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The rare-earth mononitrides (LnN, Ln a lanthanide) form a mutually epitaxy-compatible series of ferromagnetic semiconductors with promise for mixed superconductor-spintronics.[1] Their varying occupation of 4f states precipitate enormously varied and useful magnetic properties, the topic of intense recent investigation toward those applications.[2,3] Their electrical properties can be controlled independently to their magnetic properties by tuning the deposition conditions to incorporate nitrogen vacancies. The usage of ionized or molecular nitrogen, which catalytically reacts at the surface at ambient temperatures provides capacity for nitrogen-vacancy rich LnN to be formed, and therefore very conductive LnN films to be made. [4,5] Here Raman spectroscopy on the LnN and the identification of Ln vacancies are discussed via the identification of a high-frequency cation-centered symmetric N breathing mode.
This research compares the Raman peak mode frequencies and breathing modes about cation vacancies computed using density functional theory (DFT) for a variety of LnN: LaN, GdN, ErN, and LuN. We find excellent agreement with the measured LnN cation vacancy breathing mode frequencies when using a combined Hubbard U parameter correction approach applied to the 4f and 2p states of Ln and N, respectively. In conclusion, the capacity to incorporate and identify the presence of cation vacancies in a family of compounds otherwise restricted to n-type transport opens the door for p-type material discovery in the rare-earth mononitrides.
References:
[1] Natali, F. et al. (2013), Progress in Materials Science 58, 1316.
[2] Pal, A. et al. (2013), Advanced Materials 25, 5581.
[3] Pot, C. et al. (2023), Applied Physics Letters 123, 202401.
[4] Ullstad, F. et al. (2019), ACS Omega 4, 5950.
[5] Chan J. et al. (2020), Applied Surface Science 632, 157550.
| Field of Condensed Matter | Energy and Functional Materials |
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