Kotai Butsuri, 55(7), p.285 - 296, 2020/07
Electron states are the main theme of "solid-state physics", which is essential for microscopic understanding of multipoles and superconductivity, etc. Rare earths (4) and actinides (5) provide variety of interesting states realized with competing interactions between the increasing number of electrons. Since crystal field splitting of many-body electron system is smaller than the bandwidth, (1) high resolution experiments are needed, (2) essentially no clear spectrum with well defined peaks is expected in itinerant Ce and U compounds, and (3) Np and Pu is strictly regulated. Therefore, systematic research on magnetic excitations by neutron scattering experiments of localized compounds and rare earth iso-structural reference is useful. We describe the electron states of heavy electron compounds NpPdAl and actinide and rare earth based iso-structural family.
Metoki, Naoto; Aczel, A. A.*; Aoki, Dai*; Chi, S.*; Fernandez-Baca, J. A.*; Griveau, J.-C.*; Hagiwara, Masato*; Hong, T.*; Haga, Yoshinori; Ikeuchi, Kazuhiko*; et al.
JPS Conference Proceedings (Internet), 30, p.011123_1 - 011123_6, 2020/03
Rare earths (4) and actinides (5) provide variety of interesting states realized with competing interactions between the increasing number of electrons. Since crystal field splitting of many-body electron system is smaller than the bandwidth, (1) high resolution experiments are needed, (2) essentially no clear spectrum with well defined peaks is expected in itinerant Ce and U compounds, and (3) Np and Pu is strictly regulated. Therefore, systematic research on magnetic excitations by neutron scattering experiments of localized compounds and rare earth iso-structural reference is useful. We describe the electron states of heavy electron compounds NpPdAl and actinide and rare earth based iso-structural family.
Metoki, Naoto; Aoki, Dai*; Griveau, J.-C.*; Otsuki, Junya*
Journal of the Physical Society of Japan, 89(2), p.024707_1 - 024707_6, 2020/02
The pseudo triplet ground state in the heavy-fermion superconductor NpPdAl was concluded. The magnetic susceptibility can be reproduced by the singlet ground state with the main component of and the first excited doublet dominated by at ,K. The magnetization curve can be explained from the effective local hamiltonian for pseudo spin =1 with () equivalent to the quadrupole operator . The specific heat can be described with the Kondo model normalized to give the entropy R, corresponding to the pseudo triplet state. The derived Kondo temperature ,K comparable to the level splitting ,K indicates the contribution of the excited doublet to the possible multi-channel Kondo effect.
Journal of the Physical Society of Japan, 89(2), p.025001_1 - 025001_2, 2020/02
Good correspondence of the and - coupling scheme can be realized in the -electron states of the heavy-fermion superconductor NpPdAl and the isostructural family. The rare-earth and actinide elements are under a common strong uniaxial point charge potential with tetragonal point symmetry . The systematic development of the -electron states can be understood in the coupling scheme of configuration (the number of electrons ). We can find the corresponding states in - coupling scheme with three -orbitals , and determined from CePdAl with configuration.
Metoki, Naoto; Haga, Yoshinori; Yamamoto, Etsuji; Matsuda, Masaaki*
Journal of the Physical Society of Japan, 87(11), p.114712_1 - 114712_9, 2018/11
The localized 5 states with 5 () configuration of U ion have been revealed in UPdAl. We found that the low-lying states are the same as PrPdAl flat orbitals with large are stabilized by a two-dimensional CEF potential in the unique crystal structure. The present study involves the valence crossover from tetravalent to trivalent in a series of AnPdAl, demonstrated by lattice and/or transport anomaly as well as many body effects in the vicinity of the boundary. The valence instability plays important role for the unusual heavy fermion superconductivity in NpPdAl.
Metoki, Naoto; Yamauchi, Hiroki; Suzuki, Hiroyuki*; Kitazawa, Hideaki*; Hagiwara, Masato*; Masuda, Takatsugu*; Aczel, A. A.*; Chi, S.*; Hong, T.*; Matsuda, Masaaki*; et al.
Journal of the Physical Society of Japan, 87(9), p.094704_1 - 094704_8, 2018/09
The -electron states of PrPdAl were revealed by neutron inelastic scattering. The flat -orbitals with large become stable under the two-dimensional CEF potential of unique crystal structure, which is the origin of the Ising anisotropy. A systematic understanding is possible in RPdAl based on this CEF potential. Especially the -type anisotropy in NpPdAl can be qualitatively understood with the positive Stevens factors. It mean that the local property is important for the physical properties of RPdAl including the heavy fermion superconductivity in NpPdAl.
Metoki, Naoto; Yamauchi, Hiroki; Suzuki, Hiroyuki*; Kitazawa, Hideaki*; Kamazawa, Kazuya*; Ikeuchi, Kazuhiko*; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro
Journal of the Physical Society of Japan, 87(8), p.084708_1 - 084708_7, 2018/08
Inelastic neutron scattering experiments were carried out in order to study the -electron states of NdPdAlThe CEF levels at 0K, 35.4K, 88.3K, 101.5K, and 198.8K were clarified from the excitation spectra. The ground state contains the orbital with as a main component due to a large negative BK, which is the origin of the strong uniaxial anisotropy. The estimated magnetic moment, the calculated susceptibility, magnetization curve, and specific heat are in good agreement with the experimental data. The existence of a common charge distribution with CePdAl and PrPdAl. Indicates that a localized character is important even in actinide-based iso-structural compounds as actually observed in UPdAl and also NpPdAl, in which the valence crossover plays important role for the heavy fermion superconductivity.
Metoki, Naoto; Yamauchi, Hiroki; Matsuda, Masaaki*; Fernandez-Baca, J. A.*; Watanuki, Ryuta*; Hagiwara, Masato*
Physical Review B, 97(17), p.174416_1 - 174416_10, 2018/05
Neutron polarization analysis has been carried out in order to clarify the magnetic structure of multiple order parameter -electron system NdB. We confirmed the non-collinear "all-in all-out" structure () of the in-plane moment. We found that the magnetic moment along the -axis showed diagonally antiferromagnetic structure (). The unusual magnetic ordering is phenomenologically understood via Landau theory. We also found that a long-period incommensurate modulation of the () antiferromagnetic structure of with the propagation = (0.14, 0.14, 0.1) and = (0.2, 0, 0.1) in phase III and IV, respectively. It is clear that the multipole degree-of-freedom based on pseudo-quartet -electron state play important role.
Yamauchi, Hiroki; Metoki, Naoto; Watanuki, Ryuta*; Suzuki, Kazuya*; Fukazawa, Hiroshi; Chi, S.*; Fernandez-Baca, J. A.*
Journal of the Physical Society of Japan, 86(4), p.044705_1 - 044705_9, 2017/04
Neutron diffraction experiments have been carried out to characterize the magnetic structures and order parameters in an intermediate phase of NdB showing the successive phase transitions at K, K, and K. The observed patterns in phase II () are successfully explained by postulating a planar structure with static magnetic moments in the tetragonal -plane. We have found that the magnetic structure in phase II can be uniquely determined to be a linear combination of noncolinear "all-in/all-out"-type and "vortex"-type antiferromagnetic structures. We propose that the quadrupolar interaction holds the key to stabilizing the noncollinear magnetic structure and quadrupolar order. Here, the frustration in the Shastry - Sutherland lattice would play an essential role in suppressing the dominance of the magnetic interaction.
Metoki, Naoto; Yamauchi, Hiroki; Kitazawa, Hideaki*; Suzuki, Hiroyuki*; Hagiwara, Masato*; Frontzek, M. D.*; Matsuda, Masaaki*; Fernandez-Baca, J. A.*
Journal of the Physical Society of Japan, 86(3), p.034710_1 - 034710_5, 2017/03
Magnetic structure of NdPdAl has been studied by means of neutron powder diffraction. We observed remarkable magnetic reflections with the modulation vector = (1/2 0 0) below the ordering temperature = 1.2 K. We found a collinear magnetic structure of Nd moment of 2.9(1) at 0.3 K parallel to the -axis, where the ferromagnetically ordered planes stack with four Nd layer period of ++-- sequence along the direction with the distance between adjuscent Nd layers to be . This is very similar to CePdAl with = (0.23 0.23 0) and the Ce moment parallel to the -axis. These structures with in-plane modulation is a consequence of the two dimensional nature of fermi surface topology in this family, coming from unique crystal structure with very long tetragonal unit cell and large distance 7 between the rare earth layers separated by Al and two Pd layers.
Metoki, Naoto; Sakai, Hironori; Suzuki, Michito; Yamamoto, Etsuji; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo*
JPS Conference Proceedings (Internet), 3, p.013011_1 - 013011_6, 2014/06
Uranium chalcogenides are highly interesting because of the variety of the physical properties from 5-based metal and Mott-Hibbard insulator. Especially dichalcogenide family exhibits a metal-insulator crossover depending on the chalcogenide elements, or under magnetic field and pressure. In this talk we present a recent result of our neutron scattering study on uranium dichalcogenide, which demonstrates that the metal-insulator crossover is related to the change of 5 character from localized to itinerant. The electronic structure related to this phenomenon is discussed based on the band calculation.
Metoki, Naoto; Sakai, Hironori; Yamamoto, Etsuji; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo*
Journal of the Korean Physical Society, 62(12), p.1782 - 1786, 2013/06
Magnetic excitation of a narrow gap semiconductor -USwas studied by means of neutron scattering. At low temperatures clear crystalline electric field (CEF) excitations were observed, indicating localized character of 5 electrons. The excitation energy 7 meV of the pseudo doublet state is consistent with the level scheme based on 5 configuration of U ions, which reproduces the magnetic susceptibility, magnetization, and specific heat. With elevating temperature the conductivity recovers with 5 carriers excited beyond the gap of 90 K. Simultaneously the CEF excitation becomes weak and broad, and is replaced by a quasi-elastic response of magnetic origin, indicating the crossover of 5 character from localized to itinerant.
Terada, Noriki*; Tsuchiya, Yoshinori*; Kitazawa, Hideaki*; Metoki, Naoto
Journal of the Korean Physical Society, 62(12), p.1905 - 1909, 2013/06
We have investigated magnetic and nonmagnetic impurity substitution effects on magnetic ordering of a frustrated isosceles triangular lattice antiferromagnet CuMnO by means of the magnetic neutron diffraction measurements on Cu(MnGa)O. While the magnetic wave vector of the magnetic ground state of "magnetically" substituted Cu(MnCu)O with x = 0:04 is Q = (-1/2 1/2 0), that in the "nonmagnetically" substituted Cu(MnGa)O with y =0.05, 0.15 and 0.20 is Q = (-1/2 1/2 1/2) that is identical to that of pure CuMnO. We discuss an influence of magnetic or nonmagnetic impurity substitution on the magnetic ordering of CuMnO, by comparing the results of Cu(MnGa)O with Cu(MnCux)O.
Metoki, Naoto; Sakai, Hironori; Yamamoto, Etsuji; Tateiwa, Naoyuki; Matsuda, Tatsuma; Haga, Yoshinori
Journal of the Physical Society of Japan, 82(5), p.055004_1 - 055004_2, 2013/05
The hidden order parameter in URuSi remains an open question for this quarter of a century. Many type of models have been proposed. The models predict unusual order parameters such as higher order multipole, dynamical origin, or very recently, "hastatic" order, accompanying Ising quasi-particles. We provide neutron scattering data measured at the wave vector =(003) for the in-plane magnetic component. The existence of the in-plane component in the order of 0.01 or 1010 Bohr magneton has been proposed by a recent theoretical studies. The data were obtained also under magnetic field up to 10 T along the  direction in order to reveal a possible type antiferro-quadrupole (AFQ) order at the propagation of =(001) proposed previously. Our data indicate that there is no in-plane magnetic component within the experimental accuracy of 0.004 Bohr magneton. Namely we could not obtain the results which support these theories.
Kaneko, Koji; Stockert, O.*; Skoulatos, M.*; Schneidewind, A.*; Takeuchi, Tetsuya*; Matsuda, Tatsuma; Haga, Yoshinori; Settai, Rikio*; Onuki, Yoshichika; Metoki, Naoto
Journal of the Physical Society of Japan, 81(Suppl.B), p.SB006_1 - SB006_7, 2012/12
Kimura, Tsunehisa*; Kimura, Fumiko*; Matsumoto, Kenji*; Metoki, Naoto
Neutron Diffraction, p.179 - 202, 2012/03
We report the results of the neutron scattering study on three dimensionally oriented pseudo single crystals under rotating magnetic field.
Hamon, 22(1), p.93 - 95, 2012/02
The International Conference on Research Reactors: Safe Management and Effective Utilization was Held in Rabat, the capital of the Kingdom of Morocco organized by IAEA hosted by the Kingdom of Morocco. Japan Atomic Energy Agency presented an invited talk about the (1) impact of the earthquake, (2) recent results, and (3) complementary research reactors and pulse neutron source. The talk was quoted in the summary talk which summarized as, "JRR-3 remains useful after J-PARC has been started. This and the construction of new research reactors, HANARO, OPAL FRM-II demonstrate an important role of the research reactors in the field of neutron science.", "JRR-3 has no serious damage from the earthquake, and the users look forward to an early re-operation."
Hase, Masashi*; Dnni, A.*; Ozawa, Kiyoshi*; Kitazawa, Hideaki*; Sakai, Osamu*; Pomjakushin, V. Y.*; Keller, L.*; Kaneko, Koji; Metoki, Naoto; Kakurai, Kazuhisa; et al.
Journal of Physics; Conference Series, 340, p.012066_1 - 012066_7, 2012/00
We determined the magnetic structure below K of the spin-5/2 antiferromagnetic (AF) trimer substance SrMnPO using neutron powder diffraction experiments. The incommensurate propagation vector is expressed as [0, , 0], due to competition between the nearest-neighbor and next-nearest-neighbor interactions in trimerized chains. The value of is 0.316 to 0.331, changing rapidly at K. We confirmed that the intra-trimer interaction is AF. The magnetic excitation peaks were obsereved at 0.46, 0.68, and 1.02 meV. The weak Q dependence indicates the discrete energy levels, which do not contradict the AF trimer model with the intra-trimer interaction value of 0.29 meV (3.4 K).
Hase, Masashi*; Matsuda, Masaaki*; Kaneko, Koji; Metoki, Naoto; Kakurai, Kazuhisa; Yang, T.*; Cong, R.*; Lin, J.*; Ozawa, Kiyoshi*; Kitazawa, Hideaki*
Physical Review B, 84(21), p.214402_1 - 214402_6, 2011/12
Masuda, Takatsugu*; Hagiwara, Masato*; Kondo, Yosuke*; Kaneko, Koji; Metoki, Naoto
Journal of the Physical Society of Japan, 80(11), p.113705_1 - 113705_4, 2011/11
We study a field-induced quantum phase in the weakly-coupled ferromagnetic frustrated chain LiCuVO by a neutron diffraction technique. A new incommensurate magnetic peak is observed at H 8.5 T. The field-dependent propagation vector is identified with the spin density wave correlation in the theoretically predicted magnetic quadrupole order. Quantum fluctuation, geometrical frustration, and interchain interaction induce an exotic spin density wave long-range order in the insulating magnet.