Effects of overlayer capping and lattice strain on perpendicular magnetic anisotropy of TM|FePt|MgO heterostructures

Magnetic tunnel junctions (MTJs) with ferromagnetic electrodes possessing the strong perpendicular magnetocrystalline anisotropy (PMA) are of great interest as they have a potential for realizing next-generation high-density non-volatile memory and logic chips. To date, it is an urgent and critical issue to continuously promote the PMAs through feasible modifications such as the substitution of ferromagnetic layers as well as the overlayer coating on them. Here, we perform the relativistic first principles calculations of TM|L1(0)-FePt|MgO sandwich systems, and demonstrate that the changes in PMAs by capping TM layers are always giant and positive, e.g., PMA of Fe|FePt|MgO, the largest one among all our studied systems, is about 2 times larger than that of FePt|MgO. The interfacial PMAs at TM|FePt and FePt|MgO interfaces are extracted to be 3.31~9.40 meV and 3.32 meV, respectively, which are at least 3 times larger than 0.93 meV/ML of interior FePt layer. We illustratively verify that PMAs of TM|FePt|MgO can be turned in a large range by varying the TM layer and in-plane strain. Our results and model analyses provide useful insights for how these magnetic quantities are linked, and pave a way for the promotion of PMAs of FePt-based heterostructures via contact with TM overlayers.