Magnetism and superconductivity in the new family of actinide compounds; AnPdAl

新しいアクチノイド化合物AnPdAlにおける磁性と超伝導

芳賀 芳範   ; 本間 佳哉*; 青木 大*; 池田 修悟*; 松田 達磨; 立岩 尚之   ; 山本 悦嗣  ; 中村 彰夫; 中島 健次  ; 荒井 康夫; 本多 史憲*; 摂待 力生*; 大貫 惇睦

Haga, Yoshinori; Homma, Yoshiya*; Aoki, Dai*; Ikeda, Shugo*; Matsuda, Tatsuma; Tateiwa, Naoyuki; Yamamoto, Etsuji; Nakamura, Akio; Nakajima, Kenji; Arai, Yasuo; Honda, Fuminori*; Settai, Rikio*; Onuki, Yoshichika

It is now well recognized that 5f electrons in actinide show a variety of intriguing physical properties such as heavy fermions, various magnetic and multipolar orderings and exotic superconductivity. Particularly, superconductivity in transuranium compounds are characterized by rather higher transition temperature compared to uranium- or rare-earth-based superconductor, as well as the existence of localized-like 5f paramagnetic moments following Curie-Weiss law. Among them, NpPdAl is the first neptunium-based heavy fermion superconductor. Detailed investigations of the magnetic and thermal properties around the upper critical field have been performed. It is shown that the large anisotropic paramagnetic moment as well as electronic specific heat existing in the normal state vanish in the superconducting state, indicating a spin-singlet pairing.