Effective magnetic correlations in hole-doped graphene nanoflakes

The magnetic properties of zigzag graphene nanoflakes (ZGNFs) are investigated within the framework of inhomogeneous dynamical mean-field theory. At half-filling and for realistic values of the local interaction, the ZGNF is in a fully compensated antiferromagnetic (AF) state, which is found to be robust against temperature fluctuations. Introducing charge carriers in the AF background drives the ZGNF metallic and stabilizes a magnetic state with a net uncompensated moment at low temperatures. The change in magnetism is ascribed to the delocalization of the doped holes in the proximity of the edges, which mediate ferromagnetic correlations between the localized magnetic moments. Depending on the hole concentration, the magnetic transition may display a pronounced hysteresis over a wide range of temperatures, indicating the coexistence of magnetic states with different symmetries. This suggests the possibility of achieving electrostatic control of the magnetic state of ZGNFs to realize a switchable spintronic device.