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

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
²
by using quaternary ferromagnetic (FM) Heusler alloys such as Co
₂
Fe(Ga
_0.5
Ge
_0.5
) (CFGG) and Co
₂
Fe
_0.4
Mn
_0.6
Si (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
²
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 Mg
_0.5
Ti
_0.5
O
_x
(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
²
and desirable interfacial smoothness make it a promising candidate for actual read head design.