Hidden Spin Scattering Behavior in [Ni1-xCux(tmdt)2] System with Unprecedentedly Strong π-d Interaction

We have measured the electrical resistivity and magnetoresistance of [Ni1-xCux(tmdt)(2)] (x = 0 and x approximate to 0.10) single crystals to investigate the role of the pi-d exchange interaction, J(pi-d), where tmdt stands for trimethylenetetrathiafulvalenedithiolate. At 0 T, the difference in the resistivity between x approximate to 0.10 and x = 0 as a function of temperature, rho(mag)(T), increases logarithmically with decreasing temperature expected for a Kondo alloy. However, it does not show a logarithmic divergence but tends to saturate at a constant value. For H > 0, rho(mag)(T, H) is quite field-dependent, which is very similar to that observed in other Kondo compounds. Assuming that the effect of magnetic field on rho(mag)(T) is attributed to the suppression of the Kondo effect, the Kondo magnetic field H-K similar to 7 T and the Kondo temperature T-K similar to 5 K are found, which is consistent with the previous report on the magnetic susceptibility measurements. The pi-d interaction of J(pi-d) approximate to 30 meV is obtained using the relation k(B)T(K) approximate to E-F expd(-1/vertical bar J(pi-d)vertical bar N(E-F)), where N(E-F) is the density of states at the Fermi energy E-F.