Thermopower in specular spin valves

Abstract

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 T N ≈ 150 K. This magnetic ordering induces a large change in the magneto-thermopower ( Δ S / S under a magnetic field) as T decreases below T N , 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.