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Journal Articles

Lattice dynamics in FeSe via inelastic X-ray scattering and first-principles calculations

Murai, Naoki; Fukuda, Tatsuo; Nakajima, Masamichi*; Kawamura, Mitsuaki*; Ishikawa, Daisuke*; Tajima, Setsuko*; Baron, A. Q. R.*

Physical Review B, 101(3), p.035126_1 - 035126_6, 2020/01

 Times Cited Count:5 Percentile:41.49(Materials Science, Multidisciplinary)

We report an inelastic X-ray scattering investigation of phonons in FeSe superconductor. Comparing the experimental phonon dispersion with density functional theory (DFT) calculations in the non-magnetic state, we found a significant disagreement between them. A better overall agreement was obtained by allowing for spin-polarization in DFT calculations, despite the absence of magnetic order in FeSe. This calculation gives a realistic approximation, at DFT level, of the disordered paramagnetic state of FeSe, in which strong spin fluctuations are present.

Journal Articles

Effect of $$B$$-site randomness on the antiferroelectric/relaxor nature of the ground state; Diffuse and inelastic X-ray scattering study of Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_3$$

Owada, Kenji*; Tsukada, Shinya*; Fukuda, Tatsuo; Tsutsui, Satoshi*; Baron, A. Q. R.*; Mizuki, Junichiro*; Owa, Hidehiro*; Yasuda, Naohiko*; Terauchi, Hikaru*

Physical Review B, 98(5), p.054106_1 - 054106_10, 2018/08

 Times Cited Count:3 Percentile:17.66(Materials Science, Multidisciplinary)

Journal Articles

Impurity effects in the microscopic elastic properties of polycrystalline Mg-Zn-Y alloys with a synchronised long-period stacking ordered phase

Hosokawa, Shinya*; Kimura, Koji*; Yamasaki, Michiaki*; Kawamura, Yoshihito*; Yoshida, Koji*; Inui, Masanori*; Tsutsui, Satoshi*; Baron, A. Q. R.*; Kawakita, Yukinobu; Ito, Shinichi*

Journal of Alloys and Compounds, 695, p.426 - 432, 2017/02

 Times Cited Count:3 Percentile:18.5(Chemistry, Physical)

Journal Articles

Effect of magnetism on lattice dynamics in SrFe$$_2$$As$$_2$$ using high-resolution inelastic X-ray scattering

Murai, Naoki*; Fukuda, Tatsuo; Kobayashi, Tatsuya*; Nakajima, Masamichi*; Uchiyama, Hiroshi*; Ishikawa, Daisuke*; Tsutsui, Satoshi*; Nakamura, Hiroki; Machida, Masahiko; Miyasaka, Shigeki*; et al.

Physical Review B, 93(2), p.020301_1 - 020301_5, 2016/01

 Times Cited Count:7 Percentile:36.13(Materials Science, Multidisciplinary)

Journal Articles

Precise measurement of acoustic phonons in PrFeAsO$$_{1-y}$$

Fukuda, Tatsuo; Baron, A. Q. R.*; Uchiyama, Hiroshi*; Nakamura, Hiroki; Ishikado, Motoyuki*; Machida, Masahiko; Shamoto, Shinichi

SPring-8/SACLA Riyo Kenkyu Seikashu (Internet), 3(2), p.290 - 293, 2015/07

Journal Articles

Anharmonic Pr guest modes in Pr(Os$$_{1-x}$$Ru$$_x$$)$$_4$$Sb$$_{12}$$ investigated by inelastic X-ray scattering

Tsutsui, Satoshi; Kaneko, Koji; Miyazaki, Ryoichi*; Higashinaka, Ryuji*; Aoki, Yuji*; Kobayashi, Riki*; Wakimoto, Shuichi; Baron, A. Q. R.*; Sugawara, Hitoshi*; Sato, Hideyuki*

JPS Conference Proceedings (Internet), 3, p.011060_1 - 011060_5, 2014/06

Journal Articles

Multi-spin-state dynamics during insulator-metal crossover in LaCoO$$_3$$

Doi, Atsunori*; Fujioka, Jun*; Fukuda, Tatsuo; Tsutsui, Satoshi*; Okuyama, Daisuke*; Taguchi, Yasujiro*; Arima, Takahisa*; Baron, A. Q. R.*; Tokura, Yoshinori*

Physical Review B, 90(8), p.081109_1 - 081109_4, 2014/01

 Times Cited Count:17 Percentile:60.29(Materials Science, Multidisciplinary)

Journal Articles

Soft phonon mode coupled with antiferromagnetic order in incipient-ferroelectric Mott insulators Sr$$_{1-x}$$Ba$$_x$$MnO$$_3$$

Sakai, Hideaki*; Fujioka, Jun*; Fukuda, Tatsuo; Bahramy, M. S.*; Okuyama, Daisuke*; Arita, Ryotaro*; Arima, Takahisa*; Baron, A. Q. R.*; Taguchi, Yasujiro*; Tokura, Yoshinori*

Physical Review B, 86(10), p.104407_1 - 104407_11, 2012/09

 Times Cited Count:29 Percentile:74.97(Materials Science, Multidisciplinary)

Journal Articles

Emergent phenomena in perovskite-type manganites

Taguchi, Yasujiro*; Sakai, Hideaki*; Okuyama, Daisuke*; Ishiwata, Shintaro*; Fujioka, Jun*; Fukuda, Tatsuo; Hashizume, Daisuke*; Kagawa, Fumitaka*; Takahashi, Yoichiro*; Shimano, Ryo*; et al.

Physica B; Condensed Matter, 407(11), p.1685 - 1688, 2012/06

 Times Cited Count:5 Percentile:20.32(Physics, Condensed Matter)

Journal Articles

Effect of B-site randomness on the antiferroelectric/relaxor nature of the ground state; Inelastic X-ray scattering study of Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$

Owada, Kenji; Fukuda, Tatsuo; Mizuki, Junichiro; Hirota, Kazuma*; Terauchi, Hikaru*; Tsutsui, Satoshi*; Baron, A. Q. R.*; Owa, Hidehiro*; Yasuda, Naohiko*

Journal of the Korean Physical Society, 59(3), p.2509 - 2514, 2011/09

 Times Cited Count:2 Percentile:20.56(Physics, Multidisciplinary)

Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$ (PIN) can be antiferroelectric (AFE), ferroelectric (FE) or a relaxor depending upon the perovskite B-site randomness. Orderd PIN (O-PIN, without B-site randomness) is supposed to be an ideal system of lead-based complex perovskite Pb(B'B'')O$$_{3}$$ and expected to give us a clear picture of the AFE/relaxor nature of the ground state by the B-site randomness. We studied the dynamics of O-PIN by inelastic X-ray scattering. The quasielastic (QE) scattering shows the critical slowing down and the transverse acoustic (TA) mode shows the softening towards $$T_{rm N}$$. On the other hand, the transverse optic (TO) mode shows the softening toward low temperature with no clear anomaly at $$T_{rm N}$$. These results represent that the antiferroelectric (AFE) phase transition is associated with the TA and the origin of the QE scattering, while ferroelectric correlation does exist behind the AFE ordering. The effect of B-site randomness is finally discussed on the basis of the results.

Journal Articles

Soft and isotropic phonons in PrFeAsO$$_{1-y}$$

Fukuda, Tatsuo; Baron, A. Q. R.*; Nakamura, Hiroki; Shamoto, Shinichi; Ishikado, Motoyuki; Machida, Masahiko; Uchiyama, Hiroshi*; Iyo, Akira*; Kito, Hijiri*; Mizuki, Junichiro; et al.

Physical Review B, 84(6), p.064504_1 - 064504_13, 2011/08

 Times Cited Count:9 Percentile:40.24(Materials Science, Multidisciplinary)

Journal Articles

Phonon spectra of PrFeAsO$$_{1-y}$$ via inelastic X-ray scattering

Fukuda, Tatsuo; Baron, A. Q. R.*; Nakamura, Hiroki; Shamoto, Shinichi; Ishikado, Motoyuki; Machida, Masahiko; Uchiyama, Hiroshi*; Iyo, Akira*; Kito, Hijiri*; Mizuki, Junichiro; et al.

Journal of the Physical Society of Japan, 80(Suppl.B), p.SB015_1 - SB015_4, 2011/01

 Times Cited Count:1 Percentile:11.58(Physics, Multidisciplinary)

We have investigated phonons of PrFeAsO$$_{1-y}$$ using high-resolution inelastic X-ray scattering and $$ab-initio$$ calculations. Extensive measurements show that there are some changes in phonon spectra with temperature and/or doping. However, we compare our data with several calculations and find that the experimentally observed changes are much smaller than differences between the experiment. data and the calculations. Agreement is improved if magnetism is included in the calculations. However, still in disagreement even in the parent sample below T$$_N$$. We consider several modifications of the $$ab-initio$$ calculations. The best agreement is obtained from modifying the nonmagnetic calculation. by softening only the in-plane nearest-neighbor Fe-As force constant. Fluctuating magnetism may be a partial explanation for the failure of the calculations, but seems incomplete in the face of the similarity of the measured phonon response in all the systems investigated including those known to have static magnetism.

Journal Articles

Phonons in the new iron-based high-temperature superconductors

Fukuda, Tatsuo; Baron, A. Q. R.*

SPring-8 Research Frontiers 2008, p.90 - 91, 2009/09

no abstracts in English

Journal Articles

Unconventional ferroelectric transition in the multiferroic compound TbMnO$$_{3}$$ revealed by the absence of an anomaly in $$c$$-polarized phonon dispersion

Kajimoto, Ryoichi; Sagayama, Hajime*; Sasai, Kenzo*; Fukuda, Tatsuo; Tsutsui, Satoshi*; Arima, Takahisa*; Hirota, Kazuma*; Mitsui, Yukari*; Yoshizawa, Hideki*; Baron, A. Q. R.*; et al.

Physical Review Letters, 102(24), p.247602_1 - 247602_4, 2009/06

 Times Cited Count:12 Percentile:59.63(Physics, Multidisciplinary)

Journal Articles

Antiferroelectric correlation in relaxor Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$ and ferroelectric correlation in antiferroelectric Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$

Owada, Kenji; Hirota, Kazuma*; Terauchi, Hikaru*; Fukuda, Tatsuo; Tsutsui, Satoshi*; Baron, A. Q. R.*; Mizuki, Junichiro; Owa, Hidehiro*; Yasuda, Naohiko*

Transactions of the Materials Research Society of Japan, 34(1), p.19 - 22, 2009/03

Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$ (PIN) can be antiferroelectric (AFE), ferroelectric (FE) or a relaxor depending upon the perovskite B-site randomness. This is characterized by measurements of dielectric response, which shows behavior that is usually clearly in one of those three classes. In contrast, X-ray scattering studies suggest the presence of AFE correlation in the relaxor state and FE in AFE state. Weak phonon softening at zone boundary in relaxor state shows that the AFE correlation intrinsically exists in PIN, as does the corresponding elastic scattering at (${it h}$/2 ${it k}$/2 0), while weak diffuse scattering around 333 Bragg reflection appears in AFE state suggesting FE correlation. These results will support our previous speculation that the AFE and FE correlations coexist in PIN (K. Owada ${it et al}$., Phys, Rev. B${bf 77}$ 094136 (2008)). Such a coexistence or competition is widely seen in the perovskite relaxor and the coexistence of FE and AFE correlations is essential for generating relaxor state.

Journal Articles

Lattice dynamics of LaFeAsO$$_{1-x}$$F$$_x$$ and PrFeAsO$$_{1-y}$$ via inelastic X-ray scattering and first-principles calculation

Fukuda, Tatsuo; Baron, A. Q. R.*; Shamoto, Shinichi; Ishikado, Motoyuki; Nakamura, Hiroki; Machida, Masahiko; Uchiyama, Hiroshi*; Tsutsui, Satoshi*; Iyo, Akira*; Kito, Hijiri*; et al.

Journal of the Physical Society of Japan, 77(10), p.103715_1 - 103715_4, 2008/10

 Times Cited Count:41 Percentile:83.34(Physics, Multidisciplinary)

The lattice dynamics of LaFeAsO$$_{1-x}$$F$$_x$$ ($$x$$=0, 0.1) and PrFeAsO$$_{1-y}$$ ($$ysim$$0.1) are investigated using inelastic X-ray scattering. Measurements of powder samples provide an approximation to the phonon DOS, while dispersion is measured from a single crystal of PrFeAsO$$_{1-y}$$. A model that agrees reasonably well with all of the data at room temperature is built from results of ab-initio calculations by reducing the strength of the Fe-As bond by 30%.

Journal Articles

Intrinsic ferroelectric instability in Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$ revealed by changing B-site randomness; Inelastic X-ray scattering study

Owada, Kenji; Hirota, Kazuma*; Terauchi, Hikaru*; Fukuda, Tatsuo; Tsutsui, Satoshi*; Baron, A. Q. R.*; Mizuki, Junichiro; Owa, Hidehiro*; Yasuda, Naohiko*

Physical Review B, 77(9), p.094136_1 - 094136_8, 2008/03

 Times Cited Count:16 Percentile:57.29(Materials Science, Multidisciplinary)

Antiferroelectric (AFE), ferroelectric (FE) or relaxor states can appear in Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$ (PIN) depending upon the perovskite B-site randomness. We studied the effects of this randomness on the dynamics of PIN by high resolution inelastic X-ray scattering using ordered PIN (AFE) and disordered PIN (relaxor) single crystals. We have found a clear softening of a transverse optic mode at the $$Gamma$$ point in both the samples, indicating a robust and intrinsic ferroelectric instability regardless of the actual ground state. We interpret that AFE is stabilized only when In and Nb ions are spatially ordered enough to overwhelm the FE instability. As the B-site randomness becomes larger, AFE is suppressed and the hidden FE state starts appearing. Ultimately, the randomness begins to predominate over the development of FE regions and blocks a long range FE order, which we believe yields polar nanoregions resulting in relaxor behaviors.

Journal Articles

Lattice dynamics of the Zn-Mg-Sc icosahedral quasicrystal and its Zn-Sc periodic 1/1 approximant

de Boissieu, M.*; Francoual, S.*; Minalkovi$v{c}$, M.*; Shibata, Kaoru; Baron, A. Q. R.*; Sidis, Y.*; Ishimasa, Tsutomu*; Wu, D.*; Lograsso, T.*; Regnault, L.-P.*; et al.

Nature Materials, 6(12), p.977 - 984, 2007/12

 Times Cited Count:39 Percentile:80.45(Chemistry, Physical)

We have carried out inelastic X-ray and neutron scattering experiments on single-grain samples of the Zn-Mg-Sc icosahedral quasicrystal and of the Zn-Sc periodic cubic 1/1 approximant, with the aim of studying the respective influence of the local order and the long-range order (periodic or quasiperiodic) on lattice dynamics. Besides the overall similarities and the existence of a pseudo-gap in the transverse dispersion relation, marked difference are observed, the pseudo-gap being larger and better defined in the approximant than in the quasicrystal. These results are compared with simulations on atomic models and using oscillating pair potentials, and the simulations reproduce in detail the experimental results.

Journal Articles

Phonon softening in superconducting diamond

Hoesch, M.*; Fukuda, Tatsuo; Mizuki, Junichiro; Takenouchi, Tomohiro*; Kawarada, Hiroshi*; Sutter, J. P.*; Tsutsui, Satoshi*; Baron, A. Q. R.*; Nagao, Masanori*; Takano, Yoshihiko*

Physical Review B, 75(14), p.140508_1 - 140508_4, 2007/04

 Times Cited Count:35 Percentile:78.08(Materials Science, Multidisciplinary)

We observed phonon dispersions using inelastic X-ray scattering from CVD-grown high quality superconducting ($$T_c$$=4.2 K) boron-doped and non-doped diamonds. By comparing these two, we found almost no change in the acoustic branch along both [111] and [001] directions. On the other hand, strong softening were observed in the optical branch of the boron-doped diamond in both directions: about 2 meV at Brillouin zone boundary and 8 meV at zone center ($$Gamma$$ point). From this result we estimated the electron-phonon coupling factor $$lambda$$=0.33, and this supports theoretical models suggesting a phonon-mediated pairing mechanism via coupling of optical phonon modes to Fermi surfaces around the $$Gamma$$ point.

Journal Articles

Doping dependence of softening in the bond-stretching phonon mode of La$$_{2-x}$$Sr$$_x$$CuO$$_4$$ (0$$leq x leq$$0.29)

Fukuda, Tatsuo; Mizuki, Junichiro; Ikeuchi, Kazuhiko*; Yamada, Kazuyoshi*; Baron, A. Q. R.*; Tsutsui, Satoshi*

Physical Review B, 71(6), p.060501_1 - 060501_4, 2005/02

 Times Cited Count:57 Percentile:86.3(Materials Science, Multidisciplinary)

Phonons along the [100] direction, in particular the highest energy Cu-O bond-stretching LO mode, of La$$_{2-x}$$Sr$$_x$$CuO$$_4$$ have been studied by inelastic X-ray scattering experiments. The LO phonon mode in the $$x$$ = 0.12 sample shows significant softening similar to early neutron studies. We show here a recovery of the softening was found in the $$x$$ = 0.29 sample, where superconductivity degrades and normal metallic conductivity dominates. The results suggest one-to-one correspondence between the softening of this LO phonon and the superconductivity.

42 (Records 1-20 displayed on this page)