High Bias Voltage Effect on Spin-Dependent Conductivity and Shot Noise in Carbon-doped Fe(001)/MgO(001)/Fe(001) Magnetic Tunnel Junctions

TL;DR

This study investigates how high bias voltages affect spin-dependent conductivity and shot noise in epitaxial Fe-C/MgO/Fe magnetic tunnel junctions, revealing insights into tunneling mechanisms and interface effects.

Contribution

It provides new experimental data on high bias effects in epitaxial magnetic tunnel junctions, highlighting the role of interface electronic structure and demonstrating pure spin-dependent tunneling.

Findings

Large tunnel magnetoresistance observed at room and low temperatures.

Multiple sign inversions of magnetoresistance with bias polarity.

Shot noise remains Poissonian, indicating direct tunneling.

Abstract

Low temperature (10K) high voltage bias dynamic conductivity (up to 2.7V) and shot noise (up to 1V) were studied in epitaxial Fe(100)/Fe-C/MgO(100)/Fe(100) magnetic tunnel junctions, as a function of the magnetic state. The junctions show large tunnel magnetoresistance (185% at 300K and 330% at 4K). Multiple sign inversion of the magnetoresistance is observed for bias polarity when the electrons scan the electronic structure of the bottom Fe-C interface. The shot-noise shows a Poissonian character. This demonstrates a pure spin dependent direct tunneling mechanism and validates the high structural quality of the MgO barrier.