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Journal Articles

$$^{33}$$S nuclear magnetic resonance spectra of uranium disulfide $$beta$$-US$$_2$$

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 $$beta$$-US$$_2$$ showing a semimetal-to-semiconductor crossover has been investigated by the nuclear magnetic resonance (NMR) technique for $$^{33}$$S nuclei with the nuclear spin of $$I=3/2$$. Since the natural concentration 0.76% of NMR active $$^{33}$$S nuclei is too dilute, the isotopic enrichment to $$sim$$50% has been carried out for the single crystal growth. The $$^{33}$$S NMR spectra have been successfully obtained using a single crystal of $$beta$$-US$$_2$$ with external fields along the crystallographic $$c$$ axis. The S sites assignments have been made based on these NMR spectra.

Journal Articles

$$^{239}$$Pu nuclear magnetic resonance in the candidate topological insulator PuB$$_4$$

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:5 Percentile:30.83(Materials Science, Multidisciplinary)

We present a detailed nuclear magnetic resonance (NMR) study of $$^{239}$$Pu in bulk and powdered single-crystal plutonium tetraboride (PuB$$_4$$), which has recently been investigated as a potential correlated topological insulator. The $$^{239}$$Pu NMR spectra are consistent with axial symmetry of the shift tensor showing for the first time that $$^{239}$$Pu NMR can be observed in an anisotropic environment and up to room temperature. The temperature dependence of the $$^{239}$$Pu shift, combined with a relatively long spin-lattice relaxation time ($$T_1$$), indicate that PuB$$_4$$ adopts a nonmagnetic state with gaplike behavior consistent with our density functional theory calculations. The temperature dependencies of the NMR Knight shift and $$T^{-1}$$ imply bulk gaplike behavior confirming that PuB$$_4$$ is a good candidate topological insulator.

Journal Articles

Anisotropy of spin fluctuations in a tetragonal heavy fermion antiferromagnet CeRhAl$$_4$$Si$$_2$$

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

 Times Cited Count:1 Percentile:51

$$^{27}$$Al NMR experiments have been performed using a single crystal of CeRhAl$$_4$$Si$$_2$$. 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$$f$$ electrons behave as local moments in the high temperatures. From the NMR spectral analyses, the antiferromagnetic structures are discussed.

Journal Articles

Local moments in the heterogeneous electronic state of Cd-substituted CeCoIn$$_5$$; NQR relaxation rates

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

 Times Cited Count:2 Percentile:56.35

We have used nuclear quadrupole resonance (NQR) to probe microscopically the response of a prototypical quantum critical metal CeCoIn$$_5$$ 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 $$1/T_1$$. To reaffirm that localized $$f$$ moments are induced around the Cd substituents, we find a Gaussian spin-echo decay rate $$1/T_{rm 2G}$$ of transverse nuclear spin relaxation. Further, $$T_1T/T_{rm 2G}^2$$ 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 $$T^{0.7}$$-dependence. The latter temperature dependence is close to 0.75 in pure CeCoIn$$_5$$ and indicates that the bulk electronic state is located close to a two dimensional quantum critical instability.

Journal Articles

Observation of temperature-gradient-induced magnetization

Hou, D.*; Qiu, Z.*; Iguchi, Ryo*; Sato, Koji*; Vehstedt, E. K.*; Uchida, Kenichi*; Bauer, G. E. W.*; Saito, Eiji

Nature Communications (Internet), 7, p.12265_1 - 12265_6, 2016/07

 Times Cited Count:14 Percentile:64.01(Multidisciplinary Sciences)

Journal Articles

Incommensurate to commensurate antiferromagnetism in CeRhAl$$_4$$Si$$_2$$; An $$^{27}$$Al NMR study

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

 Times Cited Count:2 Percentile:11.15(Materials Science, Multidisciplinary)

$$^{27}$$Al nuclear magnetic resonance (NMR) experiments have been performed on a single crystal of CeRhAl$$_4$$Si$$_2$$, which is an antiferromagnetic Kondo-lattice compound with successive antiferromagnetic transitions of $$T_{rm N1}$$=14 K and $$T_{rm N2}$$=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 $$T_{rm N2}$$, but an incommensurate modulation of antiferromagnetic moments is present in the antiferromagnetic state between $$T_{rm N1}$$ and $$T_{rm N2}$$. The spin-lattice relaxation rate suggests that the $$4f$$ electrons behave as local moments at temperatures above $$T_{rm N1}$$.

Journal Articles

Microscopic investigation of electronic inhomogeneity induced by substitutions in a quantum critical metal CeCoIn$$_5$$

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:18 Percentile:61.91(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$$_5$$ 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 $$1/T_1$$ that influence the NFL behavior. The effects found here illustrate the need for care in interpreting NFL properties determined by macroscopic measurements.

Journal Articles

Cluster-transfer reactions with radioactive beams; A Spectroscopic tool for neutron-rich nuclei

Bottoni, S.*; Leoni, S.*; Fornal, B.*; Raabe, R.*; Rusek, K.*; Benzoni, G.*; Bracco, A.*; Crespi, F. C. L.*; Morales, A. I.*; Bednarczyk, P.*; et al.

Physical Review C, 92(2), p.024322_1 - 024322_8, 2015/08

 Times Cited Count:19 Percentile:77.88(Physics, Nuclear)

Journal Articles

Emergent antiferromagnetism out of the "hidden-order" state in URu$$_2$$Si$$_2$$; High magnetic field nuclear magnetic resonance to 40 T

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

 Times Cited Count:7 Percentile:49.94(Physics, Multidisciplinary)

Very high field $$^{29}$$Si-NMR measurements using a fully $$^{29}$$Si-enriched URu$$_2$$Si$$_2$$ 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 $$^{29}$$Si shift, $$^{29}K_c$$. Moreover, a strong enhancement of $$^{29}K_c$$ develops near a critical field $$H_{rm c}simeq 35.6$$ T, and the $$^{29}$$Si-NMR signal disappears suddenly at $$H_{rm c}$$, indicating the total suppression of the HO state. Nevertheless, a weak and shifted $$^{29}$$Si-NMR signal reappears for fields higher than $$H_{rm c}$$ 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.

Journal Articles

Microscopic properties of the heavy-fermion superconductor PuCoIn$$_5$$ explored by nuclear quadrupole resonance

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

 Times Cited Count:6 Percentile:45.91(Physics, Multidisciplinary)

We report $$^{115}$$In nuclear quadrupolar resonance (NQR) measurements on the heavy-fermion superconductor PuCoIn$$_5$$, in the temperature range 0.29 K $$leq Tleq$$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 $$T_c$$ is revealed, in agreement with the prediction for composite pairing. The nuclear spin-lattice relaxation rate $$T_1^{-1}(T)$$ clearly signals a superconducting (SC) phase transition at $$T_c simeq $$ 2.3 K, with strong spin fluctuations, mostly in-plane, dominating the relaxation process in the normal state near to $$T_c$$. Analysis of the $$T_1^{-1}$$ data in the SC state suggests that PuCoIn$$_5$$ is a strong-coupling $$d$$-wave superconductor.

Journal Articles

Coexistence of antiferromagnetism with superconductivity in CePt$$_2$$In$$_7$$; Microscopic phase diagram determined by $$^{115}$$In NMR and NQR

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

 Times Cited Count:14 Percentile:66.56(Physics, Multidisciplinary)

Single crystals of the heavy-fermion antiferromagnet CePt$$_{2}$$In$$_{7}$$ with a N$'e$el temperature ($$T_{N}$$) of 5.2 K at ambient pressure have been investigated by zero-field $$^{115}$$In-nuclear magnetic/quadrupole resonance (NMR/NQR) measurements as a function of applied pressure. Within the antiferromagnetic state the character of Ce's $$4f$$ electron appears to change from localized to itinerant-like at $$P^astsim2.4$$ GPa, approximately the pressure where superconductivity first emerges. With increased pressure, the superconducting transition $$T_{c}$$ reaches a maximum just at or slighty before antiferromagnetic order disappears, and not at the pressure $$P_{c}sim 3.4$$ GPa where the steeply decreasing N$'e$el boundary extrapolates to zero temperature. For $$P>P_{c}$$, the spin relaxation rate drops sharply by more than two orders of magnitude at $$T_{c}$$, suggestive of a first order transition.

Journal Articles

Weak itinerant antiferromagnetism in PuIn$$_3$$ explored using $$^{115}$$In nuclear quadrupole resonance

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

 Times Cited Count:5 Percentile:24.68(Physics, Condensed Matter)

The results of $$^{115}$$In nuclear quadrupole resonance (NQR) measurements on PuIn$$_3$$ are reported. Three of the four NQR lines of $$^{115}$$In expected for nuclear spin $$I$$=9/2 are observed. The equal spacing of these lines at 20 K yields the NQR frequency of $$nu_{rm Q}$$=10.45 MHz, and the asymmetry parameter of the electric field gradient, $$eta$$=0. The NQR line profile and the nuclear spin-lattice relaxation rate $$1/T_1$$ 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 $$M_{rm Q}(T)$$, extracted from the NQR spectra, and $$1/T_1$$ below $$T_{rm N}$$=14 K are well explained by the self-consistent renormalization (SCR) theory for spin fluctuations. In addition, scaling between $$T_1T$$ and $$M_{rm Q}(T)/M_{rm Q}(0)$$ is also consistent with the predictions of SCR theory, providing further evidence that PuIn$$_3$$ 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.

Journal Articles

Shubnikov-de Haas oscillation in PuIn$$_3$$

Haga, Yoshinori; Bauer, E. D.*; Tobash, P. H.*; Mitchell, J. N.*; Ayala-Valenzuela, O.*; McDonald, R. D.*; Mielke, C. H.*; Fisk, Z.

Journal of the Korean Physical Society, 63(3), p.380 - 382, 2013/08

 Times Cited Count:3 Percentile:27.8(Physics, Multidisciplinary)

Journal Articles

Quantitative study of the spin Hall magnetoresistance in ferromagnetic insulator/normal metal hybrids

Althammer, M.*; Meyer, S.*; Nakayama, Hiroyasu*; Schreier, M.*; Altmannshofer, S.*; Weiler, M.*; Huebl, H.*; Gepr$"a$gs, S.*; Opel, M.*; Gross, R.*; et al.

Physical Review B, 87(22), p.224401_1 - 224401_15, 2013/06

 Times Cited Count:399 Percentile:99.41(Materials Science, Multidisciplinary)

We experimentally investigate and quantitatively analyze the spin Hall magnetoresistance (SMR) effect in ferromagnetic insulator (FI)/Pt and FI/nonmagnetic metal/Pt hybrid structures. For the FI, we use either YIG, nickel ferrite, or magnetite and for the nonmagnet, Cu or Au. The SMR is theoretically ascribed to the combined action of spin Hall and inverse spin Hall effect in the Pt top layer. It therefore should characteristically depend upon the orientation of the magnetization in the adjacent ferromagnet and prevail even if an additional, nonmagnetic metal layer is inserted between Pt and the ferromagnet. Our experimental data corroborate these theoretical conjectures. Using the SMR theory to analyze our data, we extract the spin Hall angle and the spin diffusion length in Pt. For a spin-mixing conductance of $$4times 10^{14}Omega^{-1}$$m$$^{-2}$$, we obtain a spin Hall angle of 0.11 $$pm$$ 0.08 and a spin diffusion length of (1.5 $$pm$$ 0.5) nm for Pt in our samples.

Journal Articles

NMR/NQR Study of pressure-induced superconductor CePt$$_2$$In$$_7$$

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

 Times Cited Count:4 Percentile:80.22

Zero-field $$^{115}$$In-nuclear magnetic resonance (NMR) has been used to study single crystals of CePt$$_2$$In$$_7$$, a heavy-fermion antiferromagnet with a N$'e$el temperature ($$T_{rm N}$$) of 5.2 K at ambient pressure. The NMR spectra under zero field near the 3$$nu_{rm Q}$$ 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 ($$1/T_1$$) under pressures.

Journal Articles

Anisotropic spin fluctuations in the heavy fermion systems; Case studies of CePd$$_5$$Al$$_2$$ and NpPd$$_5$$Al$$_2$$

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

 Times Cited Count:7 Percentile:47.37(Physics, Multidisciplinary)

In the so-called 115 family members with chemical formulae of Ce$$T$$In$$_5$$ ($$T$$=Co, Rh, Ir) and $$An$$$$T$$Ga$$_5$$ ($$An$$=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 $$d$$-wave superconductivity with higher $$T_c$$. In order to examine this working hypothesis, the anisotropy ratios of antiferromagnetic fluctuations are derived from our NMR results for the superconductor NpPd$$_5$$Al$$_2$$ and antiferromagnet CePd$$_5$$Al$$_2$$, which are tetragonal compounds with a 115-related structure. CePd$$_5$$Al$$_2$$ shows Ising-type anisotropy, which is the same anisotropy as in the ordered state. On the other hand, NpPd$$_5$$Al$$_2$$ shows XY-type anisotropy just above $$T_c$$.

Journal Articles

NMR study for $$4f$$-localized ferromagnet CeRu$$_2$$Ga$$_2$$B

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

 Times Cited Count:10 Percentile:42.01(Materials Science, Multidisciplinary)

Nuclear magnetic resonance (NMR) studies using $$^{11}$$B and $$^{69,71}$$Ga have been performed on the tetragonal Ce-based ferromagnet CeRu$$_2$$Ga$$_2$$B. The Knight shifts for the nuclei show an Ising-type anisotropy along the $$c$$ 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 $$1/T_1$$ indicates that the anisotropy of spin fluctuations are also Ising-like along the $$c$$ axis. The localized character of the $$4f$$ electrons in this system is discussed.

Journal Articles

Observation of $$^{239}$$Pu nuclear magnetic resonance

Yasuoka, Hiroshi; Koutroulakis, G.*; Chudo, Hiroyuki; Richmond, S.*; Veirs, D. K.*; Smith, A. I.*; Bauer, E. D.*; Thompson, J. D.*; Jarvinen, G. D.*; Clark, D. L.*

Science, 336(6083), p.901 - 904, 2012/05

 Times Cited Count:46 Percentile:85.96(Multidisciplinary Sciences)

Journal Articles

CeRu$$_2$$Al$$_2$$B; A Local-moment 4$$f$$ magnet with a complex $$T$$-$$H$$ phase diagram

Raumbach, 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:29 Percentile:74.57(Materials Science, Multidisciplinary)

Journal Articles

CAF$'E$ experiments on the flow and freezing of metal fuel and cladding melts, 1; Test conditions and overview of the results

Fukano, Yoshitaka; Kawada, Kenichi; Sato, Ikken; Wright, A. E.*; Kilsdonk, D. J.*; Aeschlimann, R. W.*; Bauer, T. H.*

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles (FR 2009) (CD-ROM), 10 Pages, 2012/00

74 (Records 1-20 displayed on this page)