Crystal orientation dependence of current-perpendicular-to-plane giant magnetoresistance of pseudo spin-valves with epitaxial Co₂Fe(Ge _0.5Ga_0.5) Heusler alloy layers

The magnetoresistive (MR) properties of Co₂Fe(Ge _0.5Ga_0.5) (CFGG) Heusler alloy-based current- perpendicular-to-plane giant magnetoresistance pseudo-spin-valves (PSVs) are investigated. The PSV films are epitaxially grown on a sapphire (112̄0) substrate with an Ag or Cu spacer layer, and their magnetoresistive properties are compared with those of PSV grown on MgO(001) substrates. For substrates with an Ag spacer, the PSV with the (001)[110]_CFGG//(001)[010] _Ag interface grown on MgO(001) exhibits a higher MR output compared with the (110)[001]_CFGG//(111)[11̄0]_Ag interface grown on sapphire (112̄0). In contrast, a higher MR output is obtained using a Cu spacer with the (110)[001]_CFGG//(111)[11̄0] _Cu interface. These results demonstrate that the MR outputs depend upon the crystal orientation at the interface, and that interfaces with a small misfit tend to exhibit a larger MR output. This indicates the influence of crystal orientation as well as lattice mismatch upon the interfacial spin scattering asymmetry.