▎ 摘　　要

Motivated by the recent experimental and theoretical effects for the electronic-correlation and magnetism in the bulk ABC-trilayer graphene (ABC-TLG), we use the tight-binding and the Hubbard model to investigate the magnetism and magnetic phase transitions of the finite-width ABC-TLG nanoribbon. Under the ferromagnetic exchange field, a series of phase transitions and a quantized magnetic hysteresis cycle among various magnetic orders are observed. We employed a simplified Ising model derived from the molecular orbitals of edge-state to quantitatively explain these magnetic phase transitions. We also observe some demagnetization phase transitions under the in-plane electric field. The two-factor competition and multi-step demagnetization mechanisms are proposed to analyze these electric-field induced phase transitions. The temperature effects on the magnetization phase transition and the electric-field-induced demagnetization are also investigated. We consider this work provides insights into a theoretical guidance and possible applications to the future nano-spintronics.