Pristáš Gabriel, Gabáni Slavomír, Hviščová Petra, Dobrovodský Jozef, Albov Dmitry, Lisnichuk Maksym, Onufriienko Oleksandr, Zorych Janina, Lofaj František, Flachbart Karol
Institute of Experimental Physics of the Slovak Academy of Sciences, Watsonova 47, 040 01 Košice, Slovakia.
Institute of Materials Research of the Slovak Academy of Sciences, Watsonova 47, 040 01 Košice, Slovakia.
Materials (Basel). 2025 Aug 8;18(16):3732. doi: 10.3390/ma18163732.
We report about the effect of nitrogen and carbon concentration on the superconducting transition temperature of (NbMoTaW)CN carbonitride films deposited using reactive DC magnetron sputtering. By measuring the temperature dependence of electrical resistance and magnetization of these carbonitrides, with 0.20 ≤ ≤ 1.17 and 0 ≤ ≤ 0.73, we observe a enhancement that occurs especially at high ( ≥ 0.76) carbon concentrations, with the largest = 9.6 K observed in the over-doped fcc crystal structure with = 1.17 and = 0.41. The reason why the largest appears at high C concentrations is probably related to the lower atomic mass of carbon compared to nitrogen and to the increase in the electron-phonon interaction due to different bonding of carbon (compared to nitrogen) to the Nb-Mo-Ta-W metallic sublattice. However, for concentrations where > 0.71 and + > 1.58, two structural phases begin to form. Additionally, the proximity to structural instability may play a role in the observed enhancement. Further measurements in a magnetic field show that the upper critical fields of (NbMoTaW)CN carbonitrides provide / < 2 T/K, which falls within the weak-coupling pair breaking limit.
