Angular variation of oblique Hanle effect in CoFe/SiO2/Si and CoFe/Ta/SiO2/Si tunnel contacts

Abstract

Oblique Hanle effect (OHE) with magnetic field applied at an oblique angle θ (0 ≤ θ ≤ 180°) was systematically investigated using the 3-terminal (3T) geometry with CoFe/SiO2/Si tunnel contacts. Clear Hanle-like signals with asymmetric voltage dependence are obtained for all angles. It is found that the asymptotic value of the OHE uniquely depends on the angle θ and its angular variation can be fitted well with both functions of cos2θ and 1 1 - α γ 2 cos 2 θ as predicted from spin injection and impurity-assisted magnetoresistance models, respectively. In addition, no Hanle signal is observed in tunnel junctions with spin-unpolarized CoFe/Ta/SiO2/Si structure, which is also understandable by both models. The experimental data in this study demonstrate clearly that further study should be still done to uncover the underlying physics of the Hanle-like signal in 3T tunnel contacts. © 2016 AIP Publishing LLC.