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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.
RhGa explored by 
Ga nuclear quadrupole resonanceYamamoto, Shingo*; Fujii, Takuto*; Luther, S.*; Yasuoka, Hiroshi*; Sakai, Hironori; B
rtl, F.*; Ranjith, K. M.*; Rosner, H.*; Wosnitza, J.*; Strydom, A. M.*; et al.
Physical Review B, 106(11), p.115125_1 - 115125_5, 2022/09
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)We have studied the microscopic magnetic properties, the nature of the 130 K phase transition, and the ground state in the recently synthesized compound CeRhGa by use of Ga nuclear quadrupole resonance (NQR). The NQR spectra clearly show an unusual phase transition at 
K, yielding a splitting of the high-temperature single NQR line into two well-resolved NQR lines, providing evidence for two crystallographically inequivalent Ga sites. The NQR frequencies are in good agreement with fully relativistic calculations of the band structure. Our NQR results indicate the absence of magnetic or charge order down to 0.3 K. The temperature dependence of the spin-lattice relaxation rate shows three distinct regimes, with onset temperatures at 
and 2 K. The temperature-independent , observed between and 2 K, crosses over to a Korringa process, 
, below 
2 K, which evidences a rare two-ion Kondo scenario: The system evolves into a dense Kondo coherent state below 2.0 and 0.8 K probed by the two different Ga sites.
; 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.
Ga in unconventional superconductor PuRhGa
Sakai, Hironori; Tokunaga, Yo; Fujimoto, Tatsuya; Kambe, Shinsaku; Walstedt, R. E.; Yasuoka, Hiroshi; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji; Nakamura, Akio; et al.
Journal of the Physical Society of Japan, 75(Suppl.), p.50 - 52, 2006/08
Very recently, we have succeeded in NMR/NQR measurements for PuRhGa. PuRhGa is a superconductor with 
9 K, which is isomorphic to PuCoGa with the higher =18 K. We have reported that PuRhGa is an unconventional superconductor with an anisotropic gap, through the measurement of NQR spin-lattice relaxation rate 
, while PuCoGa is also reported to be such an anisotropic superconductor. The Knight shift 
and of NMR under applied field for the normal state of PuRhGa suggest an anisotropic feature of hyperfine and/or spin fluctuation in this system. We will outline the superconducting state and report the nature of the normal state based on the basis of and 
results. The difference between PuRhGa and PuCoGa will be also discussed.
; Ga NMR/NQR studySakai, Hironori; Tokunaga, Yo; Fujimoto, Tatsuya; Kambe, Shinsaku; Walstedt, R. E.; Yasuoka, Hiroshi; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji; Nakamura, Akio; et al.
Physica B; Condensed Matter, 378-380, p.1005 - 1006, 2006/05
Times Cited Count：6 Percentile：31.23(Physics, Condensed Matter) Ga NMR/NQR studies have been performed on a single crystal of the transuranium superconductor PuRhGa with =9 K. The spin-lattice relaxation rate reveals that PuRhGa is an unconventional superconductor having an anisotropic superconducting gap. Moreover, Korringa behavior (
) is observed in the normal state below 30 K. This result suggests that the superconductivity sets in after the formation of a Fermi liquid state in this compound.
; Ga NQR study on a single crystalSakai, Hironori; Tokunaga, Yo; Fujimoto, Tatsuya; Kambe, Shinsaku; Walstedt, R. E.; Yasuoka, Hiroshi; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji; Nakamura, Akio; et al.
Journal of the Physical Society of Japan, 74(6), p.1710 - 1713, 2005/06
Times Cited Count：78 Percentile：90.09(Physics, Multidisciplinary)Ga NMR/NQR studies have been performed on a single crystal of the transuranium superconductor PuRhGa with 
K. We have observed a Ga NQR line at 29.15 MHz, and assigned it to the 
Ga site using the NMR results. The Ga NQR spin-lattice relaxation rate shows no coherence peak just below , but obeys 
behavior below . This result strongly suggests that PuRhGa is an unconventional superconductor having an anisotropic superconducting gap. The gap amplitude 2
and the residual density of states 
0.25 have been determined assuming a simple polar function of the form 
=
, where 
and 
are angular parameters on the Fermi surface.
Kato, Harukazu; Sakai, Hironori; Kambe, Shinsaku; Walstedt, R. E.; Tokiwa, Yoshifumi; Onuki, Yoshichika
Acta Physica Polonica B, 34(2), p.1063 - 1066, 2003/09
We performed Ga-NMR/NQR studies for UPtGa, which is a 5
-itinerant antiferromagnets with Neel temperature 
= 26 K and an electronic specific coefficient 
= 57 mJ/mol K
. From the NMR spectrum in the paramagnetic temperature region, the hyperfine coupling constants 
in the paramagnetic state have been evaluated. The magnitude of the transferred field has been evaluated from the zero-applied-field spectrum, yielding a value for the hyperfine coupling constant 
in the antiferromagnetic state. The estimated value of is an order of magnitude larger than that of . This implies the existence of a long-ranged hyperfine interaction path. The mechanism of the hyperfine interaction will be discussed in terms of RKKY interactions.
Kato, Harukazu; Sakai, Hironori; Tokiwa, Yoshifumi; Kambe, Shinsaku; Walstedt, R. E.; Onuki, Yoshichika
Journal of Physics and Chemistry of Solids, 63(6-8), p.1197 - 1200, 2002/06
Times Cited Count：11 Percentile：50.72(Chemistry, Multidisciplinary)no abstracts in English
Ikushima, Kenji; Aoki, Dai*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika
Journal of Magnetism and Magnetic Materials, 226-230(Part.1), p.89 - 91, 2001/05
no abstracts in English
observed by Ga NQRIkushima, Kenji; Aoki, Dai*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika; Kambe, Shinsaku; Walstedt, R. E.
Journal of the Physical Society of Japan, Vol.70, Supplement A, p.31 - 33, 2001/05
no abstracts in English
Yasuoka, Hiroshi
Journal of the Physical Society of Japan, 69(suppl.B), p.161 - 172, 2000/00
no abstracts in English
Ikushima, Kenji; Yasuoka, Hiroshi; Uwatoko, Yoshiya*; Ishikawa, Yoshikazu*
Physical Review B, 60(21), p.14537 - 14540, 1999/00
Times Cited Count：5 Percentile：33.75(Materials Science, Multidisciplinary)no abstracts in English
by exampleSakai, Hironori
no journal, ,
In the heavy fermion superconductor CeCoIn, dilute substitutions by Sn or Cd suppress the superconductivity or induce an antiferromagnetically ordered state. Such impurity effects have been microscopically investigated by nuclear quadrupole resonance (NQR) technique. While the Sn substituents weaken electronic correlations and suppress the superconductivity, the Cd substituents induce local moments closely around themselves but the bulk electronic state far from the substituents stays as in a pure CeCoIn. Such a heterogeneous electronic state in the Cd substituted system means a local breakage of Kondo hybridization by non-magnetic Cd substituents.
; Around Kondo holesSakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Yokoyama, Makoto*; Zhu, J.-X.*; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*
no journal, ,
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 or Zn for In. Such non-magnetic Cd or Zn substitutions induce a long range antiferromagnetism. In the case of the Cd substitutions, approximately half of the Cd substituents induce local Ce moments in their close proximity, as observed by site-dependent longitudinal nuclear spin relaxation rates . In the case of Zn substitutions, the similar site dependence of is observed as well. We will discuss about the heterogeneous electronic state realized in such a dilutely substituted system.
Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Ronning, F.*; Zhu, J.-X.*; Suzuki, Kohei*; Oshima, Yoshiki*; Yokoyama, Makoto*
no journal, ,
Dilute substitutions of non-magnetic dopants Zn can induce a long-ranged antiferromagnetic ordering to a heavy fermion superconductor CeCoIn. We have microscopically investigated the Zn-doped CeCoIn by means of the nuclear quadrupole/magnetic resonance (NQR/NMR) techniques.
Sakai, Hironori; Hattori, Taisuke; Higa, Nonoka; Tokunaga, Yo; Kambe, Shinsaku; Ronning, F.*; Zhu, J.-X.*; Suzuki, Kohei*; Oshima, Yoshiki*; Yokoyama, Makoto*
no journal, ,
We have used Nuclear Quadrupole Resonance (NQR) to probe microscopically the response of prototypical quantum critical metal CeCoIn to substitutions of small amounts of Cd or Zn for In. Such non-magnetic Cd or Zn substitutions induce a long range antiferromagnetism. In the case of Cd substitutions, approximately half of the Cd substituents induce local Ce moments in their close proximity, as observed by site-dependent longitudinal nuclear spin relaxation rates . In the paramagnetic state, the values of at the main peak position are similar to those in the pure CeCoIn, while those are enhanced at the skirt position of spectrum. We will discuss about the heterogeneous electronic state realized in such a Zn substituted system and discuss about the coexistence of superconductivity with the antiferromagnetism, as well.
Sakai, Hironori
no journal, ,
We have performed NMR/NQR experiments for slightly substituted CeCoIn by several substituents of Cd, Zn and Ni. In this presentation, the microscopic electronic states will be discussed.
Sakai, Hironori; Tokunaga, Yo; Haga, Yoshinori; Kambe, Shinsaku; Ronning, F.*; Zhu, J.-X.*; Thompson, J. D.*; Kotegawa, Hisashi*; To, Hideki*; Suzuki, Kohei*; et al.
no journal, ,
Heavy fermion superconductor CeCoIn is considered as a quantum critical antiferromagnetic material. When the In elements are slightly substituted by Zn elements, a long-range antiferromagnetism is induced. On the other hand, slight Sn substitutions make the system step away from the quantum critical point. In the case of Zn substitutions, heterogeneity of antiferromagnetic area in the matrix of heavy fermion state has been microscopically confirmed by NQR measurements. In the case of Ni substitutions for the Co elements, the NQR result appears to be the same as in Sn substituted system.
