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

TL;DR

This study reports the successful synthesis and characterization of a novel ternary transition metal nitride, MnCoN2, revealing its structure, magnetic properties, and stability, thus expanding the known materials in this class.

Contribution

We demonstrate the synthesis of a new ternary nitride MnCoN2 with a rocksalt structure, supported by computational and experimental analysis, filling a gap in transition metal nitride research.

Findings

MnCoN2 can be stabilized in thin film form at controlled temperatures.

The material exhibits a canted antiferromagnetic ground state below 10 K.

Ab-initio calculations support the rocksalt crystal structure prediction.

Abstract

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 MnCoN$_2$, a new ternary nitride material comprising only transition metals and N. We find that crystalline MnCoN$_2$ 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 MnCoN$_2$ thin films form in a cation-disordered rocksalt crystal structure, which is supported by ab-initio calculations. X-ray photoelectron spectroscopy analysis suggests that MnCoN$_2$ is sensitive to oxygen through various oxides and hydroxides binding to cobalt on the surface. X-ray absorption spectroscopy is used to verify that Mn$^{3+}$ and Co$^{3+}$ 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 MnCoN$_2$ has a canted antiferromagnetic ground state below 10 K. We extract a Weiss temperature of $\theta$ = -49.7 K, highlighting the antiferromagnetic correlations in MnCoN$_2$.