The Study Of Giant Magnetoresistance (GMR) Spin-Valve Pinning Layer

PtMn has practically been used as anti-ferromagnetic layer to pin ferromagnetic layers because of its large exchange bias, high blocking temperature and excellent thermal stability. On the other hand, PtMn films deposited by magnetron sputtering without substrate heating require a relatively high temperature post-deposition annealing in magnetic field to induce a unidirectional exchange field Hes. That is to say, in order to achieve transformation from nonmagnetic fcc phase structure to fct state with strong anti-ferromagnetism, a high post-deposition temperature (about 260 C) anneal must be performed. But long time anneal will cause thermal degradation the whole spin-valve because of interlayer diffusion. So to shorten annealing temperature and time is a vital issue.In this study we focused on the pinning structure, and prepared [Pt/Mn]n multilayer by dc magnetron sputtering system instead of using co-sputtering, by which we wish to find a way to reduce the critical annealing temperature and shorten the annealing time. By using X-ray diffraction(XRD) and Vibrating-Sample magnetometer(VSM) we find about 260 C is the critical temperature to complete the transformation of ordered anti-ferromagnetic fct phase. We also find that the pinning phenomenon gradually disappear with thicker single layer of the [Pt/Mn]n films, and firstly prepared permalloy before the deposition of [Pt/Mn]n multiplayer more easily form anti-ferromagnetic structure than another caseo Maybe this is a good way to shorten the annealing time.