The Magnetic structure of NpTGa by neutron scattering

Jonen, Shintaro; Metoki, Naoto   ; Honda, Fuminori; Kaneko, Koji   ; Aoki, Dai*; Yamamoto, Etsuji  ; Haga, Yoshinori   ; Shiokawa, Yoshinobu*; Onuki, Yoshichika

The magnetic structure of antiferromagnetic NpPtGa have been clarified by neutron scattering measurements. For temperature below = 27 K, the NpPtGa exhibits an antiferromagnetic structure with propagation vector q=(0 0 1/2), namely the Np moment of 0.4 is parallel to the 100 direction in the basal plane. The neutron scattering measurements under application of magnetic field parallel to the [100] direction, revealed that the field induced phase transition is due a change of antiferromagnetic domain structure from multi-domain to single-domain state. The most intrigued result in this study is the necessity of high magnetic field above 10T at T = 1 K, observed in the magnetic susceptibility. Similar results was observed in NpRhGa, with magnetic moment is parallel to the basal plane at low temperature. The coexistence of ferroquadrupolar order with antiferromagnetic order in NpRhGa, predicted theoretically, might be the hint to understand this problem.