The extraordinary Hall effect of Pd/Co multilayers

The magnetoresistivity and Hall resistivity of Pd/Co multilayers have been investigated down to 4.2 K, focusing on the difference between samples with in-plane and perpendicular magnetization. At 4.2 K, a sign change of the extraordinary Hall coefficient as a function of Co thickness is observed at ∼ 2 A . For a Co layer thickness of 2 A, an anomaly is found in the temperature dependence of both resistivity and Hall coefficient near 250 K, suggesting a magnetic phase transition in an alloyed interface region.