Magnetic origin of phase stability in cubic γ-MoN
Among transition-metal nitrides, the mononitride γ-MoN with a rock-salt structure has drawn particular attention because it has been predicted to possess excellent mechanical and electronic properties, especially the high superconducting temperature around 30 K. However, synthesis of bulk γ-MoNx wit...
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Veröffentlicht in: | Applied physics letters 2018-11, Vol.113 (22) |
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Sprache: | eng |
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Zusammenfassung: | Among transition-metal nitrides, the mononitride γ-MoN with a rock-salt structure has drawn particular attention because it has been predicted to possess excellent mechanical and electronic properties, especially the high superconducting temperature around 30 K. However, synthesis of bulk γ-MoNx with the nitrogen concentration, x, more than 0.5 is still challenging, leading to contradictions on its phase stability and properties. In this work, we formulated a high-pressure synthesis reaction for the formation of single-crystal γ-MoNx with a remarkably high nitrogen concentration value of x ≈ 0.67. This nitride possesses a high asymptotic hardness of ∼24 GPa, which is so far the second hardest among metal nitrides. Impressively, the expected superconductivity is absent in the as-synthesized product. We further performed density functional theory calculations to clarify the structural stability and the absence of superconductivity in stoichiometric γ-MoN. We find that the ground state of γ-MoN is theoretically explored to be a Mott insulator with an antiferromagnetic phase, while a paramagnetic configuration is adopted at the ambient conditions. Such magnetic properties would explain the structural stability and the absence of superconductivity in the as-synthesized γ-MoNx with a high nitrogen concentration. |
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ISSN: | 0003-6951 1077-3118 |
DOI: | 10.1063/1.5048540 |