Y. Endoh - Academia.edu (original) (raw)
Papers by Y. Endoh
Physical Review B, 1999
Neutron-scattering experiments have been performed on lightly-doped La2−xSrxCuO4 single crystals ... more Neutron-scattering experiments have been performed on lightly-doped La2−xSrxCuO4 single crystals in both the insulating (x = 0.03, 0.04, 0.05) and superconducting (x = 0.06) regions. Elastic magnetic peaks are observed at low temperatures in all samples with the maximum peak linewidth occuring at the critical concentration xc = 0.05. New incommensurate peaks are observed only at x = 0.05, the positions of which are rotated by 45 • in reciprocal space about (π, π) from those observed for x ≥ 0.06 in the superconducting phase.
![Research paper thumbnail of Low temperature anomaly of LO phonons in La[sub 1.85]Sr[sub 0.15]CuO[sub 4] and YBa[sub 2]Cu[sub 3]O[sub 7]](https://attachments.academia-assets.com/107250610/thumbnails/1.jpg)
](AIP Conference Proceedings, 1999
Los Alamos National Laboratory, an affirmative actiodequal opportunity employer, is operated by t... more Los Alamos National Laboratory, an affirmative actiodequal opportunity employer, is operated by the University of California for the US. Department of Energy under contract W-7405-ENG-36. By acceptance of this article, the publisher recognizes that the US. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or to allow others to do so, for US. Government purposes. Los Alamos National Laboratory requests that the publisher identify this article as work performed under the auspices of the U.S. Department of Energy. Los Alamos National Laboratory strongly supports academic freedom and a researcher's right to publish; as an institution, however, the Laboratory does not endorse the viewpoint of a publication or guarantee its technical correctness. Form 836 (1 0/96) DISCLAIMER This rcpon was prepared as an account of work sponsored by an agency of the United States Government Neither the United Statu Government nor any agency thmof. nor any of their empioy#r makes any wuranty, exprcy or impiicd, or assumes any legal liability or responsibiiity for the accuracy, cornpictenas, or uscfuincss of any infomation, apparatus, product, or ptoccrs disciosed or repruenu that its use would not infringe privatciy owned rights. Reference herrin to m y spaiic commuci?i product, proccu, or WNiCc by trade name, trademark manufacturer. or otherwise docs not neceulriiy constitute or impiy its tndonnncnt. m mmendation, or favoring by the United States Goveinment or any agency themf. The views and opinions of authors exprcued herein do not n d i y state or reflect thosc of the United Statu Govmment or any agency themf. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.
Journal of Magnetism and Magnetic Materials, 1987
Magnetic susceptibility, electrical resistivity and neutron diffraction measurements of Ce2Sb and... more Magnetic susceptibility, electrical resistivity and neutron diffraction measurements of Ce2Sb and Ce2Bi are reported. A possible valence fluctation for Ce atoms in the metal sheets with a very short inner plane distance is discussed.
Physical Review Letters, 2005
Magnon excitation in a ferromagnetic state of Sm 0:55 Sr 0:45 MnO 3 located on the verge of the m... more Magnon excitation in a ferromagnetic state of Sm 0:55 Sr 0:45 MnO 3 located on the verge of the metalinsulator transition has been studied in terms of the neutron scattering experiment. The anomalous magnon dispersion with the zone-boundary softening is well described by the Heisenberg model with extended exchange coupling constants Js. In particular the fourth neighbor coupling J 4 is as large as 0.6 times the nearest neighbor one J 1. Theoretical analysis based on the local density approximation Hubbard U band calculation reveals that this one-dimensional exchange path is due to the 3z 2 ÿ r 2-type orbital correlation, in sharp contrast to previous proposals.
Cornell University - arXiv, Aug 7, 1998
Scaling relations in the charge and spin excitations of La1−xSrxMnO3 are studied from both theore... more Scaling relations in the charge and spin excitations of La1−xSrxMnO3 are studied from both theoretical and experimental points of view. In the ferromagnetic metal phase, we investigate optical conductivity and neutron inelastic scattering, and compare with a theoretical calculation based on the dynamical mean-field theory of the double-exchange hamiltonian. Spin and charge dynamics of La1−xSrxMnO3 exhibit typical behaviors of half metals. In these manganite compounds with high Curie temperature, various behaviors in spin and charge properties are explained by the doubleexchange hamiltonian alone. Magnetoresistance of these compounds as well as other compounds with lower Curie temperature are also discussed.
Physica C: Superconductivity, 1995
A bulky (7×3×3 mm3) single crystal fo Ca2CuO3 has been successfully prepared by the traveling-sol... more A bulky (7×3×3 mm3) single crystal fo Ca2CuO3 has been successfully prepared by the traveling-solvent-floating-zone (TSFZ) method using CuO excess solvent. An optimum solvent composition for growth of the titled compound was found to be around 9 in CuO/CaO molar ratio R under 0.1 MPa oxygen partial pressure. The obtained R value considerably deviates from the estimated one based on
Neutron scattering and magnetization measurements have been performed on three single crystals of... more Neutron scattering and magnetization measurements have been performed on three single crystals of La{sub 2}CuO{sub 4+{delta}}. For two crystals with {delta}{approx}0.02 and 0.03 phase separation of the intercalated oxygen occurs below 280 K whereas stage ordering occurs below 255 K. A third crystal exhibits no phase separation and a higher stage ordering temperature. All three show evidence for an in- plane ordering around 210 K. We propose a phase diagram which summarizes our observations.
ABSTRACT The spin dynamics of an optimally doped YBa2Cu3O7 (Tc = 93 K) crystal array have been in... more ABSTRACT The spin dynamics of an optimally doped YBa2Cu3O7 (Tc = 93 K) crystal array have been investigated in a wide range of momentum and energy (Q - E) space using the time-of-flight neutron scattering method. Incommensurate spin modulation in Q is a characteristic feature, as it is in the under-doped YBa2Cu3O6.7 with a different incommensurability. A linear relationship between the incommensurability and Tc is proposed. Along with the discovery of the same incommensurability in under-doped La2-ySryCuO4, it may be a generic characteristic of the high-Tc oxide superconductor.
Solid State Communications, 1975
Physica C: Superconductivity, 2000
Physica B: Condensed Matter, 1992
We review the results of neutron scattering studies of the static and dynamic spin fluctuations i... more We review the results of neutron scattering studies of the static and dynamic spin fluctuations in crystals of
Materials Science and Engineering: B, 1999
The gigantic reduction of the electric resistivity under the applied magnetic field, CMR (colossa... more The gigantic reduction of the electric resistivity under the applied magnetic field, CMR (colossal magneto-resistance) effect, is now widely accepted to appear in the vicinity of the insulator to metal transition of the perovskite manganites. Recently, we have discovered the first order transition from ferromagnetic metal to insulator in La 0.88 Sr 0.12 MnO 3 of the CMR manganite. This phase transition induces the tremendous increase of the resistivity under the external magnetic field just near above the phase transition temperature. We report fairly detailed results from the systematic experiments including neutron and synchrotron X-ray scattering studies.
Journal of the Physical Society of Japan, 1999
Journal of Superconductivity, 1997
Systematic neutron scattering measurements have been performed on the Sr-doped La{2-x}SrxCuO4 to ... more Systematic neutron scattering measurements have been performed on the Sr-doped La{2-x}SrxCuO4 to study the doping dependence of spatially modulated dynamical spin correlations or so-called incommensurate spin fluctuations. The modulated spin correlations appear beyond x ≈ 0.05 which is close to the lower boundary of the superconducting phase. First evidence was observed for the linear relation between the degree of spatial
Journal of Physics and Chemistry of Solids, 2008
We report a Cu K-edge resonant inelastic x-ray scattering (RIXS) study of high-Tc cuprates. Momen... more We report a Cu K-edge resonant inelastic x-ray scattering (RIXS) study of high-Tc cuprates. Momentum-resolved charge excitations in the CuO2 plane are examined from parent Mott insulators to carrier-doped superconductors. The Mott gap excitation in undoped insulators is found to commonly show a larger dispersion along the [π, π] direction than the [π, 0] direction. On the other hand, the resonance condition displays material dependence. Upon hole doping, the dispersion of the Mott gap excitation becomes weaker and an intraband excitation appears as a continuum intensity below the gap at the same time. In the case of electron doping, the Mott gap excitation is prominent at the zone center and a dispersive intraband excitation is observed at finite momentum transfer.
Journal of Magnetism and Magnetic Materials, 1998
High-field magnetization measurements up to 40 T and submillimeter wave ESR measurements in frequ... more High-field magnetization measurements up to 40 T and submillimeter wave ESR measurements in frequency range from 95 to 762 GHz have been performed on a stoichiometric single crystal of LaMnO3. At 4.2 K, the induced magnetization curve shows nonlinear increase up to Hc = 21 T for H‖b and linear increase above Hc. This result suggests that the antiferromagnetic easy
Applied Physics A: Materials Science & Processing, 2002
Static antiferromagnetic (AF) spin correlations of overdoped La 2−x Sr x CuO 4 (LSCO) with and wi... more Static antiferromagnetic (AF) spin correlations of overdoped La 2−x Sr x CuO 4 (LSCO) with and without Zn doping have been studied by neutron scattering. In a single crystal of Zn-free LSCO for x = 0.21, no elastic magnetic signals were observed even at 80 mK. However, elastic signals appear below 22 K in 1% Zn-doped LSCO for x = 0.21, indicating that Zn stabilizes the static AF spin correlations even in the overdoped LSCO. The present study confirmed that the AF propagation wave vector is incommensurate with the lattice, characterized as Q AF = (1/2 ∓ η 1/2 ± ε0) with η = 0.005(2) and ε = 0.135(2). The appearance temperature (T m) of the elastic signal degrades under higher-energy resolution, suggesting that the static correlations induced by Zn have a spinglass-like nature.
Physical Review B, 2002
The effects of the application of a magnetic field on the diagonal stripe spin-glass phase is stu... more The effects of the application of a magnetic field on the diagonal stripe spin-glass phase is studied in lightly doped La2−xSrxCuO4 (x=0.014 and 0.024). With increasing magnetic field, the magnetic elastic intensity at the diagonal incommensurate (DIC) positions (1,±ǫ,0) decreases as opposed to the increase seen in superconducting samples. This diminution in intensity with increasing magnetic field originates from a spin reorientation transition, which is driven by the antisymmetric exchange term in the spin Hamiltonian. On the other hand, the transition temperature, the incommensurability, and the peak width of the diagonal incommensurate correlations are not changed with magnetic field. This result suggests that the magnetic correlations are determined primarily by the charge disproportionation and that the geometry of the diagonal incommensurate magnetism is also determined by effects, that is, stripe formation which are not purely magnetic in origin. The Dzyaloshinskii-Moriya antisymmetric exchange is nevertheless important in determining the local spin structure in the DIC stripe phase.
Physical Review Letters, 1995
Neutron inelastic scattering experiments have been performed on homogeneous single crystals of La... more Neutron inelastic scattering experiments have been performed on homogeneous single crystals of La~8sSrp~&Cu04 with T, = 37.3 K (at onset), higher than any previously studied single crystals. The temperature dependence of the low energy incommensurate peak intensity at (7r(1~6), m.) and (7r, rr(1~6)) exhibits a pronounced maximum near T, In co. ntrast to the results reported on lower T, crystals, the intensity below 3.5 meV dramatically decreases as the temperature decreases below T, , vanishing into the background below-15 K. The behavior is consistent with predictions based on a d 2~2 superconducting order parameter.
Physical Review B, 1999
Neutron-scattering experiments have been performed on lightly-doped La2−xSrxCuO4 single crystals ... more Neutron-scattering experiments have been performed on lightly-doped La2−xSrxCuO4 single crystals in both the insulating (x = 0.03, 0.04, 0.05) and superconducting (x = 0.06) regions. Elastic magnetic peaks are observed at low temperatures in all samples with the maximum peak linewidth occuring at the critical concentration xc = 0.05. New incommensurate peaks are observed only at x = 0.05, the positions of which are rotated by 45 • in reciprocal space about (π, π) from those observed for x ≥ 0.06 in the superconducting phase.
AIP Conference Proceedings, 1999
Los Alamos National Laboratory, an affirmative actiodequal opportunity employer, is operated by t... more Los Alamos National Laboratory, an affirmative actiodequal opportunity employer, is operated by the University of California for the US. Department of Energy under contract W-7405-ENG-36. By acceptance of this article, the publisher recognizes that the US. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or to allow others to do so, for US. Government purposes. Los Alamos National Laboratory requests that the publisher identify this article as work performed under the auspices of the U.S. Department of Energy. Los Alamos National Laboratory strongly supports academic freedom and a researcher's right to publish; as an institution, however, the Laboratory does not endorse the viewpoint of a publication or guarantee its technical correctness. Form 836 (1 0/96) DISCLAIMER This rcpon was prepared as an account of work sponsored by an agency of the United States Government Neither the United Statu Government nor any agency thmof. nor any of their empioy#r makes any wuranty, exprcy or impiicd, or assumes any legal liability or responsibiiity for the accuracy, cornpictenas, or uscfuincss of any infomation, apparatus, product, or ptoccrs disciosed or repruenu that its use would not infringe privatciy owned rights. Reference herrin to m y spaiic commuci?i product, proccu, or WNiCc by trade name, trademark manufacturer. or otherwise docs not neceulriiy constitute or impiy its tndonnncnt. m mmendation, or favoring by the United States Goveinment or any agency themf. The views and opinions of authors exprcued herein do not n d i y state or reflect thosc of the United Statu Govmment or any agency themf. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.
Journal of Magnetism and Magnetic Materials, 1987
Magnetic susceptibility, electrical resistivity and neutron diffraction measurements of Ce2Sb and... more Magnetic susceptibility, electrical resistivity and neutron diffraction measurements of Ce2Sb and Ce2Bi are reported. A possible valence fluctation for Ce atoms in the metal sheets with a very short inner plane distance is discussed.
Physical Review Letters, 2005
Magnon excitation in a ferromagnetic state of Sm 0:55 Sr 0:45 MnO 3 located on the verge of the m... more Magnon excitation in a ferromagnetic state of Sm 0:55 Sr 0:45 MnO 3 located on the verge of the metalinsulator transition has been studied in terms of the neutron scattering experiment. The anomalous magnon dispersion with the zone-boundary softening is well described by the Heisenberg model with extended exchange coupling constants Js. In particular the fourth neighbor coupling J 4 is as large as 0.6 times the nearest neighbor one J 1. Theoretical analysis based on the local density approximation Hubbard U band calculation reveals that this one-dimensional exchange path is due to the 3z 2 ÿ r 2-type orbital correlation, in sharp contrast to previous proposals.
Cornell University - arXiv, Aug 7, 1998
Scaling relations in the charge and spin excitations of La1−xSrxMnO3 are studied from both theore... more Scaling relations in the charge and spin excitations of La1−xSrxMnO3 are studied from both theoretical and experimental points of view. In the ferromagnetic metal phase, we investigate optical conductivity and neutron inelastic scattering, and compare with a theoretical calculation based on the dynamical mean-field theory of the double-exchange hamiltonian. Spin and charge dynamics of La1−xSrxMnO3 exhibit typical behaviors of half metals. In these manganite compounds with high Curie temperature, various behaviors in spin and charge properties are explained by the doubleexchange hamiltonian alone. Magnetoresistance of these compounds as well as other compounds with lower Curie temperature are also discussed.
Physica C: Superconductivity, 1995
A bulky (7×3×3 mm3) single crystal fo Ca2CuO3 has been successfully prepared by the traveling-sol... more A bulky (7×3×3 mm3) single crystal fo Ca2CuO3 has been successfully prepared by the traveling-solvent-floating-zone (TSFZ) method using CuO excess solvent. An optimum solvent composition for growth of the titled compound was found to be around 9 in CuO/CaO molar ratio R under 0.1 MPa oxygen partial pressure. The obtained R value considerably deviates from the estimated one based on
Neutron scattering and magnetization measurements have been performed on three single crystals of... more Neutron scattering and magnetization measurements have been performed on three single crystals of La{sub 2}CuO{sub 4+{delta}}. For two crystals with {delta}{approx}0.02 and 0.03 phase separation of the intercalated oxygen occurs below 280 K whereas stage ordering occurs below 255 K. A third crystal exhibits no phase separation and a higher stage ordering temperature. All three show evidence for an in- plane ordering around 210 K. We propose a phase diagram which summarizes our observations.
ABSTRACT The spin dynamics of an optimally doped YBa2Cu3O7 (Tc = 93 K) crystal array have been in... more ABSTRACT The spin dynamics of an optimally doped YBa2Cu3O7 (Tc = 93 K) crystal array have been investigated in a wide range of momentum and energy (Q - E) space using the time-of-flight neutron scattering method. Incommensurate spin modulation in Q is a characteristic feature, as it is in the under-doped YBa2Cu3O6.7 with a different incommensurability. A linear relationship between the incommensurability and Tc is proposed. Along with the discovery of the same incommensurability in under-doped La2-ySryCuO4, it may be a generic characteristic of the high-Tc oxide superconductor.
Solid State Communications, 1975
Physica C: Superconductivity, 2000
Physica B: Condensed Matter, 1992
We review the results of neutron scattering studies of the static and dynamic spin fluctuations i... more We review the results of neutron scattering studies of the static and dynamic spin fluctuations in crystals of
Materials Science and Engineering: B, 1999
The gigantic reduction of the electric resistivity under the applied magnetic field, CMR (colossa... more The gigantic reduction of the electric resistivity under the applied magnetic field, CMR (colossal magneto-resistance) effect, is now widely accepted to appear in the vicinity of the insulator to metal transition of the perovskite manganites. Recently, we have discovered the first order transition from ferromagnetic metal to insulator in La 0.88 Sr 0.12 MnO 3 of the CMR manganite. This phase transition induces the tremendous increase of the resistivity under the external magnetic field just near above the phase transition temperature. We report fairly detailed results from the systematic experiments including neutron and synchrotron X-ray scattering studies.
Journal of the Physical Society of Japan, 1999
Journal of Superconductivity, 1997
Systematic neutron scattering measurements have been performed on the Sr-doped La{2-x}SrxCuO4 to ... more Systematic neutron scattering measurements have been performed on the Sr-doped La{2-x}SrxCuO4 to study the doping dependence of spatially modulated dynamical spin correlations or so-called incommensurate spin fluctuations. The modulated spin correlations appear beyond x ≈ 0.05 which is close to the lower boundary of the superconducting phase. First evidence was observed for the linear relation between the degree of spatial
Journal of Physics and Chemistry of Solids, 2008
We report a Cu K-edge resonant inelastic x-ray scattering (RIXS) study of high-Tc cuprates. Momen... more We report a Cu K-edge resonant inelastic x-ray scattering (RIXS) study of high-Tc cuprates. Momentum-resolved charge excitations in the CuO2 plane are examined from parent Mott insulators to carrier-doped superconductors. The Mott gap excitation in undoped insulators is found to commonly show a larger dispersion along the [π, π] direction than the [π, 0] direction. On the other hand, the resonance condition displays material dependence. Upon hole doping, the dispersion of the Mott gap excitation becomes weaker and an intraband excitation appears as a continuum intensity below the gap at the same time. In the case of electron doping, the Mott gap excitation is prominent at the zone center and a dispersive intraband excitation is observed at finite momentum transfer.
Journal of Magnetism and Magnetic Materials, 1998
High-field magnetization measurements up to 40 T and submillimeter wave ESR measurements in frequ... more High-field magnetization measurements up to 40 T and submillimeter wave ESR measurements in frequency range from 95 to 762 GHz have been performed on a stoichiometric single crystal of LaMnO3. At 4.2 K, the induced magnetization curve shows nonlinear increase up to Hc = 21 T for H‖b and linear increase above Hc. This result suggests that the antiferromagnetic easy
Applied Physics A: Materials Science & Processing, 2002
Static antiferromagnetic (AF) spin correlations of overdoped La 2−x Sr x CuO 4 (LSCO) with and wi... more Static antiferromagnetic (AF) spin correlations of overdoped La 2−x Sr x CuO 4 (LSCO) with and without Zn doping have been studied by neutron scattering. In a single crystal of Zn-free LSCO for x = 0.21, no elastic magnetic signals were observed even at 80 mK. However, elastic signals appear below 22 K in 1% Zn-doped LSCO for x = 0.21, indicating that Zn stabilizes the static AF spin correlations even in the overdoped LSCO. The present study confirmed that the AF propagation wave vector is incommensurate with the lattice, characterized as Q AF = (1/2 ∓ η 1/2 ± ε0) with η = 0.005(2) and ε = 0.135(2). The appearance temperature (T m) of the elastic signal degrades under higher-energy resolution, suggesting that the static correlations induced by Zn have a spinglass-like nature.
Physical Review B, 2002
The effects of the application of a magnetic field on the diagonal stripe spin-glass phase is stu... more The effects of the application of a magnetic field on the diagonal stripe spin-glass phase is studied in lightly doped La2−xSrxCuO4 (x=0.014 and 0.024). With increasing magnetic field, the magnetic elastic intensity at the diagonal incommensurate (DIC) positions (1,±ǫ,0) decreases as opposed to the increase seen in superconducting samples. This diminution in intensity with increasing magnetic field originates from a spin reorientation transition, which is driven by the antisymmetric exchange term in the spin Hamiltonian. On the other hand, the transition temperature, the incommensurability, and the peak width of the diagonal incommensurate correlations are not changed with magnetic field. This result suggests that the magnetic correlations are determined primarily by the charge disproportionation and that the geometry of the diagonal incommensurate magnetism is also determined by effects, that is, stripe formation which are not purely magnetic in origin. The Dzyaloshinskii-Moriya antisymmetric exchange is nevertheless important in determining the local spin structure in the DIC stripe phase.
Physical Review Letters, 1995
Neutron inelastic scattering experiments have been performed on homogeneous single crystals of La... more Neutron inelastic scattering experiments have been performed on homogeneous single crystals of La~8sSrp~&Cu04 with T, = 37.3 K (at onset), higher than any previously studied single crystals. The temperature dependence of the low energy incommensurate peak intensity at (7r(1~6), m.) and (7r, rr(1~6)) exhibits a pronounced maximum near T, In co. ntrast to the results reported on lower T, crystals, the intensity below 3.5 meV dramatically decreases as the temperature decreases below T, , vanishing into the background below-15 K. The behavior is consistent with predictions based on a d 2~2 superconducting order parameter.