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The magneto‐ionic modulation of the Dzyaloshinskii–Moriya interaction (DMI) and the perpendicular magnetic anisotropy (PMA), in W/CoFeB/HfO2 stacks annealed at different temperatures and for varying annealing times, are presented in this work. A large modulation of PMA and DMI is observed in the systems annealed at 390 and 350 °C, whereas no response to voltage is observed in the as‐grown samples. A strong DMI is only observed in the samples annealed at 390 °C for 1 h, while PMA is present for all annealing times at temperatures of 390 and 350 °C. Magnetic properties including domain wall velocity improve drastically with increasing the annealing temperature and time, while the magneto‐ionic reversibility is increasingly compromised. The changes in PMA and DMI induced by the gate voltages in the samples annealed at 390 °C are permanent, while partial reversibility is only observed for the samples annealed at 350 °C for short times. This dependence of reversibility on post‐grown annealing has been associated to the influence of crystallization on ion mobility. These results show that a compromise between the enhancement of the magnetic properties and the magneto‐ionic performance could be needed in systems requiring annealing to develop PMA and DMI.

This study reports the effects of post-growth He+ irradiation on the magneto-elastic properties of a Ni/Fe multi-layered stack. The progressive intermixing caused by He+ irradiation at the interfaces of the multilayer allows us to tune the saturation magnetostriction value with increasing He+ fluences and even to induce a reversal of the sign of the magnetostrictive effect. Additionally, the critical fluence at which the absolute value of the magnetostriction is dramatically reduced is identified. Therefore, insensitivity to strain of the magnetic stack is nearly reached, as required for many applications. All the above-mentioned effects are attributed to the combination of the negative saturation magnetostriction of sputtered Ni and Fe layers and the positive magnetostriction of the Ni xFe1− x alloy at the intermixed interfaces, whose contribution is gradually increased with irradiation. Importantly, the irradiation does not alter the layer polycrystalline structure, confirming that post-growth He+ ion irradiation is an excellent tool to tune the magneto-elastic properties of multilayer samples. An alternative class of spintronic devices can be envisioned with a material treatment able to arbitrary change the magnetostriction with ion-induced “magnetic patterning.”