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Journal Articles

Temperature dependence of spin excitations in the frustrated spin chain system CuGeO$$_3$$

Fujita, Masaki*; Frost, C. D.*; Bennington, S. M.*; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Mizuno, Fumio*; Ikeuchi, Kazuhiko*; Arai, Masatoshi

Journal of the Physical Society of Japan, 82(8), p.084708_1 - 084708_5, 2013/08

 Times Cited Count:1 Percentile:12.72(Physics, Multidisciplinary)

Journal Articles

Ni-substitution effects on the spin dynamics and superconductivity in La$$_{1.85}$$Sr$$_{0.15}$$CuO$$_{4}$$

Matsuura, Masato*; Fujita, Masaki*; Hiraka, Haruhiro*; Kofu, Maiko*; Kimura, Hiroyuki*; Wakimoto, Shuichi; Perring, T. G.*; Frost, C. D.*; Yamada, Kazuyoshi*

Physical Review B, 86(13), p.134529_1 - 134529_8, 2012/10

 Times Cited Count:6 Percentile:31.07(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.

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

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.

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