Joint perpendicular anisotropy and strong interlayer exchange coupling in systems with thin vanadium spacers

We study the influence of the insertion of a vanadium spacer layer between an FeCoB layer and a [Co/Ni] multilayer in an MgO substrate-based system mimicking the reference system of a perpendicular anisotropy magnetic tunnel junction. The anisotropy of the [Co/Ni] multilayer gradually improves with the vanadium thicknesses t, up to an optimized state for t = 8 angstrom, with little influence of the thermal annealing. The interlayer exchange coupling is ferromagnetic and very strong for t <= 6 angstrom. It can be adjusted by thermal treatment at t = 8 angstrom from no coupling in the as-grown state to more than 2mJ/m(2) after 250 degrees C annealing. For this spacer thickness, the magnetic properties are consistent with the occurrence of a bcc (001) to an fcc (111) crystalline structure transition at the vanadium spacer. The remaining interlayer exchange coupling at t = 8 angstrom is still substantially higher than the one formerly obtained with a Tantalum spacer, which holds promise for further optimization of the reference layers of tunnel junctions meant for magnetic random access memories. 2015 AIP Publishing LLC.