COERCIVITY MECHANISM AND MICROSTRUCTURE OF (CO/PT) MULTILAYERS

The coercivity mechanism of (Co/Pt) multilayers with high Hc and high squareness fabricated by sputtering is mainly due to the wall-pinning rather than the nucleation process. In order to estimate the size of a wall-pinning site, a study of the temperature dependence of the coercivity, perpendicular magnetic anisotropy, and saturation magnetization for multilayers fabricated under various substrate conditions has been carried out. The size r(o) of the pinning sites of about 4A was obtained for the multilayer film deposited onto an etched SiN(x) film. The size r(o) increases with less interface-sharpness, confirmed by X-ray low angle diffraction. This implies that the pinning site is closely related to the interfacial region. The result is compared to the case of Tb26(FeCo)74 films in which case the size is found to be about 60A - 250A.