Transparent magnetic semiconductors based on ZnO

Transparent magnetic semiconductors have been constructed by introducing transition metals such as Co or V into wurtzite ZnO crystals by a non-equilibrium thin film technique using laser molecular beam epitaxy. Co and V substituted for Zn have a divalent cationic state in the ZnO thin films formed epitaxially on the sapphire substrates. Raman measurements show that the wurtzite crystal structure can be maintained up to 15% and 5% for Co and V substitution, respectively. The results from photoemission spectra also suggest that Co does has not a metal state but a 2+ state. Magnetic circular dichroism (MCD), x-ray MCD, superconducting quantum interference device (SQUID) and nuclear magnetic resonance (NMR) measurements on (Zn, Co)O films indicate ferromagnetic properties with magnetizations of 0.1-0.3 μ B /Co.