Low-Temperature Magnetization Study on the Phase IV Ordering in CexLa1-xB6under [111] Uniaxial Pressures

Morie, Takaaki; Sakakibara, Toshiro; Tayama, Takashi; Kunii, S.

doi:10.1143/jpsj.73.2381

Cited by 18 publications

(11 citation statements)

References 17 publications

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“…In the present study, we found the enormous softenings of c 44 in the phase IV of 27 Furthermore, the breaking of the time reversal symmetry in the octupole ordering model may be consistent with the muon spin resonance and NMR experiment on the phase IV. 18,19 The octupole ordering of T β x + T β y + T β z lifts the Γ 8 quartet into a 6/10 singlet ground state, a first excited doublet state and a second excited singlet state.…”

Section: Discussionsupporting

confidence: 88%

Elastic Properties and Magnetic Phase Diagrams of Dense Kondo Compound Ce_0.75La_0.25B₆

et al. 2005

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We have investigated the elastic properties of the cubic dense Kondo compound Ce 0.75 La 0.25 B 6 by means of ultrasonic measurements. We have obtained magnetic fields vs. temperatures (H − T ) phase diagrams under magnetic fields along the crystallographic [001], [110] and [111] axes. An ordered phase IV showing the elastic softening of c 44 locates in low temperature region between 1.6 K and 1.1 K below 0.7 T in all field directions. The phase IV shows an isotropic nature with regard to the field directions, while the antiferro-magnetic phase III shows an anisotropic character. A remarkable softening of c 44 and a spontaneous trigonal distortion ε yz + ε zx + ε xy recently reported by Akatsu et al. in the phase IV favor a ferro-quadrupole (FQ) moment of O yz +O zx +O xy induced by an octupole ordering. KEYWORDS: Ce 0.75 La 0.25 B 6 , elastic constant, ultrasonic measurement, quadrupolar ordering, octupolar ordering, magnetic phase diagram, dense Kondo effect 1. Introduction CeB 6 and its substitutional compound Ce x La 1−x B 6 are well known as the typical examplesshowing multipolar orderings and the dense Kondo effect. In CeB 6 the Hund's ground multiplet 2 F 5/2 of Ce 3+ splits into a quartet Γ 8 ground state and a doublet Γ 7 excited state located at 540 K in the cubic crystal-electric-field (CEF). 1-4 The CEF ground state of Ce x La 1−x B 6 is also considered to be a quartet Γ 8 from the results of the magnetic susceptibility measurements. 4Because of the large CEF splitting energy, the low-temperature properties of Ce x La 1−x B 6 are dominated by the ground state quartet Γ 8 with SU(4) symmetry. The direct product Γ 8 ⊗ Γ 8 possesses fifteen quantum degrees of freedom consisting of three magnetic dipoles, five electric quadrupoles, and seven magnetic octupoles. 5 Actually CeB 6 undergoes successive transitions from higher temperature paramagnetic phase I into an antiferro-quadrupolar (AFQ) phase II at T Q = 3.3 K and further into an antiferro-magnetic (AFM) phase III below T N = 2.3 K in which the AFQ ordering coexists. 6, 7

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Section: Discussionsupporting

confidence: 88%

Elastic Properties and Magnetic Phase Diagrams of Dense Kondo Compound Ce_0.75La_0.25B₆

et al. 2005

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“…Since the Γ 8 quartet has three types of octupoles -T xyz , T α , and T β -in addition to dipoles and quadrupoles, it was argued that the magnetic octupoles are a possible candidate for the order parameter. Following these studies, the magnetization under uniaxial pressure, thermal expansion, and elastic constant measurements supported that the order parameter of phase IV is T β octupoles with Γ 5 symmetry of the point group O h ; [8][9][10][11] it is consistent with the exis- * E-mail address: kuwahara@phys.metro-u.ac.jp tence of internal magnetic fields detected by NMR 12 and µSR 13, 14 as well as a theoretical model. 15 Furthermore, evidence of the antiferro-octupolar ordering of T β with the same wave vector as k Q has recently been reported by the resonant X-ray scattering experiment and its detailed analysis, 16,17 although further studies are necessary for understanding the overall nature of phase IV in Ce x La 1−x B 6 .…”

Section: -11supporting

confidence: 55%

“…2,3 By doping La into the Ce site in this system, a new phase called phase IV appears below T IV = 1.7 K and 1.5 K in Ce x La 1−x B 6 for x = 0.75 and 0.70, respectively. [4][5][6][7][8][9][10][11] From the initial discovery of phase IV, 4-6 its characteristic magnetic phase diagram and anomalous bulk properties, which show the isotropic cusp of magnetization at T IV and the strong elastic softening of c 44 within phase IV, suggested that the ordering of phase IV must be different from any quadrupolar ordering. Since the Γ 8 quartet has three types of octupoles -T xyz , T α , and T β -in addition to dipoles and quadrupoles, it was argued that the magnetic octupoles are a possible candidate for the order parameter.…”

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confidence: 99%

Detection of Neutron Scattering from Phase IV of Ce_0.7La_0.3B₆: A Confirmation of the Octupole Order

et al. 2007

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We have performed a single crystal neutron scattering experiment on Ce0.7La0.3B6 to microscopically investigate the order parameter of phase IV. Below the phase transition temperature 1.5 K of phase IV, weak but distinct superlattice reflections at the scattering vector κ = () (h, l = odd number) have been observed for the first time by neutron scattering. The intensity of the superlattice reflections is stronger for high scattering vectors, which is quite different from the usual magnetic form factor of magnetic dipoles. This result directly evidences that the order parameter of phase IV has a complex magnetization density, consistent with the recent experimental and theoretical prediction in which the order parameter is the magnetic octupoles T β with Γ5 symmetry of the point group O h . Neutron scattering experiments using short wavelength neutrons, as done in this study, could become a general method to study the high-rank multipoles in f electron systems.

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“…76) Hence, multipole orders provide a solution to a certain type of ''hidden order'', for which order parameters are not identified in spite of evidence from the specific heat. Note that the octupole ordering model 64,65,74) in Ce x La 1Àx B 6 has also explained magnetic 97) and ultrasonic 147) anomalies. Another important topic is higher-rank tensors, which transform as a scalar in the point group.…”

Section: Introductionmentioning

confidence: 90%

Multipole Orders and Fluctuations in Strongly Correlated Electron Systems

2009

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In this paper we review experimental and theoretical results on higher electronic multipoles in solids with strong correlations. Recent experiments and their theoretical interpretation have confirmed the ordering of octupoles and even higher multipoles in rare-earth and actinide compounds with f electrons. The concept of multipoles is critically examined in point groups where spherical tensors of different ranks mix. Using a phenomenological approach, we demonstrate how linear and nonlinear couplings of different multipoles lead to rich phase diagrams and anomalies in physical observables. As actual representative systems, we first consider Ce x La 1Àx B 6 , for which resonant X-ray scattering probed the octupole order for the first time, and NpO 2 , where quadrupoles induced by the octupole order have been observed. We then consider a class of compounds called skutterudites as the most convenient system for systematic study. Particular emphasis is placed on the ordering of scalar components from fourth-rank tensors (hexadecapoles) and sixth-rank tensors (hexacontatetrapoles). A comparison of a skutterudite PrFe 4 P 12 and URu 2 Si 2 is made, where much fewer carriers remain in the ordered states than in the disordered phase. The even number (two) of f electrons per site in Pr 3þ or U 4þ makes the system free from the Kramers degeneracy, in contrast to standard models for Mott transitions. Hence, it is pointed out that multipole orders, particularly the scalar order, should provide a new route for studying the dichotomy between the itinerant and localized behaviors of electrons.

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Low-Temperature Magnetization Study on the Phase IV Ordering in Ce_xLa_1-xB₆under [111] Uniaxial Pressures

Cited by 18 publications

References 17 publications

Elastic Properties and Magnetic Phase Diagrams of Dense Kondo Compound Ce_0.75La_0.25B₆

Elastic Properties and Magnetic Phase Diagrams of Dense Kondo Compound Ce_0.75La_0.25B₆

Detection of Neutron Scattering from Phase IV of Ce_0.7La_0.3B₆: A Confirmation of the Octupole Order

Multipole Orders and Fluctuations in Strongly Correlated Electron Systems

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Low-Temperature Magnetization Study on the Phase IV Ordering in CexLa1-xB6under [111] Uniaxial Pressures

Cited by 18 publications

References 17 publications

Elastic Properties and Magnetic Phase Diagrams of Dense Kondo Compound Ce0.75La0.25B6

Elastic Properties and Magnetic Phase Diagrams of Dense Kondo Compound Ce0.75La0.25B6

Detection of Neutron Scattering from Phase IV of Ce0.7La0.3B6: A Confirmation of the Octupole Order

Multipole Orders and Fluctuations in Strongly Correlated Electron Systems

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Product

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Low-Temperature Magnetization Study on the Phase IV Ordering in Ce_xLa_1-xB₆under [111] Uniaxial Pressures

Elastic Properties and Magnetic Phase Diagrams of Dense Kondo Compound Ce_0.75La_0.25B₆

Elastic Properties and Magnetic Phase Diagrams of Dense Kondo Compound Ce_0.75La_0.25B₆

Detection of Neutron Scattering from Phase IV of Ce_0.7La_0.3B₆: A Confirmation of the Octupole Order