J. Phys. Soc. Jpn. 75S (2006) pp. 41-43  |Previous Article| |Next Article|  |Table of Contents|
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Proc. of 5th Int. Symposium on ASR-WYP-2005 – Advances in the Physics and Chemistry of Actinide Compounds –

A-Type Antiferromagnetic Ordering and the Transition of the 5f Electronic State Accompanied by Unusual Moment Reorientation in NpRhGa₅

Shintaro Jonen¹, Naoto Metoki^1,2, Fuminori Honda¹, Koji Kaneko¹, Etsuji Yamamoto¹, Yoshinori Haga¹, Dai Aoki³, Yoshiya Homma³, Yoshinobu Shiokawa^1,3 and Yoshichika Ōnuki^1,4

Elastic neutron scattering experiments have been carried out in order to reveal the magnetic structure and 5f electronic state of NpRhGa₅. This material exhibits two successive antiferromagnetic transition at T_N1 = 36 K and T_N2 = 33 K, respectively. A-type antiferromagnetic structure with the propagation vector q = [0, 0, 1/2] has been revealed below T_N1. This antiferromagnetic structure is the same as that for NpCoGa₅, UPdGa₅ and UPtGa₅. The identical magnetic structure is reasonably understood from the electronic structure; These iso-electronic compounds have very similar cylindrical fermi surfaces. We found a remarkable change in the moment direction, namely the Np moment is parallel and perpendicular to the c-axis for T_N2 < T < T_N1 and T < T_N2, respectively. The magnetic moment exhibits a remarkable jump at T_N2, indicating that the moment reorientation is associated with the transition of 5f electronic state at T_N2. This electronic transition would be a consequence of the competition of the magnetic and/or quadrupolar interaction between different 5f electronic states. The observed magnetic form factor indicates the dominant contribution of the orbital moment, while the orbital contribution is reduced from the Np³⁺ free ion state. This is consistent with the itinerant character of the 5f electrons in NpRhGa₅, which is revealed by the dHvA experiments and the band calculation study.

URL: http://jpsj.ipap.jp/link?JPSJS/75S/41/
DOI: 10.1143/JPSJS.75S.41

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