Dependency of tunneling magnetoresistance ratio on Pt seed-layer thickness for double MgO perpendicular magnetic tunneling junction spin-valves with a top Co2Fe6B2 free layer ex-situ annealed at 400 degrees C

Abstract

For the double MgO based perpendicular magnetic tunneling junction (p-MTJ) spin-valves with a top Co2Fe6B2 free layer ex situ annealed at 400 degrees C, the tunneling-magnetoresistance ratio (TMR) strongly depended on the platinum (Pt) seed layer thickness (t(Pt)): it peaked (similar to 134%) at a specific t(Pt) (3.3 nm). The TMR ratio was initially and slightly increased from 113%-134% by the enhancement of the magnetic moment of the Co2Fe6B2 pinned layer when tPt increased from 2.0-3.3 nm, and then rapidly decreased from 134%-38.6% by the degrading face-centered-cubic crystallinity of the MgO tunneling barrier when tPt increased from 3.3-14.3 nm.