Nanoscopic processes of Current Induced Switching in thin tunnel junctions

TL;DR

This paper investigates current-induced resistance switching in magnetic tunnel junctions, attributing the effect to nanostructural ionic electromigration and demonstrating its dependence on structural and magnetic factors at room temperature.

Contribution

It provides a detailed analysis of the nanostructural mechanisms behind CIS in magnetic tunnel junctions, including energy barriers and ionic migration pathways, with experimental validation.

Findings

CIS causes a 6.9% resistance change at room temperature.

Ionic electromigration involves two energy barriers, 0.13 eV and 0.85 eV.

An intermediate resistance state arises from combined magnetic and structural effects.

Abstract

In magnetic nanostructures one usually uses a magnetic field to commute between two resistance (R) states. A less common but technologically more interesting alternative to achieve R-switching is to use an electrical current, preferably of low intensity. Such Current Induced Switching (CIS) was recently observed in thin magnetic tunnel junctions, and attributed to electromigration of atoms into/out of the insulator. Here we study the Current Induced Switching, electrical resistance, and magnetoresistance of thin MnIr/CoFe/AlO$_x$/CoFe tunnel junctions. The CIS effect at room temperature amounts to 6.9% R-change between the high and low states and is attributed to nanostructural rearrangements of metallic ions in the electrode/barrier interfaces. After switching to the low R-state some electro-migrated ions return to their initial sites through two different energy channels. A low (high) energy barrier of $\sim$0.13 eV ($\sim$0.85 eV) was estimated. Ionic electromigration then occurs through two microscopic processes associated with different types of ions sites/defects. Measurements under an external magnetic field showed an additional intermediate R-state due to the simultaneous conjugation of the MR (magnetic) and CIS (structural) effects.