Coercivity mechanism and microstructure of (Co/Pt) multilayers

The coercivity mechanism of (Co/Pt) multilayers with high H/sub c/ 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/sub 0/ of the pinning sites of about 4 AA was obtained for the multilayer film deposited onto an etched SiN/sub x/ film. The size r/sub 0/ increases with less interface-sharpness, which was confirmed by X-ray low angle diffraction. This implies that the pinning site is closely related to the interfacial region. An inhomogeneity near the interface between Co and Pt is believed to play a major role as pinning for a wall motion. This result is compared to the case of Tb/sub 26/(FeCo)/sub 74/ films, where the size is found to be about 60 AA approximately 250 AA.< >