Interlayer coupling in ultra-thin L10-FePt/MgO/[Co/Pd]30 magnetic tunnel junctions

Perpendicular magnetic anisotropy L1₀-FePt/MgO/[Co/Pd]₃₀ magnetic tunnel junctions (MTJs) with ultra-thin L1₀-FePt layer of thickness 1 to 4 nm were fabricated and studied. The ultra-thin L1₀-FePt behaved as the free layer while the thicker and harder [Co/Pd]₃₀ behaved as the fixed layer. The interlayer coupling within the MTJ with L1₀-FePt layer thickness of 4 nm was attributed mainly to magnetostatic coupling and direct coupling due to pinholes. The magnitude of the interlayer coupling field in the L1₀-FePt/MgO/[Co/Pd]₃₀ MTJ was insignificant compared to the L1₀-FePt based pseudo spin valves reported earlier. There was also no sign of dipolar stray field coupling, owing to the single domain characteristic property of the fixed [Co/Pd]₃₀ layer.