Süperiletken FeTe1-xSex (x=0.1-0.4) Tek Kristalleri İçinTe/Se Konsantrasyon Değişimi ve O2 Tavlama İşleminin Süperiletkenlik Özelliklerine Etkisi

Öz

Bu çalışmada Süperiletken FeTe1-xSex (x=0.1-0.4) tek kristaller örnekleri self-flux yöntemiyle başarılı bir şekilde üretilerek Te/Se konsantrasyon değişimi ile O2 tavlama işleminin sistemin süperiletkenlik özelliklerine etkisi ayrı ayrı incelenmiştir. FeTe alaşımı aslında süperiletken olmayıp ~70K’ de antiferromanyetik faz dönüşümüne uğradığı ve Te’ün Se ile kısmi yer değiştirmesi sonucunda da manyetik faz baskılanarak süperiletken fazın ortaya çıktığı bilinmektedir. Bu çalışma kapsamında FeTe1-xSex sistemde Te konsantrasyonundaki artışın süperiletkenlik parametrelerinde (Tc, Hc2, Hirr) ciddi düşüşlere sebep olduğu görülmüştür ve FeTe1-xSex’in x konsantrasyonuna bağlı faz diyagramı bu çalışma kapsamında bir kez daha doğrulanmıştır. O2 ile tavlama işlemi FeTe1-xSex (x=0.1-0.4) sisteminin süperiletkenlik parametrelerinde belirgin bir iyileşmeyi ortaya koymakla birlikte en şaşırtıcı sonuç Hirr hesaplamalarında karşımıza çıkmaktadır. Hirr değerleri Collective Pinning Theory (CPT) ve M-T sonuçları kullanılarak hesaplanmış ve 0Hirr(T)-T(K) eğrileri elde edilmiştir. Te konsantrasyonundaki artış O2 ile tavlama işlemine bağlı olarak 0Hirr(T)-T(K) eğrilerinde vorteks sıvı faz bölgesinin daraldığını ve vorteks cam davranışının etkin olduğu göstermiştir. Bu da daha güçlü vorteks çivileme merkezlerine dolayısıyla da manyetik dayanıma işaret etmektedir. Tc’deki azalmaya rağmen Hirr değerlerindeki artış Fe-bazlı bu sistemlerin düşük sıcaklık uygulamalarında daha avantajlı olacağını ortaya koymaktadır.

Anahtar Kelimeler

• Fe-kalkojenit
• O2 tavlama
• süperiletkenlik.

Destekleyen Kurum

TÜBİTAK

Proje Numarası

115F278

Etik Beyan

Bu çalışma, özgün bir çalışma olup, “FeSe-TABANLI YENİ NESİL SÜPERİLETKEN ALAŞIMLARIN TEK KRİSTAL FORMDA ÜRETİMİ, KARAKTERİZASYONU VE MÜHENDİSLİK UYGULAMALARI" başlıklı doktora tezimden türetilmiş olup 115F278 No’lu TÜBİTAK 1002 Hızlı destek programı kapsamında desteklenmiştir. Tüm deneysel aşamalar, analiz, hesaplama ve yorumlar tarafımca ve doktora tez danışmanım Prof. Dr. M. Eyyuphan YAKINCI danışmanlığında gerçekleştirilmiştir.

Teşekkür

Bu çalışma, 115F278 No' lu TÜBİTAK 1002_Hızlı Destek projesi kapsamında gerçekleştirilmiş olup, desteklerinden dolayı TÜBİTAK' a teşekkür ederiz.

Effect of Te/Se Concentration Change and O2 Annealing Process on Superconductivity Properties of Superconducting FeTe1-xSex (x=0.1-0.4) Single Crystals

Öz

In this study, superconducting FeTe1-xSex (x=0.1-0.4) single crystal samples were successfully produced by the self-flux method, and the effects of Te/Se concentration changes and O2 annealing on the superconducting properties of the system were investigated separately. It is known that the FeTe alloy is not actually superconducting but undergoes an antiferromagnetic phase transformation at ~70 K. The partial replacement of Te by Se suppresses the magnetic phase, resulting in the superconducting phase. In this study, it was observed that increasing the Te concentration in the FeTe1-xSex system causes significant decreases in the superconductivity parameters (Tc, Hc2, Hirr). The phase diagram of FeTe1-xSex, which depends on x concentration, was further confirmed in this study. While the O2 annealing process reveals a significant improvement in the superconductivity parameters of the FeTe1-xSex (x=0.1-0.4) system, the most surprising result is found in the Hirr calculations. Hirr values were calculated using Collective Pinning Theory (CPT) and M-T results, and 0Hirr(T)-T(K) curves were obtained. The increase in Te concentration, due to the O2 annealing process, indicated that the vortex liquid phase region narrowed in the 0Hirr(T)-T(K) curves and that vortex glass behavior became more prevalent. This indicates stronger vortex pinning centers and, consequently, magnetic strength. The increase in Hirr values, despite the decrease in Tc, suggests that these Fe-based systems will be more advantageous in low-temperature applications.

Anahtar Kelimeler

• Fe-chalcogenide
• O2 annealing
• superconductivity

Proje Numarası

115F278

Kaynakça

1. Kamihara, Y., Hiramatsu, H., Hirano, M., Kawamura, R., Yanagi, H., Kamiya, T., & Hosono, H. (2006). Iron-based layered superconductor: LaOFeP. Journal of the American Chemical Society, 128, 10012.
2. Kamihara, Y., Watanabe, T., Hirano, M., & Hosono, H. (2008). Iron-based layered superconductor La(O1−xFx)FeAs (x = 0.05–0.12) with Tc = 26 K. Journal of the American Chemical Society, 130, 3296.
3. Ren, Z. A., Lu, W., Yang, J., Yi, W., Shen, X. L., Li, Z. C., … Zhou, F. (2008). Superconductivity at 55 K in iron-based F-doped layered quaternary compound Sm[O1−xFx]FeAs. Chinese Physics Letters, 25, 2215.
4. Hosono, H., & Kuroki, K. (2015). Iron-based superconductors: Current status of materials and pairing mechanism. Physica C, 514, 399–422.
5. Singh, D. J., & Du, M. H. (2008). Density functional study of LaFeAsO1−xFx: A low carrier density superconductor near itinerant magnetism. Physical Review Letters, 100, 237003.
6. Subedi, A., Zhang, L., Singh, D. J., & Du, M. H. (2008). Density functional study of FeS, FeSe, and FeTe: Electronic structure, magnetism, phonons, and superconductivity. Physical Review B, 78, 134514.
7. Ishibashi, S., Terakura, K., & Hosono, H. (2008). A possible ground state and its electronic structure of a mother material (LaOFeAs) of new superconductors. Journal of the Physical Society of Japan, 77, 053709.
8. Mazin, I. I., Singh, D. J., Johannes, M. D., & Du, M. H. (2008). Unconventional superconductivity with a sign reversal in the order parameter of LaFeAsO1−xFx. Physical Review Letters, 101, 057003.

9. Kuroki, K., Onari, S., Arita, R., Usui, H., Tanaka, Y., Kontani, H., & Aoki, H. (2008). Unconventional pairing originating from the disconnected Fermi surfaces of superconducting LaFeAsO1−xFx. Physical Review Letters, 101, 087004.
10. Yanagi, Y., Yamakawa, Y., & Ono, Y. (2010). Two types of s-wave pairing due to magnetic and orbital fluctuations in the two-dimensional 16-band d–p model for iron-based superconductors. Physical Review B, 81, 054518.
11. Kontani, H., & Onari, S. (2010). Orbital-fluctuation-mediated superconductivity in iron pnictides: Analysis of the five-orbital Hubbard–Holstein model. Physical Review Letters, 104, 157001.
12. Hou, Q., Sun, L., Sun, Y., & Shi, Z. (2023). Review of single crystal synthesis of 11 iron-based superconductors. Materials, 16(14), 4895. doi:10.3390/ma16144895
13. Ozabaci, M. (2023). The superconductivity and structural properties in FeSe0.5Te0.5 with Sb and Sm additions. Journal of Superconductivity and Novel Magnetism, 36, 445–453. doi:10.1007/s10948-023-06505-8
14. Zhang, J., Hänisch, J., Yang, X. S., Zhao, K., & Zhao, Y. (2023). Effect of carbon doping on magnetic flux pinning and superconducting performance in FeSe0.5Te0.5 single crystals. Superconductor Science and Technology, 36, 025008. doi:10.1088/1361-6668/acadb5
15. Shi, K., Zhang, M., Han, Y., Zhao, Y., Wang, Z., Ling, L., … Wang, Z. (2025). Upper critical field and critical current density of Zn and Mn substituted FeSe0.4Te0.6 single crystals. Superconductor Science and Technology, 38, 055023. doi:10.1088/1361-6668/add427
16. Onar, K., Özçelik, B., Güler, N. K., Okazaki, H., Takeya, H., Takano, Y., & Yakinci, M. E. (2016). Enhanced physical properties of single crystal Fe0.99Te0.63Se0.37 prepared by self-flux synthesis method. Journal of Alloys and Compounds, 683, 164–170.
17. Yakinci, K., & Çiçek, Ö. (2026). Improved transport and magnetic properties of MWCNT-substituted Fe-chalcogenide system. Journal of Materials Science: Materials in Electronics, 37, 179. doi:10.1007/s10854-026-16566-9
18. Farisoğulları, D., Güler, N. K., & Yakıncı, K. (2018). The cooling rate effect on structure and flux pinning force of FeTeSe single crystal deposited by self-flux method. Journal of Materials Science: Materials in Electronics, 29, 6477–6483.
19. Kawasaki, Y., Deguchi, K., Demura, S., Watanabe, T., Okazaki, H., Ozaki, T., … Takano, Y. (2012). Phase diagram and oxygen annealing effect of FeTe1−xSex iron-based superconductor. Solid State Communications, 152, 1135–1138.
20. Mizuguchi, Y., Deguchi, K., Tsuda, S., Yamaguchi, T., & Takano, Y. (2010). Evolution of superconductivity by oxygen annealing in FeTe0.8S0.2. Europhysics Letters, 90, 57002.
21. Mizuguchi, Y., Deguchi, K., Kawasaki, Y., Ozaki, T., Nagao, M., Tsuda, S., … Takano, Y. (2011). Superconductivity in oxygen-annealed FeTe1−xSx single crystal. Journal of Applied Physics, 109, 013914.
22. Onar, K. (2017). FeSe-tabanlı yeni nesil süperiletken alaşımların tek kristal formda üretimi, karakterizasyonu ve mühendislik uygulamaları (Doctoral dissertation). İnönü Üniversitesi, Fen Bilimleri Enstitüsü.
23. Hu, T. T., Xie, Y. X., Zhao, K., et al. (2026). The regulation of superconducting properties of Fe(Se, Te) crystal by oxygen doping. Journal of Materials Science, 61, 5311–5323. doi:10.1007/s10853-026-12188-y
24. Luo, S., Wu, Y., Wen, Z., et al. (2022). The crystal structure and superconducting property of (Li0.8Fe0.2)OHFeSe1−xTex. Journal of Superconductivity and Novel Magnetism, 35, 2319–2325. doi:10.1007/s10948-022-06256-y
25. Yakinci, K. (2022). Study on the field-dependent activation energy, U(H,T), upper critical field, Hc2(0), and irreversibility field, μ0Hirr, properties of superconducting single-crystal Ag-added Fe(Se, Te) alloys. Journal of Superconductivity and Novel Magnetism, 35, 2709–2724.
26. Zhang, J., Yang, X. S., Zhao, K., et al. (2022). The effect of grinding condition on superconducting properties for iron chalcogenide Fe(SeTe) crystals. Journal of Materials Science, 57, 9323–9333. doi:10.1007/s10853-022-07263-z
27. Meng, M., Song, D., Xu, Z., Liu, S., Sun, W., Zhang, X., … Zhao, Y. (2025). Structural, superconducting and magnetic properties of oxygen-annealed Fe1+yTe thin films. Advanced Physics Research, e00158. doi:10.1002/apxr.202500158
28. Yakinci, K., Turkoglu, F., Koseoglu, H., et al. (2022). Influences of Pb substitution on microstructure, electrical transport, and mechanical properties of single-crystal FeTe0.5Se0.5 superconductors. Journal of Superconductivity and Novel Magnetism, 35, 2247–2257.
29. Onar, K., & Yakinci, M. E. (2015). Solid state synthesis and characterization of bulk β-FeSe superconductors. Journal of Alloys and Compounds, 620, 210–216.
30. Wen, Z., Xiao, Y., Jia, T., Li, Y., Wu, Y., Li, S., … Zhao, Y. (2024). Flux creep and flux pinning behavior in Cu-doped FeSe0.4Te0.6 single crystals. Physics Letters A, 514–515, 129626. doi:10.1016/j.physleta.2024.129626
31. Zhang, Y., Wang, T., Wang, Z., et al. (2022). Effects of Te- and Fe-doping on the superconducting properties in FeySe1−xTex thin films. Scientific Reports, 12, 391. doi:10.1038/s41598-021-04403-4
32. Ovchenkov, Y. A., Chareev, D. A., Presnov, D. E., et al. (2023). Crossover in low-temperature ground state of Fe(Se,Te) compounds. Journal of Superconductivity and Novel Magnetism, 36, 183–188. doi:10.1007/s10948-022-06437-9
33. Miglani, S. K., & Varma, G. D. (2024). Enhancement of superconducting properties of grown FeTe0.65Se0.35 single crystals through air annealing. Physica Scripta, 99, 125928. doi:10.1088/1402-4896/ad8691
34. Zhao, J., & Wang, Z. (2022). Effect of K-doping on the superconducting properties of FeSe0.5Te0.5 single crystals. Journal of Alloys and Compounds, 917, 165358. doi:10.1016/j.jallcom.2022.165358
35. Chauhan, H., Kumar, R., & Varma, G. D. (2022). Study of anisotropy in the superconducting properties of FeTe0.55Se0.45 single crystal grown by the self-flux method. Superconductor Science and Technology, 35, 045003. doi:10.1088/1361-6668/ac504d
36. Zhang, J., Luo, Y., Hänisch, J., Feng, Y., Yang, X. S., Li, D., … Zhao, Y. (2024). Study of vortex glass-liquid transition and superconducting properties of single-crystalline boron-doped FeSe0.5Te0.5. Journal of Alloys and Compounds, 999, 174908. doi:10.1016/j.jallcom.2024.174908
37. Galluzzi, A., Buchkov, K., Nazarova, E., Leo, A., Grimaldi, G., Pace, S., & Polichetti, M. (2020). Silver doping effects on irreversibility field and pinning energy of a FeSe iron-based superconductor. Journal of Physics: Conference Series, 1548, 012024.
38. Çiçek, Ö., & Yakinci, K. (2022). Structural, magneto-resistivity and magnetization investigations of Y(Ba1−xMgx)2Cu3O7−δ superconducting system. Acta Physica Polonica A, 142(4).