Magnetoresistance of ZnO and SnO$_{2}$ diluted magnetic oxide thin films

Robust ferromagnetism (FM) at room temperature (RT) in semiconductor materials is critical to the development of spintronic devices making use of both charge and spin of electrons. In this work, magnetotransport techniques were used to study the electronic and magnetic properties of pulsed laser-deposited ZnO and SnO$_{2}$ diluted magnetic semiconductor films on sapphire substrates. Results from thin films with high structural quality showed both semiconductor and ferromagnetic characteristics. Magnetization measurements of Co-doped ZnO showed clear hysteretic behavior indicative of ferromagnetic films even at room temperature. Measurements of resistance versus temperature and magnetic field showed consistency with semiconductor characteristics. All samples were n-type with magnetoresistance (MR) behavior being strongly dependent on carrier concentration.. The presence of magnetic ions significantly affects the scattering of the conduction electrons in cobalt-doped samples resulting in different MR behavior from undoped samples. Correlation of transport characteristics with magnetization will be discussed in the context of carrier-mediated ferromagnetism in diluted magnetic semiconductors.