The magnetic properties and microscopic structural of a ferromagnetic semiconductor: Rutile TIO2 single crystals implanted with cobalt ions

Ferromagnetic semiconductors with Curie temperatures higher than room temperature are highly desirable for development of spintronic devices. At room temperature, two crystals of rutile (TiO2) were implanted with Co+ at an energy of 80 keV by using a fluence of 1 × 1017 ions/cm2 and one of the Co-implanted samples was annealed in N2 atmosphere at 900 °C for 30 min. The magnetic properties of Co-implanted samples were measured with superconducting quantum interference device magnetometer (SQUID) at room temperature. Furthermore, the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS) were applied to describe the structural and compositional properties of Co-implanted samples. In our study, the ferromagnetic behavior of Co-implanted samples is detected at room temperature. The saturation magnetization of the un-annealed sample is ~ 6.32 × 10− 4 emu/cm3 and the annealed sample is ~ 6.26 × 10− 5 emu/cm3. Present studies by XRD, XPS and EXAFS indicate that the Co is in a formal oxidation state throughout the implanted region in the annealed sample, and there is sufficient evidence that showed the presence of cobalt single qualitative state for the un-annealed sample. We also attempt to clarify the relation between ferromagnetic behavior and microscopic structure of the Co-implanted samples in this paper.