▎ 摘　　要

We have investigated, using effective mass approach (EMA), magnetic properties of a one-dimensional electron gas in graphene armchair ribbons when the electrons occupy only the lowest conduction subband. We find that magnetic properties of the one-dimensional electron gas may depend sensitively on the width of the ribbon. For ribbon widths L-x = 3Ma(0), a critical point separates ferromagnetic and paramagnetic states while for L-x = (3M + 1)a(0) paramagnetic state is stable (M is an integer and a(0) is the length of the unit cell). These width-dependent properties are a consequence of eigenstates that have a subtle width-dependent mixture of K and K' states, and can be understood by examining the wavefunction overlap that appears in the expression for the many-body exchange self-energy. Ferromagnetic and paramagnetic states may be used for spintronic purposes. (C) 2012 Elsevier Ltd. All rights reserved.