Nano-Oxide-Layer-Induced Magnetic Properties of Ir-Mn-Based Spin-Valve Field Sensors

We report modification of the magnetic properties of Ir-Mn-based bottom spin-valve devices after insertion of a thin Fe-based nano-oxide layer (NOL). A sheet film with layer sequence Si/Ta/Pt/Ir
₂₀
Mn
₈₀
/Co/Ru/Co/FeO
_x
/Co/Cu/Co/ Ni
₈₀
Fe
₂₀
/Ta was grown to fabricate the devices. Magnetization, magneto-transport, angle-dependent resistance, and Fe L
_3,2
-edge X-ray absorption spectroscopy were performed on the sheet film and microfabricated devices. The sheet film and devices had in-plane orthogonal interlayer coupling between the Co layers across the NOL. The sensing capability of the devices was tested and it appears that the NOL affected the free layer and hence the sensing direction of the devices. However, stray fields originating from the reference layer may also influence the free layer. With careful optimization of the NOL and layer structure, the devices may be used as two-axis field sensors after a relatively simple, single-step annealing process.