Four-point bend adhesion measurements of copper and permalloy systems

The four-point bend split-beam method is used to quantitatively determine the interfacial fracture resistance and crack velocity as a function of mechanical energy release rate of the weakest interface in a thin film stack. Various interfaces of importance to magnetic storage devices are studied, including copper or nickel–iron (permalloy) on silicon oxynitride with additional adhesion promoters. The dynamics and kinetics of the four-point bend test are fully elucidated. A model for environmentally-controlled crack growth previously applied to bulk ceramics is used here as a model for interfacial crack growth and is found to fit the kinetic data.