Dependency of tunneling magneto-resistance on Fe insertion-layer thickness in Co2Fe6B2/MgO-based magnetic tunneling junctions

Abstract

For Co2Fe6B2/MgO-based perpendicular magnetic tunneling junctions spin valves with [Co/Pd](n)-synthetic-antiferromagnetic (SyAF) layers, the tunneling-magneto-resistance (TMR) ratio strongly depends on the nanoscale Fe insertion-layer thickness (t(Fe)) between the Co2Fe6B2 pinned layer and MgO tunneling barrier. The TMR ratio rapidly increased as t(Fe) increased up to 0.4 nm by improving the crystalline linearity of a MgO tunneling barrier and by suppressing the diffusion of Pd atoms from a [Co/Pd](n)-SyAF. However, it abruptly decreased by further increasing t(Fe) in transferring interfacial-perpendicular magnetic anisotropy into the IMA characteristic of the Co2Fe6B2 pinned layer. Thus, the TMR ratio peaked at t(Fe) = 0.4 nm: i.e., 120% at 29 Omega mu m(2).