Study of magnetic properties on TiO2/Co/TiO2 and Co/TiO2/Co trilayers

In this thesis, a series of TiO2/Co/TiO2 trilayer samples were synthesized by high vacuum based co-sputtering in a RF magnetron system. The samples were grown on the Si(100) substrates. We try to synthesize the Co doped TiO2 dilute magnetic semiconductor structure via thermal treatments under vacuum environment, and study its magnetic property. The results reveal that during thermal treatments in a vacuum environment, the Co grains may form the oxide phase structure, and lose their magnetic properties.

In the second part, we synthesize a series of Co/TiO2/Co trilayer films, with varying the TiO2 spacer layer thickness, and fixing the Co layer thickness to study their interlayer coupling effect. As analyzed from M-H results, the thickness of TiO2 spacer layer (X) strongly influences the ferromagnetic layers to be alignment in parallel or in antiparallel at low temperature. The ESR analysis results also reveal that the peaks of Hr versus angle shift from 90˚ under different TiO2 spacer layer thickness. At X=4~6 nm, it shows the largest shift which is very different from the result of single Co layer. Our experimental results suggest that Co/TiO2/Co may be a candidate for the tunneling magnetoresistance system. However the mechanism of interlayer coupling of Co-layer via TiO2 requires a further investigation.