Dependence of Giant Tunnel Magnetoresistance of Sputtered CoFeB/MgO/CoFeB Magnetic Tunnel Junctions on MgO Barrier Thickness and Annealing Temperatur

TL;DR

This study explores how the giant tunnel magnetoresistance (TMR) in sputtered CoFeB/MgO/CoFeB magnetic tunnel junctions depends on MgO barrier thickness and annealing temperature, revealing high TMR ratios after optimal annealing.

Contribution

It demonstrates the relationship between MgO barrier thickness, annealing temperature, and TMR performance in sputtered magnetic tunnel junctions, highlighting the effects of annealing on crystalline structure and TMR enhancement.

Findings

Resistance-area product increases exponentially with MgO thickness.

Annealing at 375°C induces crystalline structure in the junctions.

TMR ratio reaches 260% at room temperature and 403% at 5 K.

Abstract

We investigated the dependence of giant tunnel magnetoresistance (TMR) on the thickness of an MgO barrier and on the annealing temperature of sputtered CoFeB/MgO/CoFeB magnetic tunnel junctions deposited on SiO2/Si wafers. The resistance-area product exponentially increases with MgO thickness, indicating that the quality of MgO barriers is high in the investigated thickness range of 1.15-2.4 nm. High-resolution transmission electron microscope images show that annealing at 375 C results in the formation of crystalline CoFeB/MgO/CoFeB structures, even though CoFeB electrodes are amorphous in the as-sputtered state. The TMR ratio increases with annealing temperature and is as high as 260% at room temperature and 403% at 5 K.