MgO barrier-perpendicular magnetic tunnel junctions with CoFe/Pd multilayers and ferromagnetic insertion layers

TL;DR

This study investigates how ferromagnetic layer insertion affects the tunnel magnetoresistance in MgO-based magnetic tunnel junctions with CoFe/Pd multilayers, revealing optimal annealing conditions for high TMR ratios.

Contribution

It demonstrates the impact of ferromagnetic layer insertion and annealing processes on TMR performance in MgO-based MTJs with CoFe/Pd multilayers.

Findings

TMR ratio reaches 67% at 200°C annealing.

TMR ratio degrades above 250°C due to crystallization effects.

In-situ annealing at 350°C yields 78% TMR after post-annealing.

Abstract

The authors studied an effect of ferromagnetic (Co20Fe60B20 or Fe) layer insertion on tunnel magnetoresistance (TMR) properties of MgO-barrier magnetic tunnel junctions (MTJs) with CoFe/Pd multilayer electrodes. TMR ratio in MTJs with CoFeB/MgO/Fe stack reached 67% at an-nealing temperature (Ta) of 200 degree C and then decreased rapidly at Ta over 250 degree C. The degradation of the TMR ratio may be related to crystallization of CoFe(B) into fcc(111) or bcc(011) texture result-ing from diffusion of B into Pd layers. MTJs which were in-situ annealed at 350oC just after depo-siting bottom CoFe/Pd multilayer showed TMR ratio of 78% by post annealing at Ta =200 degree C.