Dimensional Crossover and Angular Dependent Magnetoresistance of Magnetic Graphite Intercalation Compounds; MCl₂GIC's (M=Cu and Co)

Abstract

In order to consider the dimensionality and the interaction between conduction electrons and localized magnetic moments, angular dependences of the magnetoresistance of magnetic GIC's, stage-1 and stage-2 MCl 2 GIC's (M=Cu and Co) were measured. The c-axis (perpendicular to the graphite layers) resistance of stage-1 CuCl 2 GIC shows a typical angular dependent magnetoresistance oscillation (ADMRO) which is commonly observed in several quasi two-dimensional (2D) electron systems with a periodically-warped cylindrical Fermi surface. This proves a band conduction along the c-axis in spite of extremely large anisotropy in conductivity (ρ c /ρ a = 10 5 ). On the other hand, stage-2 CoCl 2 GIC shows a larger MR for the magnetic field along the c axis than that along the graphitic plane. In addition, ADMRO is absent in this compound. These suggest that the c-axis conduction is governed by incoherent interlayer hoppings. The angular dependence of MR in stage-2 CuCl 2 and stage-1 CoCl 2 GIC's show an intermediate behavior between that of stage-1 CuCl 2 GIC and stage-2 CoCl 2 GIC. The above material-dependence is attributed to the difference in interlayer coupling and suggests a dimensional crossover from a highly anisotropic three-dimensional (3D) system (stage-1 CuCl 2 GIC) to an almost pure 2D system (stage-2 CoCl 2 GIC). The c-axis resistances of stage-1 and stage-2 CoCl 2 GIC's reflect also the magnetic states of Co spins. This phenomenon is explained in terms of a model based on spin-dependent tunneling effect.

Two-channel Kondo lattice model on a ladder studied by the density-matrix renormalization-group method

“…This kind of interaction plays a role in other organic compounds, such as the magnetic graphite intercalation compounds. 17 Motivated by the need to understand how a metalinsulator transition arises from pure exchange interactions between the itinerant and localized electrons, this paper examines a Kondo model with two spin-exchange channels sharing a single conduction band: an on-site s-wave (Fig. 1) and a nearest neighbor d-wave coupling (Fig.…”

Electric and magnetic properties of the stage-2 FeBr2graphite intercalation compound

“…The angular dependence of the magnetoresistance in figure 9 was measured to search for the angular dependent magnetoresistance which was first observed in a quasi-two-dimensional organic conductor [17]. It was observed in the stage-1 and stage-2 CuCl 2 GICs [18]. It occurs with a corrugated or undulating Fermi surface in a two-dimensional conductor.…”

Shubnikov-de Haas oscillations and low temperature electronic structure in FeCl3and CoCl2graphite intercalation compounds

“…Graphite intercalation compounds (GIC's) with magnetic intercalants have been extensively studied because intriguing phenomena are expected, arising from the interaction between the conducting πelectrons in the graphene sheets and the localized magnetic moments [1,2]. Among them, FeCl 3 and CoCl 2 GIC's are reported to show antiferromagnetic transitions at high temperatures (T N ~4 K for stage-1 FeCl 3 GIC and T N ~9 K for stage-1 CoCl 2 GIC).…”