Compositionally tunable Néel temperature in Mn1−xCoxN: A route to enhance magneto-ionic exchange bias control

To address growing computational demands, energy-efficient hardware technologies such as spintronics and neuromorphic computing have attracted significant interest. In particular, magneto-ionics offers a low-power, non-volatile approach to control magnetic properties, making it particularly suitable for manipulating antiferromagnetic (AFM) materials. In this work, we report magneto-ionic control of exchange bias (EB) in Mn 1− x Co x N/Co with a compositionally tunable Néel temperature, T N . The high T N in MnN (> 650 K) typically necessitates high-temperature annealing, which triggers uncontrolled thermally induced ion-motion effects. Addition of Co to MnN reduces T N , enabling robust EB to be established after field cooling from 400 K, while preserving structural integrity. Importantly, EB can be subsequently tuned by voltage, up to a 30% enhancement observed at 100 K alongside an increase in saturation magnetization (up to ≈ 250 emu cm −3 ). Unlike previous works on similar single-layer nitrides, incorporating an additional ferromagnetic Co layer to form an AFM/ferromagnetic bilayer amplifies the voltage-induced effects. This work highlights the dual role of Co addition to MnN: (i) reducing the thermal requirements for setting EB by lowering T N , and (ii) enhancing electrical control of EB. These results represent a step forward towards the development of low-power voltage-controlled spintronic devices.