  We propose versatile materials based on the Ruderman-Kittel-Kasuya-Yosida
(RKKY) interaction in a zigzag silicene nanoribbon (ZSNR) on half filling in
the presence of an out-of-plane electric field. We show that the topological
phase transition in the band dispersion of ZSNR can be probed by using the RKKY
interaction. We find that, due to the zero-energy edge states of the ZSNR, the
exchange coupling is significantly enhanced when the impurities are located on
the zigzag edges, and also explore that the strength of the interaction in the
topological insulator phase is much greater than that when the system is in the
band insulator region. We present a model to investigate the phase of a system
of two magnetic impurities located on the edge of the ZSNR and find that three
different magnetic phases, spiral, ferromagnetic, and anti-ferromagnetic, are
possible for different values of the electric field. This electrical tunability
of the magnetic phases in silicene can be explored by using current
experimental techniques and can be of interest in the field of spintronics.
