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by neutron diffractionJonen, Shintaro; Metoki, Naoto; Yamamoto, Etsuji; Homma, Yoshiya*; Aoki, Dai*; Shiokawa, Yoshinobu*; Onuki, Yoshichika
Journal of Alloys and Compounds, 448(1-2), p.84 - 88, 2008/01
Times Cited Count：1 Percentile：12.92(Chemistry, Physical)The magnetic structure of NpPtGa
was investigated by neutron diffraction. NpPtGa exhibits an A-type antiferromagnetic structure with propagation vector 
= (0 0 1/2) below 
= 26 K. The estimated Np magnetic moment is 0.38(5) 
, and it is oriented parallel to the 
100
direction. This small moment would be consistent with the large 
= 123 mJ/(K
mol), indicative of the heavy fermion nature. The field-induced anomaly in the magnetic susceptibility is clarified to be a signature for an antiferromagnetic domain change between multi-domains to single-domain states.
electronic transition in the itinerant antiferromagnet NpRhGa
Jonen, Shintaro; Metoki, Naoto; Honda, Fuminori; Kaneko, Koji; Yamamoto, Etsuji; Haga, Yoshinori; Aoki, Dai*; Homma, Yoshiya*; Shiokawa, Yoshinobu*; Onuki, Yoshichika*
Physical Review B, 74(14), p.144412_1 - 144412_8, 2006/10
Times Cited Count：26 Percentile：71.23(Materials Science, Multidisciplinary)Neutron diffraction experiments have been carried out in a single crystal of NpRhGa in order to reveal the magnetic structure and 5 electronic state of this compound. An antiferromagnetic structure with the propagation vector = (0 0 1/2) appears below 
. We found a remarkable change in the moment direction at 
, namely, the Np moment is parallel to the 
-axis for 
(AF1), but parallel to the 110 direction for 
(AF2). The magnitude of magnetic moment exhibits a discontinuous change at , indicating that the moment reorientation is associated with a change of the 5 electronic state. This transition might be the consequence of the competition between the magnetic and/or quadrupolar interaction in the low-moment and high-moment states. The observed magnetic form factor indicates a dominant contribution from the orbital moment, but the orbital contribution is reduced from the Np free ion state. This is consistent with the itinerant character of the 5 electrons in NpRhGa, which is revealed by dHvA experiments and band structure calculations.
Honda, Fuminori; Metoki, Naoto; Kaneko, Koji; Jonen, Shintaro; Yamamoto, Etsuji; Aoki, Dai*; Homma, Yoshiya*; Haga, Yoshinori; Shiokawa, Yoshinobu*; Onuki, Yoshichika*
Physical Review B, 74(14), p.144413_1 - 144413_12, 2006/10
Times Cited Count：20 Percentile：64.35(Materials Science, Multidisciplinary)Systematic neutron scattering experiments have been carried out in order to reveal the magnetic properties of NpNiGa. We have observed successive ferromagnetic transitions with the magnetic moment parallel to the tetragonal -axis at 
= 30 K and 18 K. We have also observed antiferromagnetic reflections with the propergation vector 
= [1/2 1/2 1/2], coexisting with the ferromagnetic component below 
= 18 K. Spin polarized neutron scattering experiments have revealed that only Np carries a magnetic moment. We conclude that the magnetic moments of Np atoms exhibit simple ferromagnetic ordering for 
, while a canted antiferromagnetic structure appears for . The size of the Np magnetic moment 0.78 
/Np at 3 K have been estimated. The temperature and the magnetic field dependences of these two components have also been quantitatively analyzed. (1) It is quite unusual that the Np total moment increases with the transition from the ferromagnetic to canted antiferromagnetic structure. (2) The metamagnetic transition cannot be explained in terms of a simple spin-flip mechanism with competing interactions and anisotropy. (3) Furthermore, unusual reduction of the Np magnetic moment has been accompanied by the metamagnetic transition. From these three results, we concluded that a remarkable change in the 5
electronic state was associated with the transition at and the metamagnetic transition between the ferromagnetic low-moment state and the canted antiferromagnetic high-moment state. An important role in the 5 itinerant system.
electronic state accompanied by unusual moment reorientation in NpRhGaJonen, Shintaro; Metoki, Naoto; Honda, Fuminori; Kaneko, Koji; Yamamoto, Etsuji; Haga, Yoshinori; Aoki, Dai*; Homma, Yoshiya*; Shiokawa, Yoshinobu; Onuki, Yoshichika
Journal of the Physical Society of Japan, 75(Suppl.), p.41 - 43, 2006/08
Elastic neutron scattering experiments have been carried out in order to reveal the magnetic structure and 5f electronic state of NpRhGa. This material exhibits two successive antiferromagnetic transition at T
= 36 K and T
= 33 K, respectively. A-type antiferromagnetic structure with the propagation vector q = (0 0 1/2) has been revealed below T. We found a remarkable change in the moment direction, namely the Np moment is parallel and perpendicular to the c-axis for T T T and T T, respectively. The magnetic moment exhibits a remarkable jump at T, indicating that the moment reorientation is associated with the change of 5f electronic state. The observed magnetic form factor indicates the dominant contribution of the orbital moment and revealed an itinerant character of the 5f electrons.
Jonen, Shintaro; Metoki, Naoto; Honda, Fuminori; Kaneko, Koji; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji; Haga, Yoshinori; Shiokawa, Yoshinobu; Onuki, Yoshichika
Physica B; Condensed Matter, 378-380, p.1018 - 1020, 2006/05
Times Cited Count：7 Percentile：35.01(Physics, Condensed Matter)The magnetic structure of NpRhGa has been investigated by neutron scattering. NpRhGa exhibits two antiferromagnetic phases with transition temperatures at T = 36 K and T = 33 K. Neutron scattering experiments revealed an antiferromagnetic structure with propagation vector q = (0 0 1/2) for both, where the Np magnetic moments are oriented parallel to the c-axis for T T T and parallel to the [110] direction on basal plane for T T. At T the reorientation of magnetic moments is accompanied by a sudden increase of magnetic moments, indicative of the first order transition. The magnetic form factor revealed a dominant contribution of the orbital moments.
Honda, Fuminori; Metoki, Naoto; Kaneko, Koji; Jonen, Shintaro; Yamamoto, Etsuji; Aoki, Dai*; Shiokawa, Yoshinobu*; Shiokawa, Yoshinobu; Onuki, Yoshichika
Physica B; Condensed Matter, 378-380, p.1009 - 1010, 2006/05
Times Cited Count：6 Percentile：31.12(Physics, Condensed Matter)no abstracts in English
Metoki, Naoto; Honda, Fuminori; Kaneko, Koji; Jonen, Shintaro; Yamamoto, Etsuji; Haga, Yoshinori; Aoki, Dai*; Homma, Yoshiya*; Shiokawa, Yoshinobu; Onuki, Yoshichika
no journal, ,
no abstracts in English
Metoki, Naoto; Yamamoto, Etsuji; Honda, Fuminori*; Kaneko, Koji; Jonen, Shintaro; Mizuno, Fumio; Sugai, Takashi*; Aoki, Dai*; Homma, Yoshiya*; Shiokawa, Yoshinobu*
no journal, ,
no abstracts in English
by neutron scatteringSugai, Takashi; Mizuno, Fumio; Jonen, Shintaro*; Kaneko, Koji; Metoki, Naoto; Haga, Yoshinori; Aoki, Dai*; Homma, Yoshiya*; Shiokawa, Yoshinobu*
no journal, ,
Np-115 compounds show various magenetic structures by changing the transision metal. NpFeGa is the antiferromagnet which orders Q=(1/2 1/2 0) with two steps. Additionally NpFeGa has the magnetic moment not only on Np site but also on Fe site. By analyzing the magnetic form factor, we obtained that it was possible for Fe to have the orbital magnetic moment. It is interesting because ordinarily the orbital magnetic moment of Fe is quenched.
by neutron diffractionJonen, Shintaro; Kaneko, Koji; Metoki, Naoto; Mizuno, Fumio*; Honda, Fuminori*; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji; Shiokawa, Yoshinobu*; Onuki, Yoshichika*
no journal, ,
no abstracts in English
by neutron scatteringSugai, Takashi; Mizuno, Fumio; Jonen, Shintaro*; Kaneko, Koji; Metoki, Naoto; Haga, Yoshinori; Aoki, Dai*; Homma, Yoshiya*; Shiokawa, Yoshinobu*
no journal, ,
no abstracts in English
(R: Nd, Tb, Dy and Ho)Hieu, N. V.*; Jonen, Shintaro; Metoki, Naoto; Sugiyama, Kiyohiro*; Settai, Rikio*; Matsuda, Tatsuma; Haga, Yoshinori; Takeuchi, Tetsuya*; Hagiwara, Masayuki*; Onuki, Yoshichika*
no journal, ,
The magnetic structure and the metamagnetic transition in RRhIn (R=Nd, Tb, Dy and Ho), which belong to the isostructural family of heavy fermion superconductor CeTIn and PuTGa (T=transition metal), were studied by neutron scattering. We found an antiferromagnetic structure with q
=(1/2 0 1/2) in the ground state in RRhIn. But, in the DyRhIn and HoRhIn, a weak magnetic reflection in q
=(1/2 1/2 0) was observed, suggesting a complex magnetic structure. From magnetic entropy measurements, it has been recognized that the orbital degree of freedom plays important role in DyRhIn and HoRhIn.
Honda, Fuminori; Metoki, Naoto; Kaneko, Koji; Jonen, Shintaro; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji; Shiokawa, Yoshinobu*; Onuki, Yoshichika*
no journal, ,
no abstracts in English
Honda, Fuminori; Metoki, Naoto; Kaneko, Koji; Jonen, Shintaro; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji; Shiokawa, Yoshinobu*; Onuki, Yoshichika*
no journal, ,
The discovery of the heavy fermion superconductivity below 19 K in PuCoGaproved that there is potential and fruitful field of interest spreading out in actinides science, where the quantum mechanical degrees of freedom of 
electron are playing a crucial role. Since AnTGa can be grown with various actinides and transition metal elements, it is an excellent candidate for studying the multiple electron system. Recently, we have extended our research activity into neutron scattering for Np
Ga (: Fe, Co, Ni and Rh) compounds in order to get deep insight about the multipolar degree of freedom in this system. We have revealed that NpGa exhibits various antiferromagnetic structures of A-, C-, G-type, ferromagnetic ordering and cant magnetism, which are the reminiscent of manganese perovskites. The remarkable successive magnetic transition associated with reorientation and considerable increase of magnetic moment found in NpNiGa and NpRhGa is a signature for the change in the electronic states, involving the possibility of the quadrupole order in itinerant system. We will sketch out a diverse electronic properties realized in NpGa in terms of the competing magnetic and quadrupolar interactions.
by neutron scatteringJonen, Shintaro; Metoki, Naoto; Honda, Fuminori; Kaneko, Koji; Aoki, Dai*; Yamamoto, Etsuji; Haga, Yoshinori; Shiokawa, Yoshinobu*; Onuki, Yoshichika
no journal, ,
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.
electron system NpTGaMetoki, Naoto; Kaneko, Koji; Honda, Fuminori*; Jonen, Shintaro; Yamamoto, Etsuji; Haga, Yoshinori; Aoki, Dai*; Homma, Yoshiya*; Shiokawa, Yoshinobu*; Onuki, Yoshichika
no journal, ,
Systematic neutron scattering study revealed the diverse magnetic properties in NpTGa (T: Fe, Co, Ni, Rh, Pt) with A-, C-, G-type antiferro- and ferromagnetic and canted structure. We found that the successive magnetic transition in NpTGa (T = Fe, Ni, Rh) is an electronic transition between the high- and low-moment states. We argue that the orbital degree of freedom in the itinerant 5 compounds plays an important role for the magnetic properties. A localized model explains the ordering and phase diagram, where the quadrupole order parameter coexists with magnetic dipole in the ground state of NpTGa (T = Fe, Ni, Rh). It means that a localized model is a powerful tool to describe the static property, which is the temporal and spatial average of the fluctuating itinerant system. Our study indicates the existence of the multipole order in itinerant many body 5, where a new theoretical framework is necessary to describe these highly interesting phenomena.
