Thin Film Synthesis, Structural Analysis, and Magnetic Properties of Novel Ternary Transition Metal Nitride MnCoN2

Recent high-throughput computational searches have predicted many novel ternary nitride compounds providing new opportunities for materials discovery in under explored phase spaces. Nevertheless, there are hardly any predictions and/or syntheses that incorporate only transition metals into new ternary nitrides. Here, we report on the synthesis, structure, and properties of MnCoN₂, a new ternary nitride material comprising only transition metals and N. We find that crystalline MnCoN₂ can be stabilized over its competing binaries, and over a tendency of this system to become amorphous, by controlling growth temperature within a narrow window slightly above ambient condition. We find that single-phase MnCoN₂ thin films form in a cation-disordered rocksalt crystal structure, which is supported by ab-initio calculations. X-ray photoelectron spectroscopy analysis suggests that MnCoN₂ is sensitive to oxygen through various oxides and hydroxides binding to cobalt on the surface. X-ray absorption spectroscopy is used to verify that Mn³⁺ and Co³⁺ cations exist in an octahedrally-coordinated environment, which is distinct from a combination of CoN and MnN binaries and in agreement with the rocksalt-based crystal structure prediction. Magnetic measurements suggest that MnCoN₂ has a canted antiferromagnetic ground state below 10 K. We extract a Weiss temperature of θ = -49.7 K, highlighting the antiferromagnetic correlations in MnCoN₂.