Abstract
Magnetization (M) comes from both the persistent currents and the spin polarization. The spin-B interaction is important in a graphene tubule, because it makes the one-dimensional subband with the divergent density of states capable of crossing the Fermi level (=0 eV). It causes cusps in magnetization and power divergencies in differential susceptibility (), and destroys the periodicity (period =hc/e) of the physical properties. The special structures shown in M and are found to be insensitive to the chirality. The power divergencies in are replaced by the peak structures at low temperature (T). The order of is –; therefore, the peak structures are measurable at T≤1 K. The temperature effect in reducing magnetization is relatively obvious for a larger semiconducting tubule. Moreover, the anomalous temperature effect due to the spin-B interaction exists in all the metallic tubules at the relatively low T. For the doped graphene tubule, M and exhibit more special structures, since both the electronic structure and the finite Fermi level vary with φ simultaneously. The magnetic response is enhanced by the doping, and it is relatively strong for a larger tubule. The magnetism at the small flux is possibly altered from paramagnetism (diamagnetism) to diamagnetism (paramagnetism) by varying the free-carrier density.
- Received 3 April 1995
DOI:https://doi.org/10.1103/PhysRevB.52.8423
©1995 American Physical Society