Magnetic properties of stage-2 random-mixture graphite intercalation compounds and their bulk intercalants

Abstract

The magnetic properties of stage-2 Co c M 1− c Cl 2 graphite intercalation compounds (GICs) (M = Ni and Mn, 0 ≤ c ≤ 1) and their bulk intercalants, Co c M 1− c Cl 2, have been studied by using d.c. magnetic susceptibility. In stage-2 Co c M 1− c Cl 2 GIC, the adjacent Co c M 1− c Cl 2 layers are separated by two graphite layers. Due to the graphite host effect, demonstrated by decreasing the antiferromagnetic interplanar exchange interaction and island formation in the intercalate layer, the magnetic phase transition of stage-2 Co c M 1− c Cl 2 GIC is very different from that of Co c M 1− c Cl 2. Stage-2 Co c Ni 1− c Cl 2 GIC with 0 ≤ c ≤ 1 and stage-2 Co c Mn 1− c Cl 2 GIC with 0.45 ≤ c ≤ 1 undergo a two-dimensional ferromagnetic phase transition at the critical temperature T c, while their bulk intercalants undergo a three-dimensional antiferromagnetic phase transition at the Néel temperature T N. The magnetic properties of stage-2 GICs are compared with those of their respective bulk intercalants in the light of the graphite host effect. The magnetic properties of stage-2 Co c Mn 1− c Cl 2 GIC and Co c Mn 1− c Cl 2 are also compared with those of stage-2 Co c Mg 1− c Cl 2 GIC and Co c Mg 1− c Cl 2.