New type of antiferromagnetic state in stacked nanographite

Abstract

Nanographite systems, where graphene sheets of the orders of the nanometer size are stacked, show novel magnetic properties, such as, spin-glass like behaviors and the change of ESR line widths in the course of gas adsorptions. We theoretically investigate stacking effects in the zigzag nanographite sheets by using a tight binding model with the Hubbard-like onsite interactions. We find a remarkable difference in the magnetic properties between the simple A-A and A-B type stackings. For the simple stacking, there are not magnetic solutions. For the A-B stacking, we find antiferromagnetic solutions for strong onsite repulsions. The local magnetic moments tend to exist at the edge sites in each layer due to the large amplitude of wavefunctions at these sites. We study variations between the A-A and A-B stackings to find that the magnetism between the two stackings experiences the first order phase transition. The effect of the interlayer distance is also discussed.Comment: 12 pages; http://www.etl.go.jp/~harigaya/welcome_E.htm

Mechanism of magnetism in stacked nanographite with open shell electrons

“…The magnetic moment increases as U becomes larger as expected for the increase of the localized characters of electrons. In contrast, the magnetic moment is a weak decreasing function with respect to d. shell electron system is in contrast with that of the closed shell electron system reported in the paper [7]. The present calculation is in qualitative agreement with that of the experiment which reports the decrease of the magnetization in the course of the adsorption of molecules [4,5].…”

“…In the calculations, the finite magnetization develops, as the hopping interactions between layers increase in the case of the A-B stacking [6]. The same conclusion has been obtained when the system is near the A-B stacking and the interlayer distance becomes shorter [7]. The A-B stacking should exist in nanographite systems, because the exotic magnetisms have been observed in recent experiments [1][2][3].…”

“…The same technique (unrestricted Hartree-Fock approximation) used in ref. [6,7,19] is effective for the open shell electronic systems of this paper. The number of unit cells in the stacking direction is 10, and therefore there are 20 layers in the system used for the numerical treatment.…”

Persistence of Edge-State in Stacked Graphene and Nano-Graphene Materials

“…The Pauli susceptibility decreases due to the decrease of the magnetic moment magnitude. We have studied the magnetism of the nanographite using the tight binding model including the interlayer interaction between neighboring nanographene layers [6][7][8]. We have found that open shell nature of each layer might explain the experimental observations.…”

Possible Magnetic States in Buckybowl Molecules

“…The Hubbard model [5][6][7] is applied to π-electrons on the curved molecules. We will discuss that the molecular structure determines the magnetism in the sumanene, while the edge state gives magnetism along the zigzag edge of a part of C 60 .…”