発表者
立川　聡（清水研究室）
指導教員
清水　克哉
Title
Pressure-Induced Superconducting State of Europium Metal at Low Temperatures
Abstract

At ambient pressure, Eu is divalent(4f7, J=7/2) and possesses a strong local magnetic moment which suppresses superconductivity. Under high pressure, it is expected that Eu will become trivalent(4f6, J=0) and a weak Van Vleck paramagnet. It is a good candidate for superconductivity, in analogy with Am(5f6, J=0) metal which superconducts at 0.79 K. We present ac susceptibility and electrical resistivity measurements on Eu metal for temperatures 1.5-297 K to pressures as high as 142GPa. At approximately 80 GPa Eu becomes superconducting at Tc=1.8 K. Tc increases linearly with pressure to 2.75K at 142 GPa. Eu metal thus becomes the 53rd known elemental superconductor in the periodic table.

タイトル
低温におけるユウロピウムの圧力誘起超伝導
概要

　常圧ではEuは２価であり、強い局在磁気モーメントを持っている。それゆえ超伝導にはならない。高圧下ではEuは３価で、弱いバンブレック常磁性体になると予想される。Euに類似したAmは0.79 Kで超伝導となることから、高圧下のEuは超伝導になることが期待される。ここにEuの交流磁化率測定と電気抵抗測定の結果を示す。測定した温度範囲は1.5 Kから297 K　、圧力範囲は142 GPaまでである。約80 GPaでEuは超伝導となりTcは1.8 Kであった。Tcは圧力とともに単調に上昇し、142 GPaで2.75 Kに達した。ここにEuは、超伝導
を示すと分かった53番目の単体元素になった。

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