First principles modeling of tunnel magnetoresistance of Fe/MgO/Fe trilayers

TL;DR

This study uses first principles density functional theory and non-equilibrium Green's functions to analyze the quantum transport and TMR behavior of Fe/MgO/Fe trilayers under bias, aligning well with experimental data.

Contribution

It provides a detailed first-principles analysis of the bias-dependent TMR in Fe/MgO/Fe trilayers, including microscopic insights into scattering states and band structures.

Findings

Large equilibrium TMR ratio stable against atomic variations

TMR decreases monotonically with bias voltage to zero around 1V

Microscopic analysis explains transport properties and TMR behavior

Abstract

By carrying out density functional theory analysis within the Keldysh non-equilibrium Green's functional formalism, we have calculated the nonlinear and non-equilibrium quantum transport properties of Fe/MgO/Fe trilayer structures as a function of external bias voltage. For well relaxed atomic structures of the trilayer, the equilibrium tunnel magnetoresistance ratio (TMR) is found to be very large and also fairly stable against small variations in the atomic structure. As a function of external bias voltage, the TMR reduces monotonically to zero with a voltage scale of about 1V, in agreement with experimental observations. We present understanding of the nonequilibrium transport properties by investigating microscopic details of the scattering states and the Bloch bands of the Fe leads.