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<p>This study investigates, for the first time in the literature, how substituting MWCNTs affects the structural, microstructural, electrical, and magnetic properties of single-crystal FeTe<sub>0.5</sub>Se<sub>0.5</sub> alloy. The MWCNTs were integrated into Fe sites in single crystalline Fe<sub>1₋x</sub>(MWCNT)<sub>x</sub>Te<sub>0.5</sub>Se<sub>0.5</sub> (x = 0%–5%). One of our key findings is that MWCNTs dissolve well in the FeSeTe matrix up to a 4% substitution level, but beyond 3%, they appear as impurity phases within the structure. The electrical transport properties improved with increasing substitution, reaching their peak at 3%, but declined with further substitution, transforming the structure into a fully non-conductive form. The best electrical performance was obtained for the x = 3% sample with <i>T</i><sub>on</sub> and <i>T</i><sub>c</sub> values of 16.5&#xa0;K and 15.6&#xa0;K, respectively. This corresponds to a 1.7&#xa0;K improvement in <i>T</i><sub>c</sub> value compared to the x = 0% sample. The <i>J</i><sub>c</sub> value was calculated as 1.4 × 10<sup>5</sup> A/cm<sup>2</sup> for the x = 0% and 1.1 × 10<sup>6</sup> A/cm<sup>2</sup> for the x = 3% sample, indicating a significant improvement of ~ 9.5 times. Similar improvement was also observed for the pinning force property, with <i>F</i><sub>p</sub> = 2.15 × 10<sup>6</sup> N/m<sup>3</sup> for the x = 0% and <i>F</i><sub>p</sub> = 4.91 × 10<sup>7</sup> N/m<sup>3</sup> for the x = 3% sample, indicating an improvement of more than 20 times. The<i> H</i><sub>c2</sub>(0) values increased with higher MWCNTs content, with the maximum <i>H</i><sub>c2</sub>(0) calculated as 78.1&#xa0;T for the x = 3% sample. A notable decrease in U<sub>0</sub>/<i>k</i><sub>B</sub> occurs as both the substitution rate and the applied field increase. This decline supports the idea that the thermally activated dissipation mechanism and independent vortex mobility are at play.</p>

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Improved transport and magnetic properties of MWCNT-substituted Fe-chalcogenide system

  • 期刊论文

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  • 发表日期：

    2026年1月11日

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  • K. Yakinci,
  • Ö. Çiçek

摘要

This study investigates, for the first time in the literature, how substituting MWCNTs affects the structural, microstructural, electrical, and magnetic properties of single-crystal FeTe0.5Se0.5 alloy. The MWCNTs were integrated into Fe sites in single crystalline Fe1₋x(MWCNT)xTe0.5Se0.5 (x = 0%–5%). One of our key findings is that MWCNTs dissolve well in the FeSeTe matrix up to a 4% substitution level, but beyond 3%, they appear as impurity phases within the structure. The electrical transport properties improved with increasing substitution, reaching their peak at 3%, but declined with further substitution, transforming the structure into a fully non-conductive form. The best electrical performance was obtained for the x = 3% sample with Ton and Tc values of 16.5 K and 15.6 K, respectively. This corresponds to a 1.7 K improvement in Tc value compared to the x = 0% sample. The Jc value was calculated as 1.4 × 105 A/cm2 for the x = 0% and 1.1 × 106 A/cm2 for the x = 3% sample, indicating a significant improvement of ~ 9.5 times. Similar improvement was also observed for the pinning force property, with Fp = 2.15 × 106 N/m3 for the x = 0% and Fp = 4.91 × 107 N/m3 for the x = 3% sample, indicating an improvement of more than 20 times. The Hc2(0) values increased with higher MWCNTs content, with the maximum Hc2(0) calculated as 78.1 T for the x = 3% sample. A notable decrease in U0/kB occurs as both the substitution rate and the applied field increase. This decline supports the idea that the thermally activated dissipation mechanism and independent vortex mobility are at play.