Determination of the Potential Barrier at the Metal/Oxide Interface in a Specular Spin Valve Structure with Nano-oxide Layers by Using Electron Holography

The local potential distribution in a specular spin valve structure with nano-oxide layers has been mapped by using off-axis electron holography in a field emission gun transmission electron microscope. A potential jump of 3-4V across the metal/oxide interface was detected for the first time. The presence of the potential barrier confirms the formation of the metal/insulator/metal structure, which contributes to increasing mean free path of spin-polarized electrons via the specular reflection of spin-polarized electrons at the metal/oxide interface. It leads to nearly double enhancement of the magnetoresistance ratio from 8% to 15%.