Pinhole and tunneling conduction channels superimposed in magnetic tunnel junction: results and inferences

TL;DR

This study investigates how ballistic and tunneling conduction channels coexist in magnetic tunnel junctions, revealing that superimposed channels cause magnetoresistance inversion and clarifying the existence of ballistic magnetoresistance.

Contribution

It demonstrates the coexistence of ballistic and tunneling channels in magnetic tunnel junctions and clarifies the origin of ballistic magnetoresistance, resolving previous controversies.

Findings

Magnetoresistance inversion observed over a broad temperature range.

Sign change in tunnel magnetoresistance at higher bias and temperature.

Ballistic magnetoresistance confirmed to exist independently of artifacts.

Abstract

The influence of ballistic channels superimposed on tunneling conduction channels in magnetic tunnel junctions has been studied in a manganese oxide based tunneling device. Inversion of magnetoresistance has been observed in magnetic tunnel junctions with pinhole nanocontacts over a broad temperature range. The tunnel magnetoresistance undergoes a change of sign at higher bias and temperature. This phenomenon is attributed to the parallel conduction channels consisting of spin conserved ballistic transport through the pinhole contact where the transmission probability is close to unity and spin polarized tunneling across the insulating spacer with weak transmittivity. The results seem to resolve a controversy regarding ballistic magnetoresistance in ferromagnetic nanocontacts and establishes that ballistic magnetoresistance do exist even if the previous results are attributed to magnetostriction and magnetostatic force related artifacts.