Effects of applying high magnetic field and doping SiO on magnetoresistance and magnetic properties of evaporated Co thin films

Application of high magnetic field (HMF) during the film growth and dopant of SiO are used to affect nanostructure of the evaporated Co films with a thickness of about 30 nm. Then, the relationship of magnetoresistance (MR) and magnetic properties with the nanostructure is explored. The results indicate that columnar growth of the Co film become growth of nanoparticles by doping SiO. HMF and SiO could be used to tune the surface particle size and surface morphology. The SiO suppresses the abnormal aggregation of the Co particle on the surface. The HMF accelerates the Co aggregation on the surface of the Co-SiO films. However, both HMF and SiO have no effect on the hcp phase formation of the films. The variations of these nanostructures significantly affect the MR and magnetic properties. The SiO and the HMF make magnetic isotropy of the Co films become anisotropy. Meanwhile, the coercivity increases 95%. However, the SiO dopant decreases the saturation magnetization. The nanoparticle growth makes the Co-SiO films exhibit a special MR phenomenon that the single MR peak becomes several peaks. These results indicate that the combination of the HMF and SiO dopant provides a new method to affect magnetic properties.