Monte Carlo study of magnetization plateaus in a zigzag graphene nanoribbon structure

The Monte Carlo simulation has been applied to discuss the step effect on a zigzag graphene nanoribbon structure in a longitudinal magnetic field. The effects of the singe-ion anisotropies, longitudinal magnetic fields and temperature on the magnetization plateaus have been investigated in detail. Our results show that the number of magnetization plateaus for the system dissatisfy 2S + 1 criterion at low temperatures, originating from not only the competition between the anisotropy and the external magnetic field, but also the contributions of edge effects. It has been found that the single-ion anisotropy plays a significant role in modulating the spin configurations of the zigzag graphene nanoribbon structure. In addition, the effects of single-ion anisotropies and external magnetic fields on the magnetization, the susceptibility, the internal energy and the blocking temperature have been examined.

The graphene nanoribbon system can exhibit rich and interesting magnetization plateau behaviors with different single-ion anisotropies and longitudinal magnetic fields at low temperatures, due to the competition between the single-ion anisotropies, the longitudinal fields as well as the edge effects. It is worthwhile mentioning that most magnetization plateaus of the system may not satisfy the 2S + 1 criterion, originating from the cooperation not only between the homogeneous atoms from the marginal and internal parts, but also between different kinds of atoms.114