We studied structural, optical and magnetic properties of high-quality 5 and 15% Co-doped ZnO films grown by plasma-assisted molecular beam epitaxy (MBE) on (0001)-sapphire substrates. Magnetic force microscopy (MFM) and magnetic measurements with SQUID magnetometer show clear ferromagnetic behavior of the films up to room temperature whereas they are antiferromagnetic below 200 K approximately. Temperature dependence of the carrier mobility was determined using Raman line shape analysis of the longitudinal-optical-phonon-plasmon coupled modes. It shows that the microscopic mechanism for ferromagnetic ordering is coupling mediated by free electrons between spins of Co atoms. These results bring insight into a subtle interplay between charge carriers and magnetism in MBE-grown Zn(1-x)CoxO films.
@article{arxiv.1103.4463,
title = {Ferromagnetism in Co-doped ZnO films grown by molecular beam epitaxy: magnetic, electrical and microstructural studies},
author = {V. V. Strelchuk and K. A. Avramenko and V. P. Bryksa and P. M. Lytvyn and M. Ya. Valakh and V. O. Pashchenko and O. M. Bludov and C. Deparis and C. Morhain and P. Tronc},
journal= {arXiv preprint arXiv:1103.4463},
year = {2011}
}