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Journal Articles

Slow electronic dynamics in the paramagnetic state of UTe$$_2$$

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Haga, Yoshinori; Tokiwa, Yoshifumi; Opletal, P.; Fujibayashi, Hiroyuki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; et al.

Journal of the Physical Society of Japan, 91(2), p.023707_1 - 023707_5, 2022/02

$$^{125}$$Te NMR experiments in field ($$H$$) applied along the easy magnetization axis (the $$a$$-axis) revealed slow electronic dynamics developing in the paramagnetic state of UTe$$_2$$. The observed slow fluctuations are concerned with a successive growth of long-range electronic correlations below 30$$-$$40 K, where the spin susceptibility along the hard magnetization axis (the $$b$$-axis) shows a broad maximum. The experiments also imply that tiny amounts of disorder or defects locally disturb the long-range electronic correlations and develop an inhomogeneous electronic state at low temperatures, leading to a low temperature upturn observed in the bulk-susceptibility in $$H|a$$. We suggest that UTe$$_2$$ would be located on the paramagnetic side near an electronic phase boundary, where either the magnetic or Fermi-surface instability would be the origin of the characteristic fluctuations.

Journal Articles

Single-crystal growth and magnetic phase diagram of the enantiopure crystal of NdPt$$_2$$B

Sato, Yoshiki*; Honda, Fuminori*; Maurya, A.*; Shimizu, Yusei*; Nakamura, Ai*; Homma, Yoshiya*; Li, D.*; Haga, Yoshinori; Aoki, Dai*

Physical Review Materials (Internet), 5(3), p.034411_1 - 034411_9, 2021/03

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

Journal Articles

$$^{125}$$Te-NMR study on a single crystal of heavy fermion superconductor UTe$$_2$$

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Hattori, Taisuke; Higa, Nonoka; Nakamine, Genki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Nakamura, Ai*; Shimizu, Yusei*; et al.

Journal of the Physical Society of Japan, 88(7), p.073701_1 - 073701_4, 2019/07

 Times Cited Count:29 Percentile:95.25(Physics, Multidisciplinary)

We report $$^{125}$$Te-NMR studies on a newly discovered heavy fermion superconductor UTe$$_2$$. Using a single crystal, we have measured the $$^{125}$$Te-NMR Knight shift $$K$$ and spin-lattice relaxation rate $$1/T_1$$ for fields along the three orthorhombic crystal axes. The data confirm a moderate Ising anisotropy for both the static ($$K$$) and dynamical susceptibilities ($$1/T_1$$) in the paramagnetic state above about 20 K. Around 20 K, however, we have observed a sudden loss of NMR spin-echo signal due to sudden enhancement of the NMR spin-spin relaxation rate $$1/T_2$$, when the field is applied along the easy axis of magnetization (=$$a$$ axis). This behavior suggests the development of longitudinal magnetic fluctuations along the $$a$$ axis at very low frequencies below 20 K.

Journal Articles

Magnetic and electrical properties of the ternary compound U$$_2$$Ir$$_3$$Si$$_5$$ with one-dimensional uranium zigzag chains

Li, D. X.*; Honda, Fuminori*; Miyake, Atsushi*; Homma, Yoshiya*; Haga, Yoshinori; Nakamura, Ai*; Shimizu, Yusei*; Maurya, A.*; Sato, Yoshiki*; Tokunaga, Masashi*; et al.

Physical Review B, 99(5), p.054408_1 - 054408_9, 2019/02

 Times Cited Count:2 Percentile:22.92(Materials Science, Multidisciplinary)

Journal Articles

Magnetization study on the Ising ferromagnet URhGe with high-precision angle-resolved magnetic field near the hard axis

Nakamura, Shota*; Sakakibara, Toshiro*; Shimizu, Yusei*; Kittaka, Shunichiro*; Kono, Yohei*; Haga, Yoshinori; Pospisil, J.; Yamamoto, Etsuji

Progress in Nuclear Science and Technology (Internet), 5, p.123 - 127, 2018/11

Journal Articles

Easy-plane XY spin fluctuations in the cycloidal magnet UPtGe studied via field orientation-dependent $$^{195}$$Pt NMR

Tokunaga, Yo; Nakamura, Ai*; Aoki, Dai*; Shimizu, Yusei*; Homma, Yoshiya*; Honda, Fuminori*; Sakai, Hironori; Hattori, Taisuke; Kambe, Shinsaku

Physical Review B, 98(1), p.014425_1 - 014425_5, 2018/07

 Times Cited Count:1 Percentile:8.26(Materials Science, Multidisciplinary)

$$^{195}$$Pt NMR measurements have been performed on a single crystal of the uranium-based compound UPtGe, which is the only 5f system known to possess an incommensurate helical (cycloidal) structure below TN = 50 K. Knight shift measurement confirmed the isotropic character of the static spin susceptibilities in hexagonal-like ac crystal planes of the EuAuGe-type crystal structure. The hyperfine coupling constants were also found to be isotropic in the planes. Nuclear relaxation rate measurement revealed the development of the antiferro-magnetic spin fluctuations with XY character confined to the hexagonal-like plane below 200 K. The results present a clear contrast to the Ising anisotropy of the fluctuations in ferromagnetic superconductors UCoGe and URhGe.

Journal Articles

Evidence for chiral $$d$$-wave superconductivity in URu$$_2$$Si$$_2$$ from the field-angle variation of its specific heat

Kittaka, Shunichiro*; Shimizu, Yusei*; Sakakibara, Toshiro*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika; Tsutsumi, Yasumasa*; Nomoto, Takuya*; Ikeda, Hiroaki*; Machida, Kazushige*

Journal of the Physical Society of Japan, 85(3), p.033704_1 - 033704_4, 2016/03

 Times Cited Count:25 Percentile:84.59(Physics, Multidisciplinary)

Journal Articles

Magnetic anisotropy and thermodynamic anomaly in the superconducting mixed state of UBe$$_{13}$$ probed by static dc magnetization measurements

Shimizu, Yusei*; Haga, Yoshinori; Yanagisawa, Tatsuya*; Amitsuka, Hiroshi*

Physical Review B, 93(2), p.024502_1 - 024502_8, 2016/01

 Times Cited Count:7 Percentile:41.71(Materials Science, Multidisciplinary)

Journal Articles

Field-orientation dependence of low-energy quasiparticle excitations in the heavy-electron superconductor UBe$$_{13}$$

Shimizu, Yusei*; Kittaka, Shunichiro*; Sakakibara, Toshiro*; Haga, Yoshinori; Yamamoto, Etsuji; Amitsuka, Hiroshi*; Tsutsumi, Yasumasa*; Machida, Kazushige*

Physical Review Letters, 114(14), p.147002_1 - 147002_6, 2015/04

 Times Cited Count:26 Percentile:83.91(Physics, Multidisciplinary)

Journal Articles

DC magnetization study on heavy-electron superconductor UBe$$_{13}$$

Shimizu, Yusei*; Haga, Yoshinori; Yanagisawa, Tatsuya*; Amitsuka, Hiroshi*; Aoki, Dai*; Brison, J.-P.*; Braithwaite, D.*

JPS Conference Proceedings (Internet), 3, p.015009_1 - 015009_6, 2014/06

Journal Articles

Observation of an unusual magnetic anomaly in the superconducting mixed state of heavy-fermion compound UBe$$_{13}$$ by precise dc magnetization measurements

Shimizu, Yusei*; Haga, Yoshinori; Ikeda, Yoichi*; Yanagisawa, Tatsuya*; Amitsuka, Hiroshi*

Physical Review Letters, 109(21), p.217001_1 - 217001_5, 2012/11

 Times Cited Count:15 Percentile:67.65(Physics, Multidisciplinary)

Journal Articles

Maki parameter and upper critical field of the heavy-fermion superconductor UBe$$_{13}$$

Shimizu, Yusei*; Ikeda, Yoichi*; Wakabayashi, Takumi*; Haga, Yoshinori; Tenya, Kenichi*; Hidaka, Hiroyuki*; Yanagisawa, Tatsuya*; Amitsuka, Hiroshi*

Journal of the Physical Society of Japan, 80(9), p.093701_1 - 093701_4, 2011/09

 Times Cited Count:7 Percentile:50.11(Physics, Multidisciplinary)

Journal Articles

Specific heat and magnetization studies of the superconducting mixed state of UBe$$_{13}$$

Shimizu, Yusei*; Ikeda, Yoichi*; Wakabayashi, Takumi*; Tenya, Kenichi*; Haga, Yoshinori; Hidaka, Hiroyuki*; Yanagisawa, Tatsuya*; Amitsuka, Hiroshi*

Journal of the Physical Society of Japan, 80(Suppl.A), p.SA100_1 - SA100_3, 2011/07

 Times Cited Count:1 Percentile:12.07(Physics, Multidisciplinary)

Journal Articles

Magnetization in the superconducting mixed state of the heavy-fermion compound UBe$$_{13}$$

Shimizu, Yusei*; Ikeda, Yoichi*; Wakabayashi, Takumi*; Tenya, Kenichi*; Haga, Yoshinori; Hidaka, Hiroyuki*; Yanagisawa, Tatsuya*; Amitsuka, Hiroshi*

Journal of Physics; Conference Series, 273, p.012084_1 - 012084_4, 2011/02

 Times Cited Count:3 Percentile:66.37

Oral presentation

Pt-NMR study on UPtGe

Tokunaga, Yo; Nakamura, Ai*; Aoki, Dai*; Hattori, Taisuke; Sakai, Hironori; Kambe, Shinsaku; Honda, Fuminori*; Homma, Yoshiya*; Li, D.*; Shimizu, Yusei*

no journal, , 

Uranium (U) based heavy fermion compounds, UGe$$_2$$, UCoGe, and URhGe are the only fully established examples of ferromagnetic superconductors in which uniform superconductivity exists deep inside of the FM state. UPtGe has the same crystal structure with URhGe and UCoGe and shows an antiferromagnetic ordering below $$T_N$$ = 51 K where the ordered moments of U-moments are 1.1$$sim$$1.4$$mu_B$$. We will present the result of our new Pt-NMR study on this compound and discuss the anisotropy of the spin fluctuations in UCoGe, URhGe and UPtGe.

Oral presentation

Sn-NMR study of successive phase transition in URhSn

Tokunaga, Yo; Shimizu, Yusei*; Maurya, A.*; Honda, Fuminori*; Nakamura, Ai*; Sato, Yoshiki*; Li, D.*; Homma, Yoshiya*; Aoki, Dai*; Higa, Nonoka; et al.

no journal, , 

Uranium-based compound URhS exhibits two successive phase transitions at 54 K and 18 K. The origin of the phase transition at 18 K has been known to be ferromagnetic ordering, while the origin of the transition at 54 K is still unknown. In this study, we have investigated the mechanism of the successive phase transitions in URhSn by using Sn-NMR.

Oral presentation

$$^{125}$$Te-NMR study of magnetic fluctuations in a newly discovered uranium-based superconductor UTe$$_2$$

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Hattori, Taisuke; Higa, Nonoka*; Nakamine, Genki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Nakamura, Ai*; Shimizu, Yusei*; et al.

no journal, , 

$$^{125}$$Te NMR studies have been performed on a newly discovered heavy fermion superconductor UTe$$_2$$.Using a single crystal, we have measured the $$^{125}$$Te NMR Knight shift $$K$$ and spin-lattice relaxation rate $$1/T_1$$ for fields along the three orthorhombic crystal axes. The data confirm a moderate Ising anisotropy for both the static ($$K$$) and dynamical susceptibilities ($$1/T_1$$) in the paramagnetic state above about 20 K. Around 20 K, however, we have observed a sudden loss of NMR spin-echo signal due to sudden enhancement of the NMR spin-spin relaxation rate $$1/T_2$$, when the field is applied along the easy axis of magnetization (=$$a$$ axis).

Oral presentation

NMR study of magnetic spin fluctuations in UTe$$_2$$

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Hattori, Taisuke; Higa, Nonoka*; Nakamine, Genki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Nakamura, Ai*; Shimizu, Yusei*; et al.

no journal, , 

Recently, Ran et al. reported evidence for superconductivity in the uranium-based heavy fermion material UTe$$_2$$, exhibiting the rather high transition temperature of 1.6 K. The ground state of UTe$$_2$$ is paramagnetic, not ferromagnetic. However, the compound still exhibits a very large and anisotropic upper critical field H$$_{c2}$$, exceeding the Pauli limit along the three principal axes, similar to the ferromagnetic superconductors, UCoGe and URhGe. Field-induced metamagnetic transition and re-entrant superconducting behaviour have been reported under strong magnetic fields around 35 T, when a magnetic field was applied along the orthorhombic hard-magnetization b-axis. In this study, we have performed Te-NMR measurements on a newly discovered heavy fermion superconductor UTe$$_2$$. Our NMR data confirm a moderate Ising anisotropy for both the static (K) and dynamical susceptibilities (1/$$T_1$$) in the paramagnetic state above about 20 K.

Oral presentation

Electronic fluctuations in the normal state of UTe$$_2$$

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Opletal, P.; Tokiwa, Yoshifumi; Haga, Yoshinori; Fujibayashi, Hiroyuki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; et al.

no journal, , 

We report the results of $$^{125}$$Te NMR measurements in field ($$H$$) applied along the easy magnetization axis (the $$a$$-axis). The experiments revealed slow electronic dynamics developing in the paramagnetic state of UTe$$_2$$. The observed slow fluctuations are concerned with a successive growth of long-range electronic correlations below 30$$-$$40 K, where the spin susceptibility along the hard magnetization axis (the $$b$$-axis) shows a broad maximum. The experiments also imply that tiny amounts of disorder or defects locally disturb the long-range electronic correlations and develop an inhomogeneous electronic state at low temperatures, leading to a low temperature upturn observed in the bulk-susceptibility in $$H|a$$.

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