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Journal Articles

Magnetic nature of the 500 meV peak in La$$_{2-x}$$Sr$$_x$$CuO$$_4$$ observed with resonant inelastic X-ray scattering at the Cu $$K$$-edge

Ellis, D. S.*; Kim, J.*; Hill, J. P.*; Wakimoto, Shuichi; Birgeneau, R. J.*; Shvyd'ko, Y.*; Casa, D.*; Gog, T.*; Ishii, Kenji; Ikeuchi, Kazuhiko*; et al.

Physical Review B, 81(8), p.085124_1 - 085124_12, 2010/02

 Times Cited Count:36 Percentile:80.58(Materials Science, Multidisciplinary)

Journal Articles

Muon spin rotation measurements of heterogeneous field response in overdoped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$

MacDougall, G. J.*; Savici, A. T.*; Aczel, A. A.*; Birgeneau, R. J.*; Kim, H.*; Kim, S.-J.*; Ito, Toshimitsu*; Rodriguez, J. A.*; Russo, P. L.*; Uemura, Yasutomo*; et al.

Physical Review B, 81(1), p.014508_1 - 014508_7, 2010/01

 Times Cited Count:9 Percentile:43.25(Materials Science, Multidisciplinary)

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.

Journal Articles

Incommensurate lattice distortion in the high temperature tetragonal phase of La$$_{2-x}$$(Sr,Ba)$$_{x}$$CuO$$_{4}$$

Wakimoto, Shuichi; Kimura, Hiroyuki*; Fujita, Masaki*; Yamada, Kazuyoshi*; Noda, Yukio*; Shirane, Gen*; Gu, G.*; Kim, H.*; Birgeneau, R. J.*

Journal of the Physical Society of Japan, 75(7), p.074714_1 - 074714_6, 2006/07

 Times Cited Count:20 Percentile:70.95(Physics, Multidisciplinary)

We report incommensurate diffuse (ICD) scattering appearing in the high-temperature-tetragonal (HTT) phase of La$$_{2-x}$$(Sr,Ba)$$_{x}$$CuO$$_{4}$$ with $$0.07leq xleq 0.20$$ observed by the neutron diffraction technique. For all compositions, a sharp superlattice peak of the low-temperature-orthorhombic (LTO) structure is replaced by a pair of ICD peaks with the modulation vector parallel to the CuO$$_6$$ octahedral tilting direction, that is, the diagonal Cu-Cu direction of the CuO$$_2$$ plane, above the LTO-HTT transition temperature $$T_s$$. The temperature dependences of the incommensurability $$delta$$ for all samples scale approximately as $$T/T_s$$, while those of the integrated intensity of the ICD peaks scale as $$(T-T_s)^{-1}$$. These observations together with absence of ICD peaks in the non-superconducting $$x=0.05$$ sample evince a universal incommensurate lattice instability of hole-doped 214 cuprates in the superconducting regime.

Journal Articles

Muon spin rotation study of field-induced magnetism in heavily overdoped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$

MacDougall, G. J.*; Birgeneau, R. J.*; Kim, H.*; Kim, S.-J.*; Rodriguez, J.*; Russo, P. L.*; Savici, A. T.*; Uemura, Yasutomo*; Wakimoto, Shuichi; Wiebe, C. R.*; et al.

Physica B; Condensed Matter, 374-375, p.211 - 214, 2006/03

 Times Cited Count:4 Percentile:23.8(Physics, Condensed Matter)

In the huge volume of research on the cuprates, there is very little that investigates the properties of the highly overdoped area of the phase diagram, where superconductivity disappears with increased carrier concentration. In the spirit of further exploring this region, we have performed the first known $$mu$$SR measurements of heavily overdoped single-crystalline La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$. We discovered an anomalous field-induced broadening of the internal magnetic field distribution. The broadening is linear in applied field and has a Curie-Weiss temperature dependence. Furthermore, the effect increases with doping above $$x=0.12$$ and is maximal at our highest doping ($$x=0.3$$). Possible relaxation mechanisms are discussed.

Journal Articles

Neutron scattering and magnetization studies of Ba$$_{2}$$Cu$$_{2.95}$$Co$$_{0.05}$$O$$_{4}$$Cl$$_{2}$$; A Decorated two-dimensional antiferromagnet

Ramazanoglue, M. K.*; Clegg, P. S.*; Wakimoto, Shuichi; Birgeneau, R. J.*; Noro, Sumiko*

Physical Review B, 73(5), p.054418_1 - 054418_6, 2006/02

 Times Cited Count:1 Percentile:7.01(Materials Science, Multidisciplinary)

Ba$$_{2}$$Cu$$_{3}$$O$$_{4}$$Cl$$_{2}$$ has two penetrating square Cu sublattices, one with square root 2 times the in-plane spacing of the other. Isotropic magnetic interactions between the two sublattices are completely frustrated. Quantum fluctuations resolve the intrinsic degeneracy in the ordering direction of the more weakly coupled sublattices in favor of collinear ordering. We present neutron scattering and magnetization studies of the magnetic structure when the Cu ions are substituted with Co. The Co pairs create new magnetic interactions between the two sublattices. The ordering behavior of both Cu sublattices is retained largely unmodified. Between the phase transitions of the two sublattices spin-glass behavior is observed. Magnetization results show a strong enhancement to the ferromagnetic aspect of the magnetic structure. The combination of glassy behavior and large moments strongly suggest that the Co moments induce the formation of local canted states.

Journal Articles

Resonant inelastic X-ray scattering study of overdoped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$

Wakimoto, Shuichi; Kim, Y.-J.*; Kim, H.*; Zhang, H.*; Gog, T.*; Birgeneau, R. J.*

Physical Review B, 72(22), p.224508_1 - 224508_7, 2005/12

 Times Cited Count:12 Percentile:49.29(Materials Science, Multidisciplinary)

Resonant inelastic X-ray scattering (RIXS) at the copper Kabsorption edge has been performed for heavily overdoped samplesof La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ with $$x= 0.25$$ and $$0.30$$. We have observed the chargetransfer and molecular orbital excitations which exhibit resonances at incident energies of $$E_i= 8.992$$ and $$8.998$$ keV,respectively. From a comparison with previous results on undoped andoptimally-doped samples, we determine that the charge transfer excitation energy increases monotonically as doping increases. In addition, the $$E_i$$-dependences of the RIXS spectral weight and absorption spectrum exhibit no clear peak at $$E_i = 8.998$$ keV in contrast to results in the underdoped samples. The low-energy ($$leq 3$$ eV) continuum excitation intensity has been studied utilizing the high energy resolution of 0.13 eV (FWHM). A comparison of the RIXS profiles at $$(pi 0)$$ and $$(pi pi)$$ indicates that the continuum intensity exists even at $$(pi pi)$$ in the overdoped samples, while it has been reported only at $$(0 0)$$ and $$(pi 0)$$ for the $$x=0.17$$ sample. Furthermore, we also found an additional excitation on top of the continuum intensity at the $$(pi pi)$$ and $$(pi 0)$$ positions.

Journal Articles

Magnetic properties of the overdoped superconductor La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ with and without Zn impurities

Wakimoto, Shuichi; Birgeneau, R. J.*; Kagedan, A.*; Kim, H.-K.*; Swainson, I.*; Yamada, Kazuyoshi*; Zhang, H.*

Physical Review B, 72(6), p.064521_1 - 064521_9, 2005/08

 Times Cited Count:27 Percentile:71.83(Materials Science, Multidisciplinary)

The magnetic properties of the Zn-substituted overdoped high-$$T_c$$ superconductor La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ (LSCO) have been studied by magnetization measurements and neutron scattering. Magnetization measurements reveal that for Zn-free samples with $$x geq 0.22$$ a Curie term is induced implying the existence of local paramagnetic moments. A comparison of the Curie behaviour between Zn-doped and Zn-free samples signifies a general competitive relationship between the superconductivity and the induced paramagnetic moment. Neutron scattering measurements show that Zn-substitution in overdoped LSCO anomalously enhances the inelastic magnetic scattering spectra around the $$(pi, pi)$$ position, peaking at $$omega sim 7$$meV. These facts are discussed on the basis of a "swiss-cheese" model of Zn-substituted systems as well as a microscopic phase separation scenario in the overdoped region indicated by muon-spin-relaxation measurements.

Journal Articles

Field-induced transition between magnetically disordered and ordered phases in underdoped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$

Khaykovich, B.*; Wakimoto, Shuichi; Birgeneau, R. J.*; Kastner, M. A.*; Lee, Y. S.*; Smeibidle, P.*; Vorderwisch, P.*; Yamada, Kazuyoshi*

Physical Review B, 71(22), p.220508_1 - 220508_4, 2005/06

 Times Cited Count:71 Percentile:90.08(Materials Science, Multidisciplinary)

Magnetic field-induced transition between magnetically disordered and ordered phases in slightly under-doped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ with $$x=0.144$$ has been observed. Static incommensurate spin-density-wave order is induced above a critical field of about 3 T, as measured by elastic neutron scattering. These results are consistent with recently developed quantum phase transition scenario.

Journal Articles

Magnetic field effects and magnetic anisotropy in lightly doped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$

Matsuda, Masaaki; Fujita, Masaki*; Yamada, Kazuyoshi*; Birgeneau, R. J.*; Endo, Yasuo*; Shirane, Gen*

Physical Review B, 66(17), p.174508_1 - 174508_6, 2002/11

 Times Cited Count:11 Percentile:51.99(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Electronic phase separation in lightly doped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$

Matsuda, Masaaki; Fujita, Masaki*; Yamada, Kazuyoshi*; Birgeneau, R. J.*; Endo, Yasuo*; Shirane, Gen*

Physical Review B, 65(13), p.134515_1 - 134515_6, 2002/04

 Times Cited Count:137 Percentile:96.78(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Neutron scattering studies on lightly-doped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$

Matsuda, Masaaki; Birgeneau, R. J.*; Endo, Yasuo*; Fujita, Masaki*; Hiraka, Haruhiro*; Kastner, M. A.*; Shirane, Gen*; Wakimoto, Shuichi*; Yamada, Kazuyoshi*

Journal of the Physical Society of Japan, Vol.70, Supplement A, p.46 - 48, 2001/05

no abstracts in English

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

Incommensurate lattice distortion in the high temperature tetragonal phase of La$$_{2-x}$$(Sr,Ba)$$_{x}$$CuO$$_{4}$$

Wakimoto, Shuichi; Kimura, Hiroyuki*; Fujita, Masaki*; Yamada, Kazuyoshi*; Noda, Yukio*; Shirane, Gen*; Gu, G.*; Kim, H.*; Birgeneau, R. J.*

no journal, , 

We report incommensurate diffuse (ICD) scattering appearing in the high-temperature-tetragonal (HTT) phase of La$$_{2-x}$$(Sr,Ba)$$_{x}$$CuO$$_{4}$$ with 0.07 $$leq$$ $$times$$ $$leq$$ 0.20 observed by the neutron diffraction technique. For all compositions, a sharp superlattice peak of the low-temperature-orthorhombic (LTO) structure is replaced by a pair of ICD peaks with a modulation vector parallel to the CuO$$_6$$ octahedral tilting direction, that is, the diagonal Cu-Cu direction of the CuO$$_2$$ plane, above the LTO-HTT transition temperature $$T_s$$. The temperature dependences of incommensurability $$delta$$ for all samples scale approximately to $$T/T_s$$, while those of integrated intensity of the ICD peaks scale to $$T-T_s$$. Those observations together with absence of ICD peaks in the non-superconducting $$x=0.05$$ sample evince a universal incommensurate lattice instability of hole-doped 214 cuprates in the superconducting regime.

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.

18 (Records 1-18 displayed on this page)
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