Stable magnetic order and charge induced rotation of magnetization in nano-clusters

Efficient control of magnetic anisotropy and the orientation of magnetization are of central importance for the application of nanoparticles in spintronics. Conventionally, magnetization is controlled directly by an external magnetic field or by an electric field via spin-orbit coupling. Here, we demonstrate a different approach to control magnetization in small clusters. We first show that the low magnetic anisotropy of a Co5 cluster can be substantially enhanced by attaching benzene molecules due to the mixing between p states of C and the d states of Co sites. We then show that the direction of magnetization vector of Co5 sandwiched between two benzene molecules rotates by 90° when an electron is added or removed from the system. An experimental set up to realize such effect is also suggested.