Enhancement of Extraordinary Hall Effect in Pt/CoFe Multilayers With a Small Amount of Fe Doped Into Pt Layers

The extraordinary Hall effect (EHE) is investigated for the Pt/CoFe multilayers with a small amount of Fe doped into Pt layers. It is found that, through varying CoFe layer thickness and/or the content of Fe in Pt layers, high sensitivity linear EHE can be achieved in the Fe doped Pt/CoFe multilayers at room temperature. Most remarkably, both the saturation Hall resistivity and the Hall angle are significantly enhanced upon adding a small amount of Fe into Pt layers, reaching 1.2 μΩ·cm and 1.8%, respectively. The EHE sensor based on the Fe doped Pt/CoFe multilayers has the field sensitivity over 400 V/A T, which is twice as large as that of the pure Pt/CoFe multilayers and much higher than the best value ever achieved in Pt-based ferromagnetic alloy thin films. The present results suggest that, due to the large Hall effect and the adjustable interface anisotropy, the Fe doped Pt/CoFe multilayer film should be a potential candidate for magnetic field sensor application.