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Non-magnetic to magnetic transition under high pressure in narrow-gap semiconductor $$beta$$-US$$_2$$

狭いバンドギャップを持つ半導体$$beta$$-US$$_2$$の圧力誘起非磁性-磁性転移

立岩 尚之  ; 芳賀 芳範 ; 酒井 宏典  ; 池田 修悟*; 松田 達磨; 山本 悦嗣 ; 大貫 惇睦*

Tateiwa, Naoyuki; Haga, Yoshinori; Sakai, Hironori; Ikeda, Shugo*; Matsuda, Tatsuma; Yamamoto, Etsuji; Onuki, Yoshichika*

ウランカルコゲナイド化合物$$beta$$-US$$_2$$の高圧下磁化測定を行った。この物質は常圧では磁気転移を示さない。過去の電気抵抗測定から2GPa以上で圧力誘起相が存在することが示唆される。本研究では高圧下磁化測定から強磁性的相転移が1GPa以上で現れることが確認され、圧力相図が決定された。$$beta$$-US$$_2$$のウラン5f電子の結晶場基底状態はsinglet stateであることを考慮すると、希土類プラセオジム化合物Pr$$_3$$Tlなどで観測される"induced-magnetic phase"が$$beta$$-US$$_2$$の圧力下で誘起されたことが示唆される。理論モデルを用いた解析結果を報告する。

We have measured the magnetization of an uranium chalcogenide compound $$beta$$-US$$_2$$ under high pressure by piston cylinder and indenter type cells up to 2.42 GPa in a commercial SQUID magnetometer. The compound is a narrow-gap semiconductor that does not order magnetically down to 0.3 K at 1 bar. In this study, it was found that a ferromagnetic state is induced above 1 GPa. The pressure phase diagram were obtained. The values of the spontaneous magnetic moment at 0 K are less than 0.1 $${mu}_{rm B}/{rm U}$$, suggesting that the pressure-induced phase is a very weak ferromagnetic state. Considering the CEF singlet ground state in $$beta$$-US$$_2$$, it is suggest that the ferromagnetic state is an "induced-magnetic phase" often observed in some praseodymium compounds such as Pr$$_3$$Tl. The experimental results are discussed in terms of the mean field theory.

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パーセンタイル:21.57

分野:Physics, Multidisciplinary

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