Extrinsic tunnel Hall effect in CoFeB/MgO/Pt junctions

TL;DR

This paper investigates the nonlinear Hall effect in CoFeB/MgO/Pt tunnel junctions, revealing contributions from known effects and a novel quadratic spin-orbit scattering phenomenon induced by high electric fields.

Contribution

It introduces the observation of a quadratic Hall effect caused by spin-orbit scattering in tunnel junctions, expanding understanding of spin-dependent transport phenomena.

Findings

Linear Hall component includes anomalous and inverse spin-Hall effects.

Quadratic Hall component arises from spin-orbit scattering under high electric fields.

Effect magnitude decreases with increasing platinum thickness due to shunting.

Abstract

The Hall effect that occurs when current flows through a CoFeB/MgO/Pt tunnel junction is investigated. It is shown that the transverse voltage in Pt electrode is nonlinear on a DC voltage applied to the tunnel junction. It has both linear (odd) and quadratic (even) parts. The linear part contains well-known contributions of the anomalous Hall effect in the ferromagnetic electrode, inverse spin-hall effect in platinum and others. The quadratic part is a phenomenon caused by the spin-orbit scattering of electrons in an external electric field induced by a voltage applied to the barrier. This field reaches values of $10^9$ V/m which is close to internal atomic fields. The magnitude of both effects decreases as thickness of Pt electrode is increased due to shunting effects.