| Summary: | 碩士 === 國立中央大學 === 機械工程研究所 === 87 === Bilayer films of NiO/Ni67Fe17Mo16 were fabricated by sputtering method. The effect of thickness of NiO and NiFeMo on the exchange biasing field (He) and coercive field (Hc) were studied. The results indicate that both the He and Hc decrease with increasing the thickness of NiO(≧30nm), and the He also decreases with increasing the thickness of NiFeMo.
Surface roughness of the NiO layer of the bilayer films was measured using an atomic force microscope(AFM). Mean surface roughness(Ra) was calculated to express the surface roughness. The value of Ra decreases with increasing the thickness of the NiO layer, due to an increase of the NiO columnar grain size but a decrease of its grain number. The increase of Ra on the oxide layer decreases the magnetic domain size, thus increasing the He. In the mean time, this increase in Ra induces additional magnetostatic coupling, or dipole interaction in the bilayer films, and results in an increase of Hc. Obviously, Ra plays an important role on the He and Hc of the NiO/NiFeMo bilayer films.
Through this investigation, a bilayer system of NiO50nm/ NiFeMo10nm films with optimum He and Hc was obtained. This system indicates the values of He at 35.43 Oe and Hc at 4.02 Oe, with a ratio of He/Hc at 8.81 It is very satisfactory for fabrication of a spin-valve magnetoresistance.
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