few effects on the binding energy of C 1s. It is suggested that there is charge transfer from Ni- to C-site atom. The hybridism between Ni and C has an important effect on the superconductivity of MgCNi₃.