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Ni
In
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
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)We investigate the electronic state of Ni-substituted CeCoNi
In 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.
; In NQR/NMR and 
Co NMR studySakai, 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
Times Cited Count：3 Percentile：27.71(Materials Science, Multidisciplinary)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.
S nuclear magnetic resonance spectra of uranium disulfide 
-US
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.
Pu nuclear magnetic resonance in the candidate topological insulator PuB
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
Times Cited Count：8 Percentile：37.59(Materials Science, Multidisciplinary)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.
SiSakai, 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
Times Cited Count：1 Percentile：49.63(Physics, Applied)
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.
; NQR relaxation ratesSakai, 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
Times Cited Count：3 Percentile：68.62(Physics, Condensed Matter)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.
Si; An Al NMR studySakai, 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
Times Cited Count：2 Percentile：10.64(Materials Science, Multidisciplinary)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
Times Cited Count：19 Percentile：62.1(Materials Science, Multidisciplinary)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.
Si; High magnetic field nuclear magnetic resonance to 40 TSakai, 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
Times Cited Count：7 Percentile：49.06(Physics, Multidisciplinary)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.
In
; Microscopic phase diagram determined by In NMR and NQRSakai, 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
Times Cited Count：14 Percentile：65.73(Physics, Multidisciplinary)Single crystals of the heavy-fermion antiferromagnet CePt
In
with a N
el 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.
InSakai, 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
Times Cited Count：4 Percentile：79.46(Physics, Multidisciplinary)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.
Al and NpPdAlSakai, 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
Times Cited Count：7 Percentile：46.7(Physics, Multidisciplinary)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 .
-localized ferromagnet CeRuGaBSakai, 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
Times Cited Count：11 Percentile：41.17(Materials Science, Multidisciplinary)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.
AlB; A Local-moment 4 magnet with a complex -
phase diagramRaumbach, R. E.*; Chudo, Hiroyuki; Yasuoka, Hiroshi; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*
Physical Review B, 85(9), p.094422_1 - 094422_7, 2012/03
Times Cited Count：31 Percentile：74.69(Materials Science, Multidisciplinary) using Co nuclear magnetic resonanceSakai, Hironori; Brown, S. E.*; Baek, S.-H.*; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*
Physical Review Letters, 107(13), p.137001_1 - 137001_5, 2011/09
Times Cited Count：16 Percentile：66.79(Physics, Multidisciplinary)Co nuclear spin lattice relaxation has been measured for the heavy-fermion superconductor CeCoIn in a range of applied fields directed parallel to the -axis. An enhanced normal state relaxation rate, observed at low temperatures and fields just above 
, is taken as a direct measure of the dynamical susceptibility and provides microscopic evidence for an antiferromagnetic instability. The results are well-described using the self-consistent renormalized theory for two-dimensional antiferromagnetic spin fluctuations, and parameters obtained in the analysis are applied to previously reported specific heat and thermal expansion data with good agreement.
studied by means of NMR/NQR techniquesSakai, Hironori; Kurita, Nobuyuki*; Miclea, C. F.*; Movshovich, R.*; Lee, H.-O.*; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*
Journal of the Physical Society of Japan, 80(Suppl.A), p.SA059_1 - SA059_3, 2011/07
The effect of dilute La substitution in CeLaRhIn
(0
x0.07) has been investigated microscopically by nuclear magnetic/quadrupole resonance (NMR/NQR). By the dilute La substitutions, the 4 lines for In(1) sites are found to be undisturbed and to have a reasonably narrow width, even in the ordered AF state. These 4 positions in the La-substituted CeRhIn indicate a decrease of the internal field on In(1) sites, due to the reduction of hyperfine couplings by La substitutions. The spin-lattice relaxation rates (
) using these 4 lines at high temperatures can be understood by the reduction of exchange energy and effective moments. On the other hand, in the AF ordered state can be explained by a gapped Fermi surface and spin fluctuations of uncompensated localized Ce moments near the La ions.
In by pressure up to 2.4 GPa; In NMR and NQR under zero fieldSakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Lee, H.-O.*; Sidorov, V. A.*; Tobash, P. H.*; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*
Physical Review B, 83(14), p.140408_1 - 140408_4, 2011/04
Times Cited Count：22 Percentile：65.72(Materials Science, Multidisciplinary)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. Narrow linewidths of In-nuclear quadrupolar resonance (NQR) spectra are observed from each of three crystallographically inequivalent In(1), In(2) and In(3) sites. 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 and incommensurate antiferromagnetic (AFM) orders at ambient pressure and that the commensurate ordering is stabilized by increasing pressures where bulk superconductivity emerges.
Bauer, E. D.*; Yang, Y.-F.*; Capan, C.*; Urbano, R. R.*; Miclea, C. F.*; Sakai, Hironori; Ronning, F.*; Graf, M. J.*; Balatsky, A. V.*; Movshovich, R.*; et al.
Proceedings of the National Academy of Sciences of the United States of America, 108(17), p.6857 - 6861, 2011/04
Times Cited Count：36 Percentile：81.82(Multidisciplinary Sciences)Here, we report a manifestation of electronic inhomogeneity in a strongly correlated -electron system, using CeCoIn as an example. A thermodynamic analysis of its superconductivity, combined with nuclear quadrupole resonance measurements, shows that nonmagnetic impurities (Y, La, Yb, Th, Hg, and Sn) locally suppress unconventional superconductivity, generating an inhomogeneous electronic "Swiss cheese" due to disrupted periodicity of the Kondo lattice. Our analysis may be generalized to include related systems, suggesting that electronic inhomogeneity should be considered broadly in Kondo lattice materials.
Co NMR study in PuCoGaBaek, S.-H.*; Sakai, Hironori; Bauer, E. D.*; Mitchell, J. N.*; Kennison, J. A.*; Ronning, F.*; Thompson, J. D.*
Physical Review Letters, 105(21), p.217002_1 - 217002_4, 2010/11
Times Cited Count：13 Percentile：61.59(Physics, Multidisciplinary)We report results of Co nuclear magnetic resonance measurements on a single crystal of superconducting PuCoGa in its normal state. The nuclear spin-lattice relaxation rates and the Knight shifts as a function of temperature reveal an anisotropy of spin fluctuations with finite wave vector 
. By comparison with the isostructural members, we conclude that antiferromagnetic 
-type anisotropy of spin fluctuations plays an important role in mediating superconductivity in these heavy fermion materials.
In and PuGa (=Co, Rh)Sakai, Hironori; Kambe, Shinsaku; Tokunaga, Yo; Haga, Yoshinori; Baek, S.-H.*; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*
Materials Research Society Symposium Proceedings, Vol.1264, p.69 - 79, 2010/10
The anisotropy of antiferromagnetic spin fluctuations has been investigated microscopically in the heavy fermion systems of CeIn and PuGa (=Co, Rh) by means of nuclear magnetic resonance (NMR). Both systems are known to be relatively high- superconductors among the heavy fermion systems, especially PuCoGa, which has a =18.5 K almost one order of magnitude larger than for CeCoIn (=2.3 K). Analysis of the Knight shift and spin-lattice relaxation rates suggests XY-type anisotropy in the antiferromagnetic spin fluctuations in the normal states of these unconventional superconductors. Moreover, the 115 superconductors with larger XY-type fluctuations have a higher , compared with the anisotropy of spin fluctuations in the related paramagnetic system UFeGa and antiferromagnets UPtGa, NpCoGa, NpFeGa.
