Ferrimagnets have received renewed attention as a promising platform for spintronic applications. Of particular interest is the Mn4N from the ε-phase of the manganese nitride as an emergent rare-earth-free spintronic material due to its perpendicular magnetic anisotropy, small saturation magnetization, high thermal stability, and large domain wall velocity. We have achieved high-quality (001)-ordered Mn4N thin film by sputtering Mn onto η-phase Mn3N2 seed layers on Si substrates. As the deposited Mn thickness varies, nitrogen ion migration across the Mn3N2/Mn layers leads to a continuous evolution of the layers to Mn3N2/Mn2N/Mn4N, Mn2N/Mn4N, and eventually Mn4N alone. The ferrimagnetic Mn4N, indeed, exhibits perpendicular magnetic anisotropy and forms via a nucleation-and-growth mechanism. The nitrogen ion migration is also manifested in a significant exchange bias, up to 0.3 T at 5 K, due to the interactions between ferrimagnetic Mn4N and antiferromagnetic Mn3N2 and Mn2N. These results demonstrate a promising all-nitride magneto-ionic platform with remarkable tunability for device applications.
Ionically driven synthesis and exchange bias in Mn4N/MnNx heterostructures
Zhijie Chen, Christopher J. Jensen, Chen Liu, Xixiang Zhang, Kai Liu; Ionically driven synthesis and exchange bias in Mn4N/MnNx heterostructures. Appl. Phys. Lett. 21 August 2023; 123 (8): 082403. https://doi.org/10.1063/5.0165895
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