Tunnel Magnetoresistance Enhancement for Pt-Added Magnetic Tunnel Junctions

We study tunnel magnetoresistance (TMR) effects in (CoFe)100-x–Ptx/Al–O/(CoFe)100-x–Ptx (x=0, 7, 21, 32) magnetic tunnel junctions (MTJs) as a function of Pt content. Enhancement of TMR is observed for Pt-added MTJs (x=7, 21) at 5 K and for Pt-added MTJs (x=7) at 300 K in comparison to the reference MTJs (x=0). Very large TMRs of 81% at 5 K and 58% at 300 K are obtained in Pt-added MTJs. Effective barrier height, derived from current-voltage curves fitted to Simmons' model, increases with the Pt content, which can in turn contribute to the increase of TMR values in Pt-added MTJs. Moreover, decay of TMR at elevated annealing temperatures up to 370°C is suppressed by increasing Pt content in magnetic electrodes.