The Conductivity and Magnetic Properties of Zinc Oxide Thin Films Doped with Cobalt

The magnetic properties, temperature dependences of the resistivity, Hall constant, and magnetoresistance of epitaxial zinc oxide films doped with cobalt are studied. The ferromagnetism of the films is observed at room temperature. The conduction and magnetoresistance of the films are attributed to transport of electrons in the conduction band at high temperatures and to hopping transport at low temperatures. With increasing concentration of cobalt dopants, the resistivity of the films increases and the concentration of electrons decreases. This is due to the increase in the ionization energy of donor states because of the increase in the energy of exchange interaction between electrons at donor states and electrons of the d shell of cobalt ions.