Polycrystalline CPP-GMR devices using <001> textured Co2Fe(Ga0.5Ge0.5) Heusler alloy layer and conductive Mg0.5Ti0.5Ox buffer layer

摘要

Current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with Co-based Heusler alloys have recently drawn considerable attention due to their potential application as read sensors for ultrahigh density magnetic recording. With a non-magnetic Ag spacer layer, the resistance change-area product (ΔRA) of epitaxial pseudo spin valves (PSVs) on single crystalline (001) MgO substrates has exceeded 10 mΩ μm by using quaternary ferromagnetic (FM) Heusler alloys such as CoFe(GaGe) (CFGG) and CoFeMnSi (CFMS). From a practical point of view, however, we need to develop CPP-GMR sensors with polycrystalline thin films at relatively low annealing temperatures (<;400°C). Our previous work on <;001> textured polycrystalline CPP-GMR using MgO buffer layer showed favorable device thermal stability and moderate ΔRA of 5.8 mΩ μm at 400°C was obtained. Nevertheless, it is not industrially viable because MgO as an insulator cannot be used for the fabrication of the actual CPP-GMR sensors. In this work, we report the CPP-GMR properties and microstructure of PSV devices using <;001> textured FM Heusler layer CFGG and Ag spacer with a conductive buffer layer MgTiO (MTO) deposited on an chemically-mechanically polished (CMP) Ta/Cu/Ta electrode on thermally oxidized Si substrates. Relatively large ΔRA of 6.6 mΩ μm and desirable interfacial smoothness make it a promising candidate for actual read head design.