Optimization of top-pinned perpendicular anisotropy tunnel junctions through Ta insertion

We study the influence of a tantalum spacer layer sandwiched between the FeCoB polarizing section and the Co/Pt high anisotropy section in the reference layers of top-pinned perpendicular magnetic anisotropy magnetic tunnel junctions (MTJ). In addition to Kerr magnetometry, we use ferromagnetic resonance (FMR) to obtain the coupling J through Ta and the anisotropies of all the magnetic parts of our MTJ. This layer-by-layer assignment is allowed by the distinct FMR frequency identities of each subsystem of the MTJ. A high J together with optimal Co/Pt properties is obtained for 4 angstrom of Ta. (C) 2015 The Japan Society of Applied Physics