Thermopower in specular spin valves

Specular spin valves show enhanced giant magnetoresistance due to electron specular reflection at the ferromagnetic (FM)/nano-oxide layer (NOL) interfaces. The two NOLs are formed by the partial oxidation of the FM free and pinned layers. Here we study the thermopower of specular MnIr/CoFe/NOL/CoFe/Cu/CoFe/NOL spin valves (300-10 K). We show that the oxides making the NOL order antiferromagnetically at TN≈150  K. This magnetic ordering induces a large change in the magneto-thermopower (ΔS /S under a magnetic field) as T decreases below TN, and also on the temperature derivative of the electrical resistivity. At low temperatures a quadratic dependence is observed in S(T), likely due to excitation of spin waves.