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Journal Articles

Magnetic field effect on Fe-induced short-range magnetic correlation and electrical conductivity in Bi$$_{1.75}$$Pb$$_{0.35}$$Sr$$_{1.90}$$Cu$$_{0.91}$$Fe$$_{0.09}$$O$$_{6+y}$$

Wakimoto, Shuichi; Hiraka, Haruhiro*; Kudo, Kazutaka*; Okamoto, Daichi*; Nishizaki, Terukazu*; Kakurai, Kazuhisa; Hong, T.*; Zheludev, A.*; Tranquada, J. M.*; Kobayashi, Norio*; et al.

Physical Review B, 82(6), p.064507_1 - 064507_7, 2010/08

 Times Cited Count:7 Percentile:36.48(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Incommensurate spin correlations induced by magnetic Fe ions substituted into overdoped Bi$$_{1.75}$$Pb$$_{0.35}$$Sr$$_{1.90}$$CuO$$_{6+z}$$

Hiraka, Haruhiro*; Hayashi, Yoichiro*; Wakimoto, Shuichi; Takeda, Masayasu; Kakurai, Kazuhisa; Adachi, Tadashi*; Koike, Yoji*; Yamada, Ikuya*; Miyazaki, Masanori*; Hiraishi, Masatoshi*; et al.

Physical Review B, 81(14), p.144501_1 - 144501_6, 2010/04

 Times Cited Count:15 Percentile:57.93(Materials Science, Multidisciplinary)

Journal Articles

Magnetic dispersion of the diagonal incommensurate phase in lightly doped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$

Matsuda, Masaaki; Fujita, Masaki*; Wakimoto, Shuichi; Fernandez-Baca, J. A.*; Tranquada, J. M.*; Yamada, Kazuyoshi*

Physical Review Letters, 101(19), p.197001_1 - 197001_4, 2008/11

 Times Cited Count:43 Percentile:85.02(Physics, Multidisciplinary)

We present inelastic neutron scattering experiments on a single-domain crystal of lightly-doped La$$_{1.96}$$Sr$$_{0.04}$$CuO$$_{4}$$. We find that the magnetic excitation spectrum in this insulating phase with a diagonal incommensurate spin modulation is remarkably similar to that in the superconducting regime, where the spin modulation is bond parallel. In particular, we find that the dispersion slope at low energy is essentially independent of doping and temperature over a significant range. The energy at which the excitations cross the commensurate antiferromagnetic wave vector increases roughly linearly with doping through the underdoped regime.

Journal Articles

Magnetic excitations in overdoped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$

Wakimoto, Shuichi; Yamada, Kazuyoshi*; Tranquada, J. M.*; Frost, C. D.*; Swainson, I.*; Birgeneau, R. J.*

Physica C, 460-462(1), p.166 - 169, 2007/09

 Times Cited Count:1 Percentile:7.1(Physics, Applied)

Spin excitations of overdoped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ ($$0.25 leq x leq 0.30$$) have been studied by neutron scattering utilizing triple-axis and time-of-flight spectrometers. Low-energy excitation spectra ($$omega leq 10$$ $$sim$$meV) for all of the superconducting samples show a maximum around $$omega = 6$$ meV with a maximum value of dynamic spin susceptibility $$chi''(omega)$$ that decreases linearly with ${it T$_{rm c}$}$ as doping increases. The magnetic scattering cross section finally disappears at $$x=0.30$$, coincident with the disappearance of bulk superconductivity. Time-of-flight measurements for $$x=0.25$$ and $$0.30$$ shows markedly suppressed magnetic scattering intensities at intermediate energies (20$$leq$$$$omega$$$$leq$$80$$sim$$meV) in contrast to those of the stripe-ordered La$$_{1.875}$$Ba$$_{0.125}$$CuO$$_{4}$$. These facts imply a cooperative correlation between the dynamic incommensurate state and the superconductivity.

Journal Articles

Disappearance of antiferromagnetic spin excitations in overdoped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$

Wakimoto, Shuichi; Yamada, Kazuyoshi*; Tranquada, J. M.*; Frost, C. D.*; Birgeneau, R. J.*; Zhang, H.*

Physical Review Letters, 98(24), p.247003_1 - 247003_4, 2007/06

 Times Cited Count:80 Percentile:91.81(Physics, Multidisciplinary)

Magnetic excitations for energies up to $$sim100$$ meV are studied for over-doped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ with $$x=0.25$$ and $$0.30$$, using time-of-flight neutron spectroscopy. Comparison of spectra integrated over the width of an antiferromagnetic Brillouin zone demonstrates that the magnetic scattering at intermediate energies,$$20 leq omega leq 100$$ meV, progressively decreases with over-doping. This strongly suggests that the magnetism is not related to Fermi surface nesting, but rather is associated with a decreasing volume fraction of (probably fluctuating) antiferromagnetic bubbles.

Oral presentation

Spin Excitations of overdoped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$

Wakimoto, Shuichi; Birgeneau, R. J.*; Frost, C. D.*; Kagedan, A.*; Kim, H.*; Swainson, I.*; Tranquada, J. M.*; Yamada, Kazuyoshi*; Zhang, H.*

no journal, , 

Spin excitations of LSCO in the overdoped regime has been studied by neutron scattering. Incommensurate excitations around 6 meV which are clearly observed in the $$x=0.25$$ sample decrease with $$T_c$$ as doping increases, and finally, become unobservable at $$x=0.30$$ coincidentally with the disappearance of bulk superconductivity. High-energy measurements performed at the MAPS spectrometer show remarkably weakened magnetic excitations of the overdoped samples also in the high energy region. These observations are apparently consistent with a microscopic phase separation of the overdoped samples into the superconducting and Fermi liquid phases based on muSR results. In contrast, magnetization measurements of overdoped LSCO with and without Zn impurities have revealed that the superconductivity vanishes in the overdoped regime as a result of a competition between the superconductivity and paramagnetism which is induced even in the Zn-free overdoped LSCO.

Oral presentation

Neutron scattering study of magnetic excitations in overdoped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$

Wakimoto, Shuichi; Yamada, Kazuyoshi*; Tranquada, J. M.*; Frost, C. D.*; Birgeneau, R. J.*; Zhang, H.*

no journal, , 

Neutron scattering experiments have been performed on the overdoped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ ($$0.25 leq x leq 0.30$$). Low energy magnetic excitations ($$omega leq 10$$ meV) show incommensurate peaks for the superconducting samples with a maximum at $$sim 6$$ meV in the energy spectrum. As doping increases, the maximum of the dynamic susceptibility decreases linearly with $$T_c$$ and, finally, the low energy excitations become unobservable at $$x=0.30$$ coincidentally with the disappearance of bulk superconductivity. Time-of-flight measurements revealed that magnetic excitations for $$x=0.25$$ are markedly suppressed in the intermediate energy range ($$20 leq omega leq 80$$ meV), which is apparently consistent with a microscopic phase separation into a superconducting region which retains the antiferromagnetic correlations and a Fermi liquid region which has no magnetic correlations.

Oral presentation

Polarized neutron scattering study of spin dynamics in La$$_{2-x}$$(Sr,Ba)$$_{x}$$CuO$$_{4}$$

Wakimoto, Shuichi; Kakurai, Kazuhisa; Matsuda, Masaaki; Takeda, Masayasu; Fujita, Masaki*; Yamada, Kazuyoshi*; Gu, G.*; Tranquada, J. M.*; Birgeneau, R. J.*; Zhang, H.*

no journal, , 

Polarized neutron scattering exaperiments have been performed on La$$_{1.875}$$Ba$$_{0.125}$$CuO$$_{4}$$ and La$$_{1.92}$$Sr$$_{0.08}$$CuO$$_{4}$$ with intent to elucidate a possible effects of stripe structure to the spin dynamics. Low energy ($$omega = 4$$ meV) data demonstratre that in the former sample, which has a well-ordered stripe state with Cu spins lying in the CuO$$_2$$ plane at 10 K, spins fluctuate only in the plane. On the other hand, the latter sample, which has very weak stripe order, shows isotropic spin fluctuation. This implies that low energy magnetic excitations are stringly affected by the stripe order.

Oral presentation

Spin fluctuation and its anisotropy in La$$_{2-x}$$(Sr,Ba)$$_{x}$$CuO$$_{4}$$

Wakimoto, Shuichi; Fujita, Masaki*; Gu, G.*; Kakurai, Kazuhisa; Matsuda, Masaaki; Takeda, Masayasu; Tranquada, J. M.*; Yamada, Kazuyoshi*; Birgeneau, R. J.*; Frost, C. D.*

no journal, , 

To study effects of the stripe structure to the magnetic excitations in the high-$$T_c$$ cuprates, we have performed polarized neutron scattering study on La$$_{1.875}$$Ba$$_{0.125}$$CuO$$_{4}$$ and La$$_{1.92}$$Sr$$_{0.08}$$CuO$$_{4}$$. The former shows robust stripe order whereas the latter has only weak order of stripes. The former shows spin fluctuations which are confined in the CuO$$_2$$ plane, correspondingly to the confinement of the ordered spins in the plane. The latter shows nearly isotropic spin fluctuations. These observations imply that the low-energy spin excitations are strongly affected by the stripe order, which is important to understand the origin of the universal magnetic dispersion in the high-$$T_c$$ cuprates.

Oral presentation

Magnetic excitations in lightly-doped La$$_{2-x}$$Sr$$_x$$CuO$$_4$$

Matsuda, Masaaki; Wakimoto, Shuichi; Fujita, Masaki*; Yamada, Kazuyoshi*; Tranquada, J. M.*

no journal, , 

no abstracts in English

Oral presentation

Magnetic excitations of the diagonal incommensurate phase in lightly-doped La$$_{2-x}$$Sr$$_x$$CuO$$_4$$

Matsuda, Masaaki; Fujita, Masaki*; Wakimoto, Shuichi; Fernandez-Baca, J. A.*; Tranquada, J. M.*; Yamada, Kazuyoshi*

no journal, , 

Neutron scattering experiments were performed in lightly-doped La$$_{1.96}$$Sr$$_{0.04}$$CuO$$_4$$ to study the magnetic excitations in the insulating phase with the diagonal incommensurate spin correlations. It was found that the magnetic excitations at low temperatures are similar to those in the superconducting phase with parallel incommensurate spin correlations. The overall excitation has an hour-glass shape with $$Erm_{cross}sim$$15-25 meV. ($$Erm_{cross}$$ is an energy at which the low-energy excitations cross the antiferromagnetic wave vector.) Furthermore, the effective velocity of the low-energy excitations is approximately independent of doping, so that $$Erm_{cross}$$ scales linearly with doping, following the elastic limit of the magnetic incommensurability. This supports the concept that the magnetic excitations evolve directly from the antiferromagnetic insulator.

Oral presentation

Magnetic dispersion of the diagonal incommensurate phase in lightly-doped La$$_{2-x}$$Sr$$_x$$CuO$$_4$$

Matsuda, Masaaki; Fujita, Masaki*; Wakimoto, Shuichi; Fernandez-Baca, J. A.*; Tranquada, J. M.*; Yamada, Kazuyoshi*

no journal, , 

We performed inelastic neutron scattering experiments on almost single-domain crystals of lightly-doped La$$_{2-x}$$Sr$$_x$$CuO$$_4$$ ($$x$$=0.021 and 0.04). Despite the rotated incommensurability, we find that the spectrum in this insulating phase with a diagonal incommensurate spin modulation is consistent with the hour-glass dispersion observed in superconducting La$$_{2-x}$$Sr$$_x$$CuO$$_4$$ and YBa$$_2$$Cu$$_3$$O$$_{6+x}$$, where the spin modulation is bond parallel. In particular, we find that the energy at which the excitations cross the commensurate antiferromagnetic wave vector increases roughly linearly with doping through the underdoped regime.

Oral presentation

Fe-induced short-range magnetic correlation in Bi$$_{1.75}$$Pb$$_{0.35}$$Sr$$_{1.90}$$Cu$$_{0.91}$$Fe$$_{0.09}$$O$$_{6+y}$$

Wakimoto, Shuichi; Hiraka, Haruhiro*; Kudo, Kazutaka*; Okamoto, Daichi*; Nishizaki, Terukazu*; Kakurai, Kazuhisa; Hong, T.*; Zheludev, A.*; Tranquada, J. M.*; Kobayashi, Norio*; et al.

no journal, , 

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