Strong interlayer exchange coupling and high post-annealing stability in perpendicularly magnetized [Pt/Co]/Ru/[Co/Pt] structures

Strong interlayer exchange coupling (IEC) and high post-annealing stability are demonstrated for perpendicular synthetic ferrimagnets (p-SyFs) with [Pt/Co]6/Ru/[Co/Pt]3 structures. The observed IEC strength was 2.55 ergs/cm2 for a Ru thickness of 0.35 nm, representing the highest value achieved up to date for similar structures. The IEC remained strong even after annealing at 450oC, for the practically important Ru layer thickness of 0.85 nm. The biquadratic IEC, a parameter quantifying the pinhole effects in SyFs, was confirmed by analyzing the experimental results by using the total energy functional, and its strength increased with decreasing the temperature and Ru layer thickness.