(Zn,Co)O alloyed magnetic semiconductor: giant magnetization and experimental determination of band structure

Magnetic semiconductor exhibits both ferromagnetism and semiconductor properties. Since the magnetic dopants tend to aggregate in, the thermo-dynamical miscibility of transition metals in semiconductors is in fact extremely low (generally <15\%, in diluted region). The miscibility of transition metals exceeding diluted region is challenge for material science and future spintronic applications. In this paper, we have been grown (Zn,Co)O thin films by oxygen plasma-assisted molecular beam epitaxy. The Co context in these films can be up to 45\%, which we defined as alloyed magnetic semiconductor (AMS). The measurements of RHEED, XRD and in. situ. XPS indicated that (Zn, Co)O films are spinodal decomposition phase with ZnO wurtzite lattice. The saturated magnetization at room temperature was remarkably enhanced with increasing the Co content. It reach 530emu/cm${3}$ at x = 45\% which corresponds to the average magnetic moment 1.6$\mu_{B}$ per Co. The electronic band structure of (Zn,Co)O films were determined by angle resolved photoemission.