Stability of Mn2RuxGa-based Multilayer Stacks.

Perpendicular heterostructures based on a ferrimagnetic Mn2RuxGa (MRG) layer and a ferromagnetic CoPt multilayer were examined to understand the effects of different spacer layers (V, Mo, Hf, HfOx and TiN) on the interfaces with the magnetic electrodes, especially after annealing at 350 C. Loss of perpendicular anisotropy in MRG is strongly correlated with a reduction in the substrate-induced tetragonality due to relaxation of the crystal structure. Hf and Mo are able to stabilise the crystal lattice by filling defects that would be removed during annealing, maintaining the strain in the crystal. The reduction in squareness of the MRG hysteresis loop measured by anomalous Hall effect is <10 %, making it useful in active devices. The solubility of both Hf and Mo in MRG is a source of additional valence electrons, which results in an increase in compensation temperature Tcomp . Furthermore, a (1 1 0) texture in the perpendicular Co/Pt free layer promoted by a Mo spacer layer is the only one that retains its perpendicular anisotropy on annealing.