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Neutron Scattering Studies Of The Electron Doped High Temperature Superconductor Neodymium Cerium Copper Oxide
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Book Synopsis Neutron Scattering Studies of the Electron-doped High-temperature Superconductor Neodymium Cerium Copper Oxide by : Eugene M. Motoyama
Download or read book Neutron Scattering Studies of the Electron-doped High-temperature Superconductor Neodymium Cerium Copper Oxide written by Eugene M. Motoyama and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: While the mechanism for the high transition temperatures (Tc) in the cuprate superconductors remains unsolved, antiferromagnetic fluctuations on the copper-oxygen sheets are thought to play an important role. Long-range antiferromagnetic order is present in the undoped insulating parent compounds, whereas superconductivity is observed when these materials are doped with a sufficient number of holes or electrons. Because these two phases are well separated on the hole-doped side of the phase diagram, the interplay between antiferromagnetism and superconductivity is perhaps better studied in the electron-doped compounds, where the two phases appear to overlap. In this Thesis work, single crystals of electron-doped Nd{2-x}Ce{x}CuO4 (NCCO) were grown over a wide range of cerium concentration, and the following two neutron scattering studies were performed on these crystals. In the first study, an energy-integrating neutron scattering method is used to measure the two-dimensional instantaneous magnetic correlation length as a function of temperature and doping. For x 0.12, the correlation length diverges at the same temperature at which magnetic Bragg peaks appear, as expected. For x 0.12, on the other hand, the correlation length remains finite down to the lowest measured temperatures. Since bulk superconductivity is only found above about x=0.13, this shows that there is no genuine coexistence between superconductivity and long-range antiferromagnetic order, which was previously thought to extend to x = 0.17. The second study is the first inelastic neutron scattering investigation of an electron-doped cuprate superconductor in an applied magnetic field. This experiment measures how the weakening of superconductivity due to a magnetic field affects the antiferromagnetic response. An advantage of the electron-doped cuprates is that the critical field Hc2 required to completely suppress superconductivity is relatively low (~10 T). In zero field, the antiferromagnetic excitation spectrum of NCCO (x=0.166) is gapped below 2.5 meV. The gap energy is found to decrease linearly with applied field and to extrapolate to zero near Hc2. The observed behavior indicates that the non-superconducting ground state is similar to the (zero-field) paramagnetic state at temperatures above Tc, and thus that superconductivity and antiferromagnetism are not competing orders in this part of the phase diagram.
Book Synopsis Magnetic, Phonon, and Structural Scattering Studies of the Electron-doped High-temperature Superconductor Neodymium Cerium Copper Oxide by : Patrick Kingsley Mang
Download or read book Magnetic, Phonon, and Structural Scattering Studies of the Electron-doped High-temperature Superconductor Neodymium Cerium Copper Oxide written by Patrick Kingsley Mang and published by . This book was released on 2004 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Neutron Scattering Studies of Cuprates and Iron Pnictides by : Mengshu Liu (Physicist)
Download or read book Neutron Scattering Studies of Cuprates and Iron Pnictides written by Mengshu Liu (Physicist) and published by . This book was released on 2014 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presented within are neutron scattering studies of several different high temperature superconducting materials: BaFe1.9Ni0.1As2 [Barium Iron Nickel Arsenic], BaFe1.85Ni0.15As2 [Barium Iron Nickel Arsenic], Ba0.67K0.33Fe2As2 [Barium Potassium Iron Arsenic], and Pr0.88LaCe0.12CuO4-y [Praseodymium Lanthanum Cerium Copper Oxide]. The main focus is on the magnetic excitations within the systems. For BaFe1.9Ni0.1As2 [Barium Iron Nickel Arsenic], we measured the intensity of its magnetic excitations and compared the results with excitations in antiferromagnetic non-superconducting BaFe2As2 [Barium Iron Arsenic]. We find electron-doping only affects spin excitations below 100 meV while the total size of the magnetic moment and the energy distribution do not change much. It shows that the magnetic moments in both materials are similar to insulating copper oxides, an indicator of the importance of strong electron correlations in high temperature superconductivity. For both BaFe1.85Ni0.15As2 [Barium Iron Nickel Arsenic] and Ba0.67K0.33Fe2As2 [Barium Potassium Iron Arsenic], we use polarized inelastic neutron scattering to study their low-energy spin excitations and their spatial anisotropy. Our neutron polarization analysis reveals that magnetic excitations are isotropic for the in-plane and out-of-plane components in both the normal and superconducting states for BaFe1.85Ni0.15As2 [Barium Iron Nickel Arsenic], while in Ba0.67K0.33Fe2As2 [Barium Potassium Iron Arsenic] large difference in spin gaps were found. A comparison of these results with those of undoped BaFe2As2 [Barium Iron Arsenic] and optimally electron-doped BaFe1.9Ni0.1As2 [Barium Iron Nickel Arsenic] suggests that the spin anisotropy observed Ba0.67K0.33Fe2As2 [Barium Potassium Iron Arsenic] are likely due to their proximity to their parent compound, where spin anisotropy exists below TN [Neel Temperature], while the neutron spin resonance is isotropic in the overdoped regime, consistent with a singlet to triplet excitation. For as-grown and optimal superconducting Pr0.88LaCe0.12CuO4-y [Praseodymium Lanthanum Cerium Copper Oxide] (PLCCO), we measured their magnetic excitations over a wide energy range, and compared their corresponding results. The spectra is considerably larger throughout the whole zone in as-grown PLCCO, than in the optimal superconducting PLCCO, which is very different from the BaFe2As2 [Barium Iron Arsenic] system.
Book Synopsis Study Magnetic Excitations in Doped Transition Metal Oxides Using Inelastic Neutron Scattering by :
Download or read book Study Magnetic Excitations in Doped Transition Metal Oxides Using Inelastic Neutron Scattering written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the interplay between magnetism and superconductivity continues to be a "hot" topic in modern condensed matter physics. The discovery of high-temperature superconductivity in iron-based materials in 2008 provided an unique opportunity to compare and contrast these materials with traditional high-Tc copper oxide superconductors. Neutron scattering plays an important role in determining the dynamical spin properties in these materials. This proposal is a continuation of previous DOE supported proposal. This report summarizes the final progress we have made over from May 2005 till Aug. 2013. Overall, we continue to carry out extensive neutron scattering experiments on Fe-based materials, focusing on understanding their magnetic properties. In addition, we have established a materials laboratory at UT that has allowed us to grow these superconductors. Because neutron scattering typically demands a large amount of samples, by growing these materials in our own laboratory, we can now pursuit neutron scattering experiments over the entire electronic phase diagram, focusing on regions of interests. The material synthesis laboratory at UT was established entirely with the support of DOE funding. This not only allowed us to carry out neutron scattering experiments, but also permit us to provide samples to other US/International collaborators for studying these materials.
Book Synopsis Neutron Scattering Studies on Magnetism and Phonon in the Electron-doped Nd2[subscript X]Ce[subscript X]CuO4 and Pr1[subscript X]LaCe[subscript X]CuO4 by :
Download or read book Neutron Scattering Studies on Magnetism and Phonon in the Electron-doped Nd2[subscript X]Ce[subscript X]CuO4 and Pr1[subscript X]LaCe[subscript X]CuO4 written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present comprehensive neutron scattering studies on the electron-doped superconductors Nd2[subscript x]Ce[subscript x]CuO4 and Pr1[subscript x]LaCe[subscript x]CuO4 to understand how magnetic properties and phonon are related to superconductivity. For superconducting Nd1[subscript point]5Ce0[subscript point]15CuO4, a[italicized c]-axis magnetic field enhances the commensurate antiferromagnetic order, while an [italicized ab]-plane magnetic field induces spin-flop transition from a noncollinear to a collinear magnetic structure. The [italicized c]-axis field-induced effect is absent in both parent Nd2CuO4 and the as-grown nonsuperconducting Nd1[subscript point]5Ce0[subscript point]15CuO4 samples. These results, combined with those on the hole-doped La2−[subscript x]Sr[subscript x]CuO4 suggest that the antiferromagnetism competes with supercondictivity. In the Pr1−[subscript x]LaCe[subscript x]CuO4 system, we find that quasi-2 dimensional commensurate antiferromagnetism coexists with superconductivity and 3 dimensional antiferromagnetism. To determine whether the antiferromagnetic order is the competing order in the high temperature superconductors, regardless of hole-doping or electron-doping, we performed field-induced experiments on the electron-doped superconductor Pr0[subscript point]88LaCe0[subscript point]12CuO4[subscript plus or minus delta] by applying magnetic fields along the [italicized c]-direction and in the [italicized ab]-plane direction. The anisotropy of the field-induced moment demonstrates the competing nature of these two order parameters. We find that the spin-flop transition induced by an [italicized ab]-plane magnetic field in the lightly electron-doped Pr1[subscript point]29La0[subscript point]--Ce0[subscript point]01CuO4 affects significantly both in-plane and out-of-plane resistivity. No magnetoresistance anomaly is observed when a [italicized c]-axis magnetic field is applied, consistent with the absence of a spin-flop transition for such field direction. This anisotropic magnetoresistance effect suggests that there is spin-charge coupling in the electron-doped superconductors as well as in the hole-doped ones. Inelastic neutron scattering has been performed to study the generalized phonon density of states (GDOS) of electron-doped Nd2−[subscript x]Ce[subscript x]CuO4 with various levels of doping. Upon doping, the softening of phonon around 70 me V has been observed. However, most of the softening occurs within a few percent of Ce doping, and it is not related to the doping induced nonsuperconducting-superconducting transition. Therefore, the electron-lattice coupling in the electron-doped Nd2−[subscript x]Ce[subscript x]CuO4 is different from that in the hole-doped materials.
Book Synopsis (Neutron Scattering Studies of the High-temperature Superconducting Materials). by :
Download or read book (Neutron Scattering Studies of the High-temperature Superconducting Materials). written by and published by . This book was released on 1991 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: The traveler was given beam time at the ILL to continue neutron scattering work on high-temperature superconductivity. The unique facilities at the ILL for both high-energy and low-energy neutron instrumentation made the experiments possible. The measurements consisted of two basic types. The first of these is the study of the nature of spin fluctuations in high-{Tc} materials. This work is fundamental to the mechanism that is responsible for the high-transition temperatures. The second consisted of experiments on the flux lattice in high-temperature superconductors. The flux lattice has interesting physics in its own right and is important in understanding the current-carrying capability of superconductors.
Book Synopsis Neutron Scattering Study of High Tc Superconductors by : Jun Zhao
Download or read book Neutron Scattering Study of High Tc Superconductors written by Jun Zhao and published by . This book was released on 2010 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: We carried out systematic neutron scattering experiments to investigate the magnetic properties and their relationship to the high-Tc superconductivity, when the materials are tuned from their antiferromagnetic (AF) parent compounds to the superconducting regime. We observed resonance mode in the electron doped cuprate Nd[subscript 1.85]Ce[subscript 0.15]CuO[subscript 4], demonstrating that the resonance is a general phenomenon in cuprate superconductors regardless of hole- or electron-doping. In Pr[subscript 0.88]LaCe[subscript 0.12]CuO[subscript 4], the local susceptibility displays two distinct energy scales that are broadly consistent with the bosonic modes revealed by scanning tunneling microscopy experiments. These results indicate the presence of very strong electron spin excitations couplings in electron doped cuprates. Shortly after the discovery of high-Tc superconductivity in the Fe pnictides, we discovered that the magnetic phase diagram of CeFeAsO[subscript 1-x]F[subscript x] is remarkably similar to that of the cuprates. Besides CeFeAsO, similar magnetic and lattice structures are also observed in PrFeAsO and SrFe[subscript 2]As[subscript 2] systems. Neutron scattering measurements show that in SrFe[subscript 2]As[subscript 2], the spectrum of magnetic excitations consists of a Bragg peak at the elastic position, a spin gap, and sharp spin-wave excitations at higher energies. Based on the observed dispersion relation, we estimated the effective magnetic exchange coupling using a Heisenberg model. In order to study the nature of the exchange interactions in the parent compound of Fe pnictides, we studied the high energy spin-wave excitations in CaFe2As2. Although the spin waves in the entire Brillouin zone can be described by an effective three-dimensional anisotropic Heisenberg Hamiltonian, the magnetism in this system is neither purely local nor purely itinerant; rather it is a complicated mix of the two. When the Fe pnictide is tuned into superconducting regime with doping, the low energy spin fluctuation is dominated by a resonance mode. In the optimally electron doped BaFe[subscript 1.9]Ni[subscript 0.1]As[subscript 2], application of a magnetic field that suppresses the superconductivity and superconducting gap energy also reduces the intensity and energy of the resonance. These results suggest that the energy of the resonance is proportional to the electron pairing energy, and thus indicate that spin fluctuations are intimately related to the mechanism of high Tc superconductivity.
Book Synopsis Dissertation Abstracts International by :
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2004 with total page 788 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Neutron Scattering Studies of the High Temperature Superconductor Bi2Sr2CaCu2O8+x by : Philip Andrew Miles
Download or read book Neutron Scattering Studies of the High Temperature Superconductor Bi2Sr2CaCu2O8+x written by Philip Andrew Miles and published by . This book was released on 1999 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Neutron Scattering Studies of Spin-phonon Hybridization and Superconducting Spin Gaps in the High Temperature Superconductor La2-x(Sr;Ba)xCuO4 by :
Download or read book Neutron Scattering Studies of Spin-phonon Hybridization and Superconducting Spin Gaps in the High Temperature Superconductor La2-x(Sr;Ba)xCuO4 written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present time-of-flight neutron-scattering measurements on single crystals of La2-xBaxCuO4 (LBCO) with 0 ≤ x ≤ 0.095 and La2-xSrxCuO4 (LSCO) with x = 0.08 and 0.11. This range of dopings spans much of the phase diagram relevant to high temperature cuprate superconductivity, ranging from insulating, three dimensional commensurate long range antiferromagnetic order for x ≤ 0.02 to two dimensional (2D) incommensurate antiferromagnetism co-existing with superconductivity for x ≥ 0.05. Previous work on lightly doped LBCO with x = 0.035 showed a clear resonant enhancement of the inelastic scattering coincident with the low energy crossings of the highly dispersive spin excitations and quasi-2D optic phonons. The present work extends these measurements across the phase diagram and shows this enhancement to be a common feature to this family of layered quantum magnets. Furthermore we show that the low temperature, low energy magnetic spectral weight is substantially larger for samples with non-superconducting ground states relative to any of the samples with superconducting ground states. Lastly spin gaps, suppression of low energy magnetic spectral weight, are observed in both superconducting LBCO and LSCO samples, consistent with previous observations for superconducting LSCO.
Book Synopsis Neutron Scattering, [mu]SR and Magnetic Studies of Compounds Related to High Temperature Superconductors by : Jason Stewart Gardner
Download or read book Neutron Scattering, [mu]SR and Magnetic Studies of Compounds Related to High Temperature Superconductors written by Jason Stewart Gardner and published by . This book was released on 1996 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Neutron Scattering Studies of Magnetic Correlations in the Layered Cuprates by :
Download or read book Neutron Scattering Studies of Magnetic Correlations in the Layered Cuprates written by and published by . This book was released on 1989 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: All of the copper oxide superconductors contain CuO2 layers which, when insulating, exhibit strong, two-dimensional (2D) antiferromagnetic correlations due to the unusually large superexchange interaction between nearest-neighbor Cu{sup 2+} atoms. Magnetic correlations survive, although with a reduced correlation length, even when the layers are doped with holes. A short review of neutron scattering studies of magnetic correlations and excitations in the layered cuprates is presented. 19 refs., 6 figs.
Book Synopsis Neutron Scattering Study of Magnetic Excitations in Two High-temperature Superconductors by : Guichuan Yu
Download or read book Neutron Scattering Study of Magnetic Excitations in Two High-temperature Superconductors written by Guichuan Yu and published by . This book was released on 2008 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Neutron Scattering MuSR and Magnetic Studies of Compounds Related to High Temperature Superconductors by : Jason Stewart Gardner
Download or read book Neutron Scattering MuSR and Magnetic Studies of Compounds Related to High Temperature Superconductors written by Jason Stewart Gardner and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Neutron Scattering Study of the Interplay Between Structure and Magnetism in Ba(Fe1−xCox)2As2 by :
Download or read book A Neutron Scattering Study of the Interplay Between Structure and Magnetism in Ba(Fe1−xCox)2As2 written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Single crystal neutron diffraction is used to investigate the magnetic and structural phase diagram of the electron doped superconductor Ba(Fe{sub 1-x}Co(subscript x))2As2. Heat capacity and resistivity measurements have demonstrated that Co doping this system splits the combined antiferromagnetic and structural transition present in BaFe2As2 into two distinct transitions. For x=0.025, we find that the upper transition is between the high-temperature tetragonal and low-temperature orthorhombic structures with (T{sub TO} = 99 ± 0.5 K) and the antiferromagnetic transition occurs at T{sub AF} = 93 ± 0.5 K. We find that doping rapidly suppresses the antiferromagnetism, with antiferromagnetic order disappearing at x (almost equal to) 0.055. However, there is a region of co-existence of antiferromagnetism and superconductivity. The effect of the antiferromagnetic transition can be seen in the temperature dependence of the structural Bragg peaks from both neutron scattering and x-ray diffraction. We infer from this that there is strong coupling between the antiferromagnetism and the crystal lattice.
Book Synopsis Neutron and Synchrotron X-Ray Scattering Studies of Superconductors by :
Download or read book Neutron and Synchrotron X-Ray Scattering Studies of Superconductors written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Superconductors hold the promise for a more stable and efficient electrical grid, but new isotropic, high-temperature superconductors are needed in order to reduce cable manufacturing costs. The effort to understand high-temperature superconductivity, especially in the layered cuprates, provides guidance to the search for new superconductors. Neutron scattering has long provided an important probe of the collective excitations that are involved in the pairing mechanism. For the cuprates, neutron and x-ray diffraction techniques also provide information on competing types of order, such as charge and spin stripes, that appear to be closely connected to the superconductivity. Recently, inelastic x-ray scattering has become competitive for studying phonons and may soon provide valuable information on electronic excitations. Examples of how these techniques contribute to our understanding of superconductivity are presented.
Author :Chris Stock Publisher :Library and Archives Canada = Bibliothèque et Archives Canada ISBN 13 :9780494028919 Total Pages :366 pages Book Rating :4.0/5 (289 download)
Book Synopsis Neutron Scattering Studies of Superconducting YBa↓2Cu↓2O↓6↓+↓x and Relaxor Ferroelectrics Pb(Mg↓1↓ by : Chris Stock
Download or read book Neutron Scattering Studies of Superconducting YBa↓2Cu↓2O↓6↓+↓x and Relaxor Ferroelectrics Pb(Mg↓1↓ written by Chris Stock and published by Library and Archives Canada = Bibliothèque et Archives Canada. This book was released on 2005 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: The lattice dynamics and structural properties were measured in the ferroelectrics Pb(Mg1/3Nb2/3)O3 and Pb(Zn1/3Nb 2/3)O3. Relaxor ferroelectrics have attracted much attention recently due to their exceptional piezoelectric properties. Despite the previous belief that these two materials are very different, the lattice dynamics are found to be nearly identical. The main difference between the two materials is the presence of a large near-surface region in Pb(Zn1/3Nb 2/3)O3 which undergoes a well defined structural transition. The relaxor transition can be interpreted in terms of a random field model where the appropriate universality class is the three-dimensional Heisenberg model with cubic anisotropy. The random field model can be further applied to reconcile previous apparent conflicting interpretations of the lattice dynamics.Neutron scattering is an important tool in studying the structure, lattice vibrations, and spin dynamics in materials. Neutron elastic and inelastic scattering was used in this work to investigate the fluctuations and the structure in the YBa2CuO6+x superconductor as well as the relaxor ferroelectrics Pb(Mg1/3Nb2/3)O 3 and Pb(Zn1/3Nb2/3)O3. The spin fluctuations in the YBa2Cu3O6+x superconductor were studies for x in the underdoped region with x = 0.5 (Tc = 59 K). YBa2Cu 3O6.5 has good structural properties with well ordered oxygen chains. This provides a unique opportunity to study the spin fluctuations in a high-temperature superconductor in the presence of minimal structural disorder. The spin response in the YBa2Cu3O6.5 superconductor has been investigated using both time-of-flight and triple-axis spectrometers up to energy transfers of about 110 meV. The spin spectrum in YBa2Cu3O6.5 is dominated by a strong resonance at 33 meV. The low-energy scattering is characterized by one-dimensional incommensurate scattering with incommensurate peaks displaced along [100] direction. The high-energy fluctuations in the range from ho = 40--100 meV are qualitatively similar to the linear spin-waves measured in the insulator.
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