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 Tn2 = 33 K, respectively. A-type antiferromagnetic structure with the propagation vector q→ = [0 0 1/2] has been revealed below Tn1. 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 Tn2 < T < Tn1 and T < Tn2, respectively. The magnetic moment exhibits a remarkable jump at Tn2, 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.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)