Emma Bernard

Alloys of Co(1-x)Rux have recently gained attention due to their concentration-dependent Curie Temperature, TC, near and below room temperature. The magnetic properties of Co(1-x)Rux near TC have proposed applications in electronic and spintronic devices. In this study, polycrystalline Co(1-x)Rux thin films were prepared by varying the concentration of Ru between x=30-45%. Magnetic and transport characterization was then applied to observe how alloy composition affects resistivity, saturation magnetization, and Curie Temperature, TC. Thin films were grown using DC magnetron sputtering on Si3N4 substrates, each capped with 2 nm Al to avoid oxidation. The thickness of each film was measured using x-ray reflectometry. Vibrating sample magnetometry was used to characterize the magnetic properties of the films by measuring field sweeps of magnetization vs. magnetic field at 5 K and magnetization vs. temperature at 50 Oe. As the concentration of Ru increased, it was found that the magnitude of the saturation magnetization and coercive field decreased while in-plane anisotropy was maintained for all samples. It was also determined that TC decreased to below room temperature as the Ru concentration increased. The Van der Pauw method was used to measure resistivity in the thin films from 4.5 K to 275 K. It was determined that the addition of Ru into Co increases the resistivity over all temperatures, as expected for a disordered alloy.