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High Pressure Single Crystal Neutron Scattering Study Of Magnetic And Fe Vacancy Orders In Tlrb2 Fe4 Se5 Superconductor
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Book Synopsis High-Pressure Single-Crystal Neutron Scattering Study of Magnetic and Fe Vacancy Orders in (Tl,Rb)2 Fe4 Se5 Superconductor by :
Download or read book High-Pressure Single-Crystal Neutron Scattering Study of Magnetic and Fe Vacancy Orders in (Tl,Rb)2 Fe4 Se5 Superconductor written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We investigate the magnetic and iron vacancy orders in superconducting (Tl,Rb)2Fe4Se5 single-crystals by using a high-pressure neutron diffraction technique. Similar to the temperature effect, the block antiferromagnetic order gradually decreases upon increasing pressure while the Fe vacancy superstructural order remains intact before its precipitous disappearance at the critical pressure Pc = 8.3 GPa. Combined with previously determined Pc for superconductivity, our phase diagram under pressure reveals the concurrence of the block AFM order, the √5 × √5 iron vacancy order and superconductivity for the 245 superconductor. Lastly, a synthesis of current experimental data in a coherent physical picture is attempted.
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 Scattering Investigation of the Magnetic Order in Single Crystalline BaFe2As2 by :
Download or read book Neutron Scattering Investigation of the Magnetic Order in Single Crystalline BaFe2As2 written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The magnetic structure of BaFe2As2 was determined from polycrystalline neutron diffraction measurements soon after the ThCr2Si2-type FeAs-based superconductors were discovered. Both the moment direction and the in-plane antiferromagnetic wavevector are along the longer a-axis of the orthorhombic unit cell. There is only one combined magnetostructural transition at ≈140 K. However, a later single-crystal neutron diffraction work reported contradicting results. Here, we show neutron diffraction results from a single-crystal sample, grown by a self-flux method, that support the original polycrystalline work.
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 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 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 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 Magnetic Correlations in High T by :
Download or read book Magnetic Correlations in High T written by and published by . This book was released on 1989 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A review is given of current neutron scattering experiments on La2minus/x/Sr(subscript x)CuO4 and Nd2minus/x/Ce(subscript x)CuO4. Incommensurate magnetic excitations are observed in a high quality single crystal of La/sub 1.85/Sr/sub 0.15/CuO4, which exhibits a sharp superconducting transition at 33 K. The study of magnetic correlations in the electron-superconductor Nd2minus/x/Ce(subscript x)CuO4 is now being carried out. 18 refs., 7 figs.
Book Synopsis Inelastic and Small Angle Neutron Scattering Study of the La2-xSrxCuO4 High-[Tau]c Superconductor in a Magnetic Field by : Raffaele Gilardi
Download or read book Inelastic and Small Angle Neutron Scattering Study of the La2-xSrxCuO4 High-[Tau]c Superconductor in a Magnetic Field written by Raffaele Gilardi and published by . This book was released on 2004 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Inelastic and Small Angle Neutron Scattering Study of the La2-xSrxCuO4 High-Tc Superconductor in a Magnetic Field by : Raffaele Gilardi
Download or read book Inelastic and Small Angle Neutron Scattering Study of the La2-xSrxCuO4 High-Tc Superconductor in a Magnetic Field written by Raffaele Gilardi and published by . This book was released on 2004 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Inelastic and Small Angle Neutron Scattering Study of the La2-xSrxCuO4 High-Τc Superconductor in a Magnetic Field by : Raffaele Gilardi
Download or read book Inelastic and Small Angle Neutron Scattering Study of the La2-xSrxCuO4 High-Τc Superconductor in a Magnetic Field written by Raffaele Gilardi and published by . This book was released on 2004 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Neutron Scattering Studies of the Coexistence of Long-range Magnetic Order and Superconductivity in Dy/sub 1 /sub 2/Mo/sub 6/S/sub 8/ and Tb/sub 1 /sub 2/Mo/sub 6/S/sub 8 by :
Download or read book Neutron Scattering Studies of the Coexistence of Long-range Magnetic Order and Superconductivity in Dy/sub 1 /sub 2/Mo/sub 6/S/sub 8/ and Tb/sub 1 /sub 2/Mo/sub 6/S/sub 8 written by and published by . This book was released on 1978 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Both Dy/sub 1/ /sub 2/Mo/sub 6/S/sub 8/ and Tb/sub 1/ /sub 2/Mo/sub 6/S/sub 8/ are superconducting below T/sub c/ = 2.05 K. Neutron scattering studies show that these compounds in zero applied magnetic field develop long-range antiferromagnetic order (greater than 300 A) at T/sub M/ = 0.4 K and T/sub M/ = 1.0 K, respectively, which does not destroy the superconducting state. Magnetization measurements at temperatures below T/sub M/ suggest the development of ferromagnetic order as the applied magnetic field increases. In the case of Tb/sub 1/ /sub 2/Mo/sub 6/S/sub 8/ the neutron data show long-range ferromagnetic order developing for H greater than or equal to H/sub c2/ = 1.9 kOe where H/sub c2/ is the upper critical field for superconductivity. However, for Dy/sub 1/ /sub 2/Mo/sub 6/S/sub 8/ long-range ferromagnetic order begins to develop at H = 200 Oe, a field much less than H/sub c2/ = 1.2 kOe. As the ferromagnetic intensity increases, the antiferromagnetic intensity decreases. Between H = 200 Oe and H = 1.2 kOe both ferromagnetic and antiferromagnetic order occur with the sample in the superconducting state.
Book Synopsis Single Crystal Neutron Diffraction Study of the Magnetic Phase Diagram of the Heavy Fermion Superconductor UPd2Al@b3@s by :
Download or read book Single Crystal Neutron Diffraction Study of the Magnetic Phase Diagram of the Heavy Fermion Superconductor UPd2Al@b3@s written by and published by . This book was released on 1993 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Neutron Scattering Study of the Magnetic Transition in the Reentrant Superconductor Ho0 6Er0 4Rh4B4 by :
Download or read book Neutron Scattering Study of the Magnetic Transition in the Reentrant Superconductor Ho0 6Er0 4Rh4B4 written by and published by . This book was released on 1979 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A number of different diffraction patterns were obtained with various resolutions. A high-resolution scan of the (101), (110), and (002) peaks at 1.6 and 4.2 K shows that these peaks have very small nuclear components as observed in the 4.2 K data; large magnetic (101) and (110) peaks found at 1.6 K show long-range ferromagnetic order. Analysis of the nuclear and magnetic diffraction peaks shows that the average ordered moment is about 5.0 +- 0.5 .mu./sub B/ at 1.6 K. The temperature dependence of the intensity of the (101) powder peak is also shown. No long-range magnetic scattering is found above 3.60 K. At 3.60 K the magnetic intensity jumps suddenly to a finite value, then increases nearly linearly with temperature to about 2.5 K. Below 2.5 K the intensity rounds off and appears to saturate at about 1.6 K. There are no specific heat anomalies between 0.5 K and 1.6 K. 3 figures. (RWR).
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