We have fabricated single C60 molecule transistors with ferromagnetic Ni leads (FM-SMTs) by using an electrical break junction method and investigated their magnetotransport. The FM-SMTs exhibited clear gate-dependent hysteretic tunnel magnetoresistance (TMR) and the TMR values reached as large as -80 %. The polarity of the TMR was found to be always negative over the entire bias range studied here. Density functional theory calculations show that hybridization between the Ni substrate states and the C60 molecule orbitals generates anti-ferromagnetic configuration in the local density of states near the Fermi level, which gives a reasonable explanation for the observed negative TMR.
