  Electric field effect on magnetism is an appealing technique for manipulating
the magnetization at a low cost of energy. Here, we show that the local
magnetization of the ultra-thin Co film can be switched by just applying a gate
electric field without an assist of any external magnetic field or current
flow. The local magnetization switching is explained by the nucleation and
annihilation of the magnetic domain through the domain wall motion induced by
the electric field. Our results lead to external field free and ultra-low
energy spintronic applications.
