Nano particles of iron oxides in SiO2 glass prepared by ion implantation

Quartz (SiO2) glass was implanted with 5-9x1016 57Fe ions/cm² at a substrate temperature of 500°C, and annealed at temperatures between 700 and 950°C. The implanted and annealed plates were characterized by conversion electron Mössbauer spectroscopy (CEMS), and measured by a Kerr effect magnetometer or a vibration sample magnetometer. Kerr effect measurement of as-implanted SiO2 glass showed ferromagnetism at room temperature. CEM spectrum of the as-implanted glass consisted of magnetic relaxation peaks of finely dispersed metallic Fe species, and paramagnetic doublets of Fe3+ and Fe2+ species. The sample heated at 700°C contained large grains of metallic Fe and a lot of oxidation products of Fe2+ species. After oxidation at temperatures higher than 800°C, the samples showed also ferromagnetism, which was attributed mainly to ferromagnetic e-Fe2O3 precipitated in SiO2 matrix. Small amounts of a-Fe2O3 were produced at 950°C. The results suggest that ion implantation and oxidation make a transparent ferromagnetic glass possible.