Low frequency noise due to magnetic inhomogeneities in submicron FeCoB/MgO/FeCoB magnetic tunnel junctions

TL;DR

This study investigates low frequency noise caused by magnetic inhomogeneities in submicron FeCoB/MgO/FeCoB magnetic tunnel junctions at room temperature, revealing two types of random telegraph noise linked to magnetic domain walls.

Contribution

It uncovers the presence of two distinct RTN phenomena related to magnetic inhomogeneities in different states and sizes of the junctions, highlighting the role of spin torque at low current densities.

Findings

RTN1 observed in smaller junctions, possibly due to stray field induced MI/DWs.

RTN2 observed in larger junctions, with asymmetry indicating spin torque effects.

Low current densities (<5x10^5 A/cm2) influence magnetic domain wall dynamics.

Abstract

We report on room temperature low frequency noise due to magnetic inhomogeneities/domain walls (MI/DWs) in elliptic submicron FeCoB/MgO/FeCoB magnetic tunnel junctions with an area between 0.0245 and 0.0675{\mu}m2. In the smaller area junctions we found an unexpected random telegraph noise (RTN1), deeply in the parallel state, possibly due to stray field induced MI/DWs in the hard layer. The second noise source (RTN2) is observed in the antiparallel state for the largest junctions. Strong asymmetry of RTN2 and of related resistance steps with current indicate spin torque acting on the MI/DWs in the soft layer at current densities below 5x10^5 A/cm2.