Transport properties of magnetic intercalation compounds

The resistivity for stage-1 CoCl₂-GICs decreases with increasing temperature below the Neel temperature T_N = 9.8 K. This anomaly was explained by the formation of a modified Fermi surface which is caused by an extra periodic potential due to the antiferromagnetic ordering along the c-axis below T_N. To understand the mechanism of the anomaly more clearly, the previous theory is extended. An investigation of the a-axis resistivity, ρ{variant}_a, and the c-axis resistivity, ρ{variant}_c, of stage-1 and 2 Co_1-xFe_xCl₂-GICs (x = 0.02 ∼ 0.03) is carried out. T- and H-dependences of ρ{variant}_c for the stage-1 CoCl₂-GIC are essentially the same as those of ρ{variant}_a. A mechanism is proposed to explain the reason why Co_1-xFe_xCl₂-GIC shows a different T-dependence in ρ{variant}_c from that of CoCl₂-GIC. A mechanism for the transfer process across the intercalant layers is presented and the magnitude of the transfer integral J is estimated.