Influence of sidewall damage on thermal stability in quad-CoFeB/MgO interfaces by micromagnetic simulation

The influence of the sidewall damage on the thermal stability factor (delta) of quad-interface magnetic tunnel junctions (quad-MTJs) was investigated through a string method-based micromagnetic simulation. The quad-MTJs consist of a reference layer/MgO-barrier/CoFeB/middleMgO/CoFeB/MgO-cap, which has four CoFeB/MgO interfaces to enhance the interfacial perpendicular magnetic anisotropy for large delta. Experimentally obtained magnetic parameters at room temperature [e.g., saturation magnetization (M-s), stiffness constant (A(s)), interfacial perpendicular magnetic anisotropy constants (K-i), and exchange coupling (J(ex))] in blanket multilayer films of the quad-MTJs were used in micromagnetic simulation. The influence of the sidewall damage on the quad-MTJs, which is difficult to be analyzed in the experimental way, was investigated. The quad-MTJs without damaged layers having relatively higher Ki show the split of the energy barrier into two, resulting in a decrease in delta. When the decrease in magnetic anisotropy energy (E-ani) is more than the increase in the static magnetic energy (E-sta), the antiferromagnetically (AF) coupled state of two free layers is formed at the midpoint to minimize the total energy (E-all). This causes the split of the energy barrier. The sidewall damage plays a role in lowering K-i in each layer, consequently avoiding the formation of the AF state. Note that the value of delta with the sidewall damage, which shows the unified energy barrier, is comparable to non-damaged delta, which shows the split of the energy barrier; these quad-MTJs have the same volume of free layers.(c) 2022 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

Automated summary

The influence of sidewall damage on the thermal stability factor of quad-interface magnetic tunnel junctions is investigated through micromagnetic simulation. Sidewall damage causes a split in the energy barrier, resulting in decreased thermal stability.