Optimizing magneto-ionic performance in structure/composition-engineered ternary nitrides

Magneto-ionics, an emerging approach to manipulate magnetism that relies on voltage-driven ion motion, holds the promise to boost energy efficiency in information technologies such as spintronic devices or future non-von Neumann computing architectures. For this purpose, stability, reversibility, endurance, and ion motion rates need to be synergistically optimized. Among various ions, nitrogen has demonstrated superior magneto-ionic performance compared to classical species such as oxygen or lithium. Here, we show that ternary Co_1-xFe_xN compound exhibits an unprecedented nitrogen magneto-ionic response. Partial substitution of Co by Fe in binary CoN is shown to be favorable in terms of generated magnetization, cyclability and ion motion rates. Specifically, the Co_0.35Fe_0.65N films exhibit an induced saturation magnetization of 1,500 emu/cm³, a magneto-ionic rate of 35.5 emu/(cm³·s) and endurance exceeding 10³ cycles. These values significantly surpass those of other existing nitride and oxide systems. This improvement can be attributed to the larger saturation magnetization of Co_0.35Fe_0.65 compared to individual Co and Fe, the nature and size of structural defects in as-grown films of different composition, and the dissimilar formation energies of Fe and Co with N in the various developed crystallographic structures.