在地球磁場冷卻下對樣品Li0.2FeTe0.6Se0.4做比熱研究

Specific Heat Study of Li0.2FeTe0.6Se0.4 under Earth’s Field Cooling

陳亭羽(TING-YU CHEN)

指導教授 ： 李文新

國立中正大學/理學院/物理學系/碩士(2016年)

摘要

Li0.2FeTe0.6Se0.4 此樣品在外加磁場0.5 Oe下，做 ZFC (Zero Field Cooling) 之磁性量測時，Tc,onset = 11.5 K，可是在外加磁場0.5 Oe之冷卻下，磁性量測在整個溫度區間 (4.6 K ~ 20 K) 並沒有看到明顯的順磁和超導的反磁相變化產生。
比熱可以用來探討塊材超導性質，然而Li0.2FeTe0.5Se0.5在不同外加磁場的ZFC (Zero Field Cooling) 量測下，發現此超導的低臨界磁場Hc1很小~ 0.5 Oe，可是在0.5 Oe FC (Field cooling) 過程所量測到之磁化數據並沒有明顯的相變化，由於鮮少有超導體具有如此小之低臨界磁場Hc1特性，因此我們利用比熱量測來再次檢測此樣品，是否仍有超導性質。
從我們比熱量測的結果顯示，Li0.2FeTe0.6Se0.4 樣品在地球磁場冷卻下，確實沒有看到比熱有超導的相變化現象，在低溫時一般金屬材料的比熱主要是由電子和聲子的貢獻，可以表示成：C = γ T + βT3也可寫成為：C/T = γ + βT2，然後利用C/T vs T2的圖可以算出Li0.2FeTe0.6Se0.4 之電子比熱係數γ = 36.1 mJ/mole‧K2和聲子的比熱係數β = 0.73 mJ/mole‧K4 ，相當於Debye Temperature (ΘD) = 181 ± 5 K。

關鍵字

比熱 ； 超導體

並列摘要

Li0.2FeTe0.6Se0.4 this sample when sur- magnetic field 0.5 Oe, makes ZFC (Zero Field Cooling) the magnetic gauging, Tc = 11.5 K, but cooling of in under the sur- magnetic field 0.5 Oe, the magnetic gauging (4.6 K ~ 20 K) had not seen in the entire temperature sector the obvious paramagnetic and superconductivity counter-magnetism changes the production.
The specific heat may use for to discuss the block material superconductivity nature, however Li0.2FeTe0.5Se0.5 in different sur- magnetic field ZFC (Zero Field Cooling) under the gauging, discovers this superconductivity low threshold field Hc1 very small ~ 0.5 Oe, but (Field cooling) the process gauges in 0.5 Oe FC arrives the magnetization data not to change obviously, because few has the superconductor to have the so small low threshold field Hc1 characteristic, therefore we use the specific heat to gauge examine this sample once more, whether still had the superconductivity nature.
Showed from our specific heat gauging result that, the Li0.2FeTe0.6Se0.4 sample under terrestrial magnetic field cooling, had not seen truly the specific heat has the superconductivity to change the phenomenon, when low temperature the general metal material specific heat mainly is by electronic and the phonon contribution, may express: C = γ T + βT3 also may write is: C/T = γ + βT2, then may figure out Li0.2FeTe0.6Se0.4 electron of specific heat coefficient γ = 36.1 mJ/mole‧K2 and phonon specific heat coefficient β = 0.73 mJ/mole‧K4 using the C/T vs T2 chart, is equal in Debye Temperature (ΘD) = 181 ± 5 K。

並列關鍵字

specific heat ； superconductor

參考文獻

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