Thin-Film Stabilization and Magnetism of η-Carbide Type Iron Nitrides
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| Main Authors: | , , , , , , |
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| Format: | Preprint |
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2026
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| _version_ | 1866910040825266176 |
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| author | Julien, Baptiste Rauf, Abrar Nagle-Cocco, Liam A. V. Smaha, Rebecca W. Sun, Wenhao Zakutayev, Andriy Bauers, Sage R. |
| author_facet | Julien, Baptiste Rauf, Abrar Nagle-Cocco, Liam A. V. Smaha, Rebecca W. Sun, Wenhao Zakutayev, Andriy Bauers, Sage R. |
| contents | Transition-metal nitrides in η-carbide type structures exhibit unusual bonding motifs and proximity to magnetic instabilities. Yet they remain unexplored in thin-film form due to the difficulty of stabilizing nitrogen-poor ternaries among competing phases. Here, we report the thin-film synthesis and phase-stability mapping of the η-nitride systems Fe-W-N and Fe-Mo-N. Amorphous Fe-M-N (M = W, Mo) combinatorial libraries deposited by reactive co-sputtering crystallize upon rapid thermal annealing, enabling systematic identification of synthesis windows as a function of composition and annealing temperature. Using laboratory powder X-ray diffraction and synchrotron grazing incidence wide angle X-ray scattering, we establish that Fe3Mo3N-based η-carbide phases form over a substantially broader compositional and thermal range than W-based compositions, where η structures are stabilized only when the films are Fe-rich. These trends are rationalized using mixed chemical-potential vs. composition phase diagrams that capture the narrow nitrogen chemical-potential stability of η-nitrides. Magnetic measurements reveal that ferromagnetism is induced in Fe-rich Fe3.54Mo2.46N with a small exchange-bias-like response that is absent in Fe3W3N-based compositions, highlighting the sensitivity of magnetic behavior to modest deviations from stoichiometry. This work establishes practical thin-film synthesis routes for η-nitride materials and demonstrates how composition can be tuned to access emergent magnetic phenomena in these complex nitrides. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2602_06236 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Thin-Film Stabilization and Magnetism of η-Carbide Type Iron Nitrides Julien, Baptiste Rauf, Abrar Nagle-Cocco, Liam A. V. Smaha, Rebecca W. Sun, Wenhao Zakutayev, Andriy Bauers, Sage R. Materials Science Transition-metal nitrides in η-carbide type structures exhibit unusual bonding motifs and proximity to magnetic instabilities. Yet they remain unexplored in thin-film form due to the difficulty of stabilizing nitrogen-poor ternaries among competing phases. Here, we report the thin-film synthesis and phase-stability mapping of the η-nitride systems Fe-W-N and Fe-Mo-N. Amorphous Fe-M-N (M = W, Mo) combinatorial libraries deposited by reactive co-sputtering crystallize upon rapid thermal annealing, enabling systematic identification of synthesis windows as a function of composition and annealing temperature. Using laboratory powder X-ray diffraction and synchrotron grazing incidence wide angle X-ray scattering, we establish that Fe3Mo3N-based η-carbide phases form over a substantially broader compositional and thermal range than W-based compositions, where η structures are stabilized only when the films are Fe-rich. These trends are rationalized using mixed chemical-potential vs. composition phase diagrams that capture the narrow nitrogen chemical-potential stability of η-nitrides. Magnetic measurements reveal that ferromagnetism is induced in Fe-rich Fe3.54Mo2.46N with a small exchange-bias-like response that is absent in Fe3W3N-based compositions, highlighting the sensitivity of magnetic behavior to modest deviations from stoichiometry. This work establishes practical thin-film synthesis routes for η-nitride materials and demonstrates how composition can be tuned to access emergent magnetic phenomena in these complex nitrides. |
| title | Thin-Film Stabilization and Magnetism of η-Carbide Type Iron Nitrides |
| topic | Materials Science |
| url | https://arxiv.org/abs/2602.06236 |