Magnetic Properties of Cobalt-Ion-Implanted SiO2 Thin Films

Abstract

The physical properties of magnetic-ion-implanted nanoparticle systems depend on the preparation and processing conditions, and this fact may be utilized to design a material system with desired properties. For this purpose, the magnetic properties of various Co implanted SiO2 thin films were systematically studied. SiO2 thin films were grown on Pt/Ti/SiO2/Si (100) substrates by using thermal evaporation, and Co ions of different energies (40 and 100 keV) and doses (1, 3, 7, 10, 13 X 10(16) ion/cm(2)) were implanted into the films. Magnetization, ferromagnetic resonance (FMR), and scanning electron microscope (SEM) measurements for the films were carried out either as-prepared or after annealing at 600 degrees C. While 40 keV Co ions were spread under the surface of the films and the internal field did not change significantly with dose, 100 keV ions went deeper into the films, and their internal field changed with dose. Post-annealing further induced Co nanoparticles with different shapes and sizes in the films. In general, magnetization measurements showed that the freezing temperature of the films shifted to higher temperatures with increasing dose. FMR absorption spectra were recorded as a function of magnetic field at room temperature and the effective magnetization was calculated from the FMR data. We found that the effective magnetization increased with dose while the magnetic anisotropy decreased with dose.