Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Zhu, J.-X.*; Ronning, F.*; Thompson, J. D.*; Kotegawa, Hisashi*; To, Hideki*; Suzuki, Kohei*; Oshima, Yoshiki*; et al.
Physical Review B, 106(23), p.235152_1 - 235152_8, 2022/12
We investigate the electronic state of Ni-substituted CeCoNiIn by nuclear quadrupole and magnetic resonance (NQR/NMR) techniques. The heavy fermion superconductivity below K for is suppressed by Ni substitutions, and reaches zero for . The In NQR spectra for and 0.25 can be explained by simulating the electrical field gradient that is calculated for a virtual supercell with density functional theory. The spin-lattice relaxation rate indicates that Ni substitution weakens antiferromagnetic correlations that are not localized near the substituent but instead are uniform in space. The temperature () dependence of for shows a maximum around K and decreases toward almost zero when temperature is further reduced as if a gap might be opening in the magnetic excitation spectrum; however, the magnetic specific heat and the static magnetic susceptibility evolve smoothly through with a dependence. The peculiar T dependence of and non-Fermi-liquid specific heat and susceptibility can be interpreted in a unified way by assuming nested antiferromagnetic spin fluctuations in a quasi-two-dimensional electronic system.
Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Zhu, J.-X.*; Ronning, F.*; Thompson, J. D.*; Ramakrishna, S. K.*; Reyes, A. P.*; Suzuki, Kohei*; Oshima, Yoshiki*; et al.
Physical Review B, 104(8), p.085106_1 - 085106_12, 2021/08
Antiferromagnetism in a prototypical quantum critical metal CeCoIn is known to be induced by slight substitutions of non-magnetic Zn atoms for In. In nominally 7% Zn substituted CeCoIn, an antiferromagnetic (AFM) state coexists with heavy fermion superconductivity. Heterogeneity of the electronic states is investigated in Zn doped CeCoIn by means of nuclear quadrupole and magnetic resonances (NQR and NMR). Site-dependent NQR relaxation rates indicate that the AFM state is locally nucleated around Zn substituents in the matrix of a heavy fermion state, and percolates through the bulk at the AFM transition temperature . At lower temperatures, an anisotropic superconducting (SC) gap below the SC transition temperature , and the SC state permeates through the AFM regions via a SC proximity effect. Applying an external magnetic field induces a spin-flop transition near 5 T, reducing the volume of the AFM regions. Consequently, a short ranged inhomogeneous AFM state survives and coexists with a paramagnetic Fermi liquid state at high fields.
Lessux, G. G.*; Sakai, Hironori; Hattori, Taisuke*; Tokunaga, Yo; Kambe, Shinsaku; Kuhns, P. L.*; Reyes, A. P.*; Thompson, J. D.*; Pagliuso, P. G.*; Urbano, R. R.*
Physical Review B, 101(16), p.165111_1 - 165111_6, 2020/04
CeRhIn is a Kondo-lattice prototype in which a magnetic field 31T induces an abrupt Fermi-surface (FS) reconstruction and pronounced in-plane electrical transport anisotropy all within its antiferromagnetic state. Here we report low-temperature nuclear magnetic resonance (NMR) measurements revealing a pronounced decrease in the In formal Knight shift, without changes in crystal or magnetic structures, of CeRhIn at fields () spanning . We discuss the emergent state above in terms of a change in Ce's 4 orbitals that arises from field-induced evolution of crystal-electric field (CEF) energy levels. This change in orbital character enhances hybridization between the 4 and the conduction electrons that leads ultimately to an itinerant quantum-critical point at 50T.
Sakai, Hironori; Tokunaga, Yo; Haga, Yoshinori; Kambe, Shinsaku; Ramakrishna, S. K.*; Reyes, A. P.*; Rosa, P. F. S.*; Ronning, F.*; Thompson, J. D.*; Fisk, Z.*; et al.
JPS Conference Proceedings (Internet), 30, p.011169_1 - 011169_6, 2020/03
Uranium disulfide -US showing a semimetal-to-semiconductor crossover has been investigated by the nuclear magnetic resonance (NMR) technique for S nuclei with the nuclear spin of . Since the natural concentration 0.76% of NMR active S nuclei is too dilute, the isotopic enrichment to 50% has been carried out for the single crystal growth. The S NMR spectra have been successfully obtained using a single crystal of -US with external fields along the crystallographic axis. The S sites assignments have been made based on these NMR spectra.
Dioguardi, A. P.*; Yasuoka, Hiroshi*; Thomas, S. M.*; Sakai, Hironori; Cary, S. K.*; Kozimor, S. A.*; Albrecht-Schmitt, T. E.*; Choi, H. C.*; Zhu, J.-X.*; Thompson, J. D.*; et al.
Physical Review B, 99(3), p.035104_1 - 035104_6, 2019/01
We present a detailed nuclear magnetic resonance (NMR) study of Pu in bulk and powdered single-crystal plutonium tetraboride (PuB), which has recently been investigated as a potential correlated topological insulator. The Pu NMR spectra are consistent with axial symmetry of the shift tensor showing for the first time that Pu NMR can be observed in an anisotropic environment and up to room temperature. The temperature dependence of the Pu shift, combined with a relatively long spin-lattice relaxation time (), indicate that PuB adopts a nonmagnetic state with gaplike behavior consistent with our density functional theory calculations. The temperature dependencies of the NMR Knight shift and imply bulk gaplike behavior confirming that PuB is a good candidate topological insulator.
Chadwick, M. B.*; Capote, R.*; Trkov, A.*; Herman, M. W.*; Brown, D. A.*; Hale, G. M.*; Kahler, A. C.*; Talou, P.*; Plompen, A. J.*; Schillebeeckx, P.*; et al.
Nuclear Data Sheets, 148, p.189 - 213, 2018/02
The CIELO collaboration has studied neutron cross sections on nuclides that significantly impact criticality in nuclear facilities - U, U, Pu, Fe, O and H - with the aim of improving the accuracy of the data and resolving previous discrepancies in our understanding. This multi-laboratory pilot project, coordinated via the OECD/NEA Working Party on Evaluation Cooperation (WPEC) Subgroup 40 with support also from the IAEA, has motivated experimental and theoretical work and led to suites of new evaluated libraries that accurately reflect measured data and also perform well in integral simulations of criticality. This report summarizes our results and outlines plans for the next phase of this collaboration.
Chadwick, M. B.*; Capote, R.*; Trkov, A.*; Kahler, A. C.*; Herman, M. W.*; Brown, D. A.*; Hale, G. M.*; Pigni, M.*; Dunn, M.*; Leal, L.*; et al.
EPJ Web of Conferences, 146, p.02001_1 - 02001_9, 2017/09
The CIELO collaboration has studied neutron cross sections on nuclides (O, Fe, U and Pu) that significantly impact criticality in nuclear technologies with the aim of improving the accuracy of the data and resolving previous discrepancies in our understanding. This multi-laboratory pilot project, coordinated via the OECD/NEA Working Party on Evaluation Cooperation (WPEC) Subgroup 40 with support also from the IAEA, has motivated experimental and theoretical work and led to suites of new evaluated libraries that accurately reflect measured data and also perform well in integral simulations of criticality.
Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Ghimire, N. J.*; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*
Journal of Physics; Conference Series, 868(1), p.012012_1 - 012012_5, 2017/07
Al NMR experiments have been performed using a single crystal of CeRhAlSi. In the paramagnetic state, Knight shifts, quadrupolar frequency, and asymmetric parameter of electrical field gradient on the Al sites have been determined, which has a local orthorhombic symmetry. The transferred hyperfine coupling constants are also determined. The relaxation rates suggest that 4 electrons behave as local moments in the high temperatures. From the NMR spectral analyses, the antiferromagnetic structures are discussed.
Sakai, Hironori; Ronning, F.*; Hattori, Takanori; Tokunaga, Yo; Kambe, Shinsaku; Zhu, J.-X.*; Wakeham, N.*; Yasuoka, Hiroshi; Bauer, E. D.*; Thompson, J. D.*
Journal of Physics; Conference Series, 807(3), p.032001_1 - 032001_6, 2017/04
We have used nuclear quadrupole resonance (NQR) to probe microscopically the response of a prototypical quantum critical metal CeCoIn to substitutions of small amounts of Cd for In. Approximately half of the Cd substituents induce local Ce moments in their close proximity, as observed by site-dependent longitudinal nuclear spin relaxation rates . To reaffirm that localized moments are induced around the Cd substituents, we find a Gaussian spin-echo decay rate of transverse nuclear spin relaxation. Further, for the NQR subpeak is found to be proportional to temperatures, again indicating local moments fluctuations around the Cd substituents, while that for the NQR main peak shows a -dependence. The latter temperature dependence is close to 0.75 in pure CeCoIn and indicates that the bulk electronic state is located close to a two dimensional quantum critical instability.
Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Ghimire, N. J.*; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*
Physical Review B, 93(1), p.014402_1 - 014402_9, 2016/01
Al nuclear magnetic resonance (NMR) experiments have been performed on a single crystal of CeRhAlSi, which is an antiferromagnetic Kondo-lattice compound with successive antiferromagnetic transitions of =14 K and =9 K at zero external field. In the paramagnetic state, the Knight shifts, quadrupolar frequency, and asymmetric parameter of electrical field gradient on the Al sites have been determined, which have local orthorhombic symmetry. The transferred hyperfine coupling constants are also determined. Analysis of the NMR spectra indicates that a commensurate antiferromagnetic structure exists below , but an incommensurate modulation of antiferromagnetic moments is present in the antiferromagnetic state between and . The spin-lattice relaxation rate suggests that the electrons behave as local moments at temperatures above .
Sakai, Hironori; Ronning, F.*; Zhu, J.-X.*; Wakeham, N.*; Yasuoka, Hiroshi; Tokunaga, Yo; Kambe, Shinsaku; Bauer, E. D.*; Thompson, J. D.*
Physical Review B, 92(12), p.121105_1 - 121105_5, 2015/09
Chemical substitutions are used commonly to tune a magnetic transition to zero temperature, but the resulting non-Fermi liquid (NFL) behavior is non-universal. We have used nuclear quadrupole resonance (NQR) to probe microscopically the response of a prototypical quantum-critical metal CeCoIn to substitutions of small amounts of Sn and Cd for In. These substituents induce very different local electronic environments as observed by site dependent spin lattice relaxation rates that influence the NFL behavior. The effects found here illustrate the need for care in interpreting NFL properties determined by macroscopic measurements.
Sakai, Hironori; Urbano, R. R.*; Tokunaga, Yo; Kambe, Shinsaku; Suzuki, Michito; Kuhns, P. L.*; Reyes, A. P.*; Tobash, P. H.*; Ronning, F.*; Bauer, E. D.*; et al.
Physical Review Letters, 112(23), p.236401_1 - 236401_5, 2014/06
Very high field Si-NMR measurements using a fully Si-enriched URuSi single crystal were carried out in order to microscopically investigate the "hidden order" (HO) state and adjacent magnetic phases in the high field limit. At the lowest measured temperature of 0.4 K, a clear anomaly reflecting a Fermi surface instability near 22 T inside the HO state is detected by the Si shift, . Moreover, a strong enhancement of develops near a critical field T, and the Si-NMR signal disappears suddenly at , indicating the total suppression of the HO state. Nevertheless, a weak and shifted Si-NMR signal reappears for fields higher than at 4.2 K, providing evidence for a magnetic structure within the magnetic phase caused by the Ising-type anisotropy of the uranium ordered moments.
Koutroulakis, G.*; Yasuoka, Hiroshi; Chudo, Hiroyuki; Tobash, P. H.*; Mitchell, J. N.*; Bauer, E. D.*; Thompson, J. D.*
New Journal of Physics (Internet), 16, p.053019_1 - 053019_12, 2014/05
We report In nuclear quadrupolar resonance (NQR) measurements on the heavy-fermion superconductor PuCoIn, in the temperature range 0.29 K 75 K. The NQR parameters for the two crystallographically inequivalent In sites are determined, and their temperature dependence is investigated. A linear shift of the quadrupolar frequency with lowering temperature below the critical value is revealed, in agreement with the prediction for composite pairing. The nuclear spin-lattice relaxation rate clearly signals a superconducting (SC) phase transition at 2.3 K, with strong spin fluctuations, mostly in-plane, dominating the relaxation process in the normal state near to . Analysis of the data in the SC state suggests that PuCoIn is a strong-coupling -wave superconductor.
Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*
Physical Review Letters, 112(20), p.206401_1 - 206401_5, 2014/05
Single crystals of the heavy-fermion antiferromagnet CePtIn with a Nel temperature () of 5.2 K at ambient pressure have been investigated by zero-field In-nuclear magnetic/quadrupole resonance (NMR/NQR) measurements as a function of applied pressure. Within the antiferromagnetic state the character of Ce's electron appears to change from localized to itinerant-like at GPa, approximately the pressure where superconductivity first emerges. With increased pressure, the superconducting transition reaches a maximum just at or slighty before antiferromagnetic order disappears, and not at the pressure GPa where the steeply decreasing Nel boundary extrapolates to zero temperature. For , the spin relaxation rate drops sharply by more than two orders of magnitude at , suggestive of a first order transition.
Chadwick, M. B.*; Dupont, E.*; Bauge, E.*; Blokhin, A.*; Bouland, O.*; Brown, D. A.*; Capote, R.*; Carlson, A. D.*; Danon, Y.*; De Saint Jean, C.*; et al.
Nuclear Data Sheets, 118, p.1 - 25, 2014/04
CIELO (Collaborative International Evaluated Library Organization) provides a new working paradigm to facilitate evaluated nuclear reaction data advances. It brings together experts from across the international nuclear reaction data community to identify and document discrepancies among existing evaluated data libraries, measured data, and model calculation interpretations, and aims to make progress in reconciling these discrepancies to create more accurate ENDF-formatted files. The focus will initially be on a small number of the highest-priority isotopes, namely H, O, Fe, U, and Pu. This paper identifies discrepancies between various evaluations of the highest priority isotopes. The evaluated data for these materials in the existing nuclear data libraries are reviewed, and some integral properties are given. The paper summarizes a program of nuclear science and computational work needed to create the new CIELO nuclear data evaluations.
Chudo, Hiroyuki; Koutroulakis, G.*; Yasuoka, Hiroshi; Bauer, E. D.*; Tobash, P. H.*; Mitchell, J. N.*; Thompson, J. D.*
Journal of Physics; Condensed Matter, 26(3), p.036001_1 - 036001_5, 2014/01
The results of In nuclear quadrupole resonance (NQR) measurements on PuIn are reported. Three of the four NQR lines of In expected for nuclear spin =9/2 are observed. The equal spacing of these lines at 20 K yields the NQR frequency of =10.45 MHz, and the asymmetry parameter of the electric field gradient, =0. The NQR line profile and the nuclear spin-lattice relaxation rate display an abrupt change at 14 K, which is associated with the onset of long-range antiferromagnetic order. The temperature dependences of the staggered magnetization , extracted from the NQR spectra, and below =14 K are well explained by the self-consistent renormalization (SCR) theory for spin fluctuations. In addition, scaling between and is also consistent with the predictions of SCR theory, providing further evidence that PuIn is a weak itinerant antiferromagnet in which spin fluctuations around the antiferromagnetic wave vector play a major role in the system's behavior at finite temperatures.
Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Lee, H.*; Sidorov, V. A.*; Tobash, P. H.*; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*
Journal of Physics; Conference Series, 391, p.012057_1 - 012057_4, 2012/12
Zero-field In-nuclear magnetic resonance (NMR) has been used to study single crystals of CePtIn, a heavy-fermion antiferromagnet with a Nel temperature () of 5.2 K at ambient pressure. The NMR spectra under zero field near the 3 line of the orthorhombic In(3) sites are tracked by temperatures down to 1.6 K and by hydrostatic pressures up to 2.4 GPa. These data reveal the coexistence of commensurate (C) and incommensurate (IC) antiferromagneic orders at ambient pressure and that the C-AFM ordering is stabilized by increasing pressures where bulk superconductivity emerges. We will show the recent data of spectra and nuclear relaxation rates () under pressures.
Sakai, Hironori; Chudo, Hiroyuki; Tokunaga, Yo; Kambe, Shinsaku; Haga, Yoshinori; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*; Homma, Yoshiya*; Aoki, Dai*; et al.
Journal of the Physical Society of Japan, 81(Suppl.B), p.SB003_1 - SB003_6, 2012/12
In the so-called 115 family members with chemical formulae of CeIn (=Co, Rh, Ir) and Ga (=U, Np, Pu), our analysis of the Knight shift and spin-lattice relaxation rates suggests that larger XY-type anisotropy in the antiferromagnetic spin fluctuations in the normal states would favor -wave superconductivity with higher . In order to examine this working hypothesis, the anisotropy ratios of antiferromagnetic fluctuations are derived from our NMR results for the superconductor NpPdAl and antiferromagnet CePdAl, which are tetragonal compounds with a 115-related structure. CePdAl shows Ising-type anisotropy, which is the same anisotropy as in the ordered state. On the other hand, NpPdAl shows XY-type anisotropy just above .
Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Baumbach, R. E.*; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*
Physical Review B, 86(9), p.094402_1 - 094402_8, 2012/09
Nuclear magnetic resonance (NMR) studies using B and Ga have been performed on the tetragonal Ce-based ferromagnet CeRuGaB. The Knight shifts for the nuclei show an Ising-type anisotropy along the axis, similar to results from the static susceptibility. From the Knight shift measurements, the hyperfine coupling constants have been determined. The anisotropy of the spin- lattice relaxation rates indicates that the anisotropy of spin fluctuations are also Ising-like along the axis. The localized character of the electrons in this system is discussed.
Ross, T. J.*; Beausang, C. W.*; Hughes, R. O.*; Allmond, J. M.*; Angell, C.; Basunia, M. S.*; Bleuel, D. L.*; Burke, J. T.*; Casperson, R. J.*; Escher, J. E.*; et al.
Physical Review C, 85(5), p.051304_1 - 051304_5, 2012/05
The surrogate reaction technique has been employed to cross sections in the actinide region to a precision of 20%, but in the rare earth region a factor of 2-3 discrepancy exists between the directly measured and extracted surrogate cross sections. A possible origin of this discrepancy lies in differences between the initial spin/parity population distribution. To investigate this, the angular momentum transfer of the surrogate reaction in Gd nuclei has been measured.