Roger Eccleston

Roger Eccleston
Sheffield Hallam University | SHU · Materials and Engineering Research Institute (MERI)

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136
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Publications

Publications (136)
Preprint
We investigate the spin dynamics of the cuprate ladder Sr$_{2.5}$Ca$_{11.5}$Cu$_{24}$O$_{41}$ to elucidate the behavior of its intrinsically doped holes. Combining high-resolution neutron spectroscopy and density matrix renormalization group calculations enables a comprehensive analysis of the collective magnetic dynamics. We find a general absence...
Article
Optimal processing conditions for fabrication of dense single-phase 6L-Ba2CoTeO6 ceramics via the solid-state reaction method were determined. These ceramics possess a room-temperature crystal structure described by the centrosymmetric P3 @#x0305;m space group. Polarized Raman spectroscopy enabled the observation of all the 25 predicted Raman modes...
Article
We present the results of a detailed investigation of the inelastic neutron scattering from diatomic N2, at wave-vector transfers in the range Q = 20–100 Å−1 (1Å = 10−10 m). At intermediate Q, the scattering shows structure arising from the vibrational modes of the molecule, while at large Q the scattering is well described by the impulse approxima...
Article
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Article
Full-text available
The high solid angular coverage of the general materials (GEM) diffractometer at the ISIS pulsed neutron source located at the UK Rutherford Appleton Laboratory offers the capability of obtaining quantitative bulk crystallographic texture data in a 'single shot' within a matter of minutes. This enables the possibility of in situ texture measurement...
Article
Full-text available
We have performed inelastic neutron scattering on the near ideal spin-ladder compound La4Sr10Cu24O41 as a starting point for investigating doped ladders and their tendency toward superconductivity. A key feature was the separation of one-triplon and two-triplon scattering. Two-triplon scattering is observed quantitatively for the first time and so...
Article
We present inelastic neutron scattering measurements of three spin-ladder compounds. All are based on two-dimensional copper oxide layers where the copper ions form two-leg, spin-1/2, spin-ladders. Strong antiferromagnetic interactions couple the spin moments along the legs and rungs of the ladder, weaker higher order four-spin ring exchange terms...
Article
MERLIN is designed to be a high intensity, medium energy resolution spectrometer. As such, it will complement the high-resolution MAPS spectrometer at ISIS. MERLIN will utilise all the latest advances in technology with a supermirror guide to enhance flux as well as 3 m long position-sensitive detectors in a vacuum making it ideal for single-crysta...
Article
Full-text available
Neutron radiography in many cases is the only non-destructive technique available for the analysis of a wide range of samples from metallurgy, materials engineering and materials testing. In this paper the potential of the technique is illustrated for a transient liquid phase (TLP) joint. TLP bonding produces interface free and stress free joints....
Article
TOF spectroscopy is well suited to experiments that involve surveying large ranges in either energy transfer or energy and momentum transfer space. Developments in both instrumentation and experimental techniques have opened up new scientific opportunities and produced some outstanding results to date. These developments show every sign of continui...
Article
Inelastic-neutron-scattering measurements of magnetic response in CeNi have been performed at temperatures between 10 and 300K. Three temperature intervals with different shapes of magnetic response have been observed. The lowest characteristic temperature apparently corresponds to development Ce ion correlations.
Article
We present the results of an inelastic neutron scattering experiment on polycrystalline URhGe. This sample displayed a nearly quasi-elastic type of magnetic scattering indicative of strong hybridization between the 5f states and conduction electrons. This scattering shows no sizable temperature dependence and extends to the highest energies measure...
Article
We report on developments in building a compact neutron spin filter based on metastable optical pumping. The apparatus incorporates a high-power Yb-fibre laser, and polarisations of >70% are now routinely achieved in sealed cells prepared at ISIS. A circulating system has also been constructed and initial results with polarised gas are reported. Ce...
Article
Position sensitive detectors at the ISIS facility largely comprise of a mixture of 3He proportional counters and fibre-coded scintillation detectors based on ZnS/6LiF. The latest developments of these devices at ISIS will be discussed with reference to three ISIS instruments, MERLIN, GEM and ENGIN-X.MERLIN is the new chopper spectrometer now being...
Article
A small shift of magnetic excitation energies is expected when applying pressure on a compound with large magnetostriction. We were able to observe these tiny shifts by inelastic neutron scattering on the giant magnetostriction (GMS) compound TbCu2. The experiments were performed at 4 and 60K using a McWhan pressure cell. The peaks in the spectra w...
Article
A guided tour of ISIS appeared in Neutron News in 1995, ten years after the facility started operating. This article is intended as an update, focusing on the developments that have taken place since then. The period has been an exciting one of expansion for the ISIS facility, its instruments, and user program, which is constantly evolving to meet...
Article
The existence of a wide distribution of low energy excess magnetic states due to topological disorder in a magnetic glass is confirmed experimentally for the case of terbium metaphosphate glasses with compositions in the vicinity of (Tb2O3)0.25(P2O5)0.75. A broad peak with a maximum at 7.5 K is found in the magnetic contribution to the specific hea...
Article
Full-text available
We have studied the effect of Lu substitution on the spin dynamics of the Kondo insulator YbB12 to clarify the origin of the spin-gap response previously observed at low temperature in this material. Inelastic neutron spectra have been measured in Yb1-xLuxB12 compounds for four Lu concentrations x = 0, 0.25, 0.90 and 1.0. The data indicate that the...
Article
Using inelastic neutron scattering, we have measured a range of amorphous forms of ice, including high-density and low-density amorphous ices, in the energy transfer region from 2 to 500 meV (16–4033 cm-1). The measured spectra show that the pressure-produced high-density amorphous ice is significantly different from the two low-density amorphous f...
Article
A special Microsymposium on polarized neutron methods and technologies on existing and future pulsed neutron sources was held at PNCMI-2002. We present the recommendations formulated by three working groups on “Diffraction,” “Inelastic Scattering” and “Reflectometry.” Needs for method development as well as opportunities for novel polarized neutron...
Article
Quasi-elastic and inelastic neutron scattering studies of the quasi-one-dimensional S=2 antiferromagnet MnCl3(C10D8N2) are reported. The quasi-elastic measurements exhibit a broad peak at Q&#440.69 -1, which is consistent with short-range antiferromagnetic coupling between neighboring Mn3+ ions. Inelastic experiments, at 150 mK and Q=0.70 -1, revea...
Article
The influence of the coherence breakdown in the Yb sublattice on the excitation spectra of YbB12-based systems and the characteristics of the crystal field potential have been studied by inelastic neutron scattering on Yb0.75Lu0.25B12 and Yb0.9Er0.1B12 samples. The crystal field potential has been determined by use of the Er3+ ions as a sensor. The...
Article
We present a design for a low-energy-transfer, 1-20 meV, multi-chopper (MC) spectrometer, intended for the new second target station (TSII) at ISIS. At present, low-energy MC spectrometers exist only on steady-state sources, but our results show they are better suited to a pulsed spallation source.
Article
We report for the first time, the observation of non-Fermi-liquid scaling behavior in an elemental paramagnetic metal. Both the dynamical susceptibility and the resistivity of beta-Mn are shown to display non-Fermi-liquid scaling over a relatively large temperature range at ambient pressure. The temperature dependence of the resistivity in beta-Mn...
Article
The physical properties of TmxLa1-xTe for x=0.05 and 0.5 have been investigated by electrical resistivity, magnetic susceptibility, magnetization, and specific heat measurements and by inelastic neutron scattering. It is shown that the Tm ion experiences a large crystalline electric field (CEF) in a metallic environment at a low concentration of x=...
Chapter
Inelastic neutron scattering experiments have been performed in order to study the wave vector dependence of the magnetic fluctuation in YBa2C3O6.7 (Tc=68 K) and YBa2CU3O7−δ (Tc=93 K). Incommensurability of spin dynamics was clearly observed for the underdoped compound. The incommensurate peaks appear at (1/2±δ, 1/2, 0) and (1/2, 1/2±δ, 0), with th...
Article
Full-text available
Neutron spectroscopic measurements of the magnetic excitations in PrO2 reveal (1) sharp peaks characteristic of transitions between levels of the 4f(1) configuration of Pr4+ split by the cubic crystal field, and (2) broad bands of scattering centered near 30 and 160 meV. We present a simple model based on a vibronic Hamiltonian that accounts for th...
Article
Neutron spectroscopic measurements of the magnetic excitations in PrO2 reveal (1) sharp peaks characteristic of transitions between levels of the 4f(1) configuration of Pr4+ split by the cubic crystal field, and (2) broad bands of scattering centered near 30 and 160 meV. We present a simple model based on a vibronic Hamiltonian that accounts for th...
Preprint
Full-text available
Neutron spectroscopic measurements of the magnetic excitations in PrO$_2$ reveal (1) sharp peaks characteristic of transitions between levels of the $4f^1$ configuration of Pr$^{4+}$ split by the cubic crystal field, and (2) broad bands of scattering centred near 30 meV and 160 meV. We present a simple model based on a vibronic Hamiltonian that acc...
Article
Using a pulsed neutron source we have been able to observe inelastic signals at high energies from the ladders of La6Ca8Cu24O41. These signals constitute the magnon branch (∼30<~E<~∼190 meV) for the lowest triplet excitation. A fit to a theory including a coupling along the leg (Jleg) and rung (Jrung) alone gives the value Jleg/Jrung∼2 that is not...
Article
We studied the magnetic excitations from the S=1/2 two-leg ladders in La <sub> 6 </sub> Ca <sub> 8 </sub> Cu <sub> 24 </sub> O <sub>41</sub>. In order to understand the full dispersion of the magnon branch for the lowest triplet excitation, effects of the four-spin and the next-nearest-neighbor (diagonal) exchange interactions are analyzed. We also...
Article
UNiSn transforms from a paramagnetic semiconductor to an antiferromagnetic metal at TN=43K. We have made a detailed neutron scattering study of UNiSn and find well-defined magnetic excitations in the metallic phase, at 10 and 35meV, with no evidence of excitations at higher energies. The excitations persist in the semiconducting phase, but their li...
Article
Full-text available
Low-temperature specific heat measurements on NdNiO3 evidence the onset of Nd cooperative ordering at T-N2=0.77 K. Because of the particular arrangement of the Ni magnetic moments, half of the Nd ions have an antiferromagnetically compensated environment while the other half have a noncompensated one. We show that both types of Nd ions are affected...
Article
We report measurements of the temperature dependence of the sound attenuation and the fractional change in sound velocity for the glass (G) and orientational-glass (OG) phases of polymorphic ethanol. Strikingly similar behaviors are found for both phases despite the OG’s underlying crystal (bcc) lattice. Such similarity, which is also revealed in d...
Article
The structure of the (SrxCa1−x)14Cu24O41 series contains both Cu2O3 spin-ladder layers and CuO2 spin chains. Previous measurements on the undoped sample (x=1) showed all the holes were located on the chains, with the magnetic Cu2+ ions on the chain forming a well-defined dimer configuration. We have performed inelastic neutron scattering on a singl...
Article
The dynamic magnetic response of intermediate valence Yb11B12 has been studied by inelastic neutron scattering on the HET time-of-flight spectrometer, with incident energies Ei=200meV at T=15K and Ei=80meV at T=15–160K. The low-temperature magnetic response spectrum has a fine structure with a cut off at about 40meV. No quasielastic magnetic scatte...
Article
The compound Ca_xSr_14-xCu_24O_41 contains both spin ladders and alternating spin chains. The magnetic excitations on the ladders are well understood and can be described by a ladder model. For the x=0 compound the chain excitations can be described by an alternating ferro-antiferromagnetic chain. Our neutron scattering studies, on a sample heavily...
Article
Inelastic neutron scattering (INS) was used to study the magnetic excitations in the compounds Gd1-xYxFe2 and Gd2-xYxFe14B. Three inelastic magnetic lines were observed in the INS spectra of these compounds, the two smaller lines appearing as shoulders to the main line. From the concentration-dependent shift of the dominant magnetic line we have ob...
Article
The New Perspectives in Neutron and Muon Science is now in its third year and is becoming something of a traditional precursor to the UK Neutron and Muon Beam Users Meeting. This year's meeting was hosted by the University of Durham and was held in the Chemistry Department from September 8–9, 1999. with John Evans doing an excellent job with the lo...
Article
The rare-earth based nickelates RNiO3 (R=Pr, Nd, Sm, Eu, and Pr1−xLax, 0<~x<~0.7) were studied by inelastic neutron scattering. Energy splittings due to the crystalline-electric-field (CEF) interaction at the R3+ site within the electronic ground-state J multiplet (for R=Pr, Nd, and Pr1−xLax) as well as within the two lowest-lying J multiplets (for...
Article
Full-text available
Time-of-flight inelastic neutron scattering experiments on the archetype Kondo-insulator compound YbB12 are reported. At the minimum temperature of T=15K, the magnetic response clearly shows a spin-gaplike behavior below 10 meV. Above this energy, the spectrum consists of three main components at 15, 20, and 38 meV. Above 40 K, substantial quasiela...
Article
The existence of a wide distribution of low energy excess magnetic states due to topological disorder in a magnetic glass is confirmed experimentally for terbium metaphosphate glasses with compositions in the vicinity of (Tb2O3)0.25(P2O5)0.75. A broad peak with a maximum at 7.5K is found in the magnetic contribution to the specific heat; this has i...
Article
We report on spin dynamics in the highly hole doped quasi-one-dimensional cuprate Sr0.73CuO2 measured by inelastic neutron scattering. An excitation mode with peaks at E=10 and 17.5 meV is observed in the spectrum. Additional magnetic scattering remains present up to E∼25meV. These features are due to excitations of dimerized antiferromagnetic chai...
Article
High energy inelastic neutron scattering measurements were performed in order to elucidate the wave vector and energy dependence of the spin dynamics in YBa2Cu3O6.7 (Tc=68 K) and YBa2Cu3O7 (Tc=93 K) by using pulsed neutron techniques. The incommensurability of spin dynamics was clearly observed for the under-doped compound. The peaks appear at (1/2...
Article
Inelastic neutron scattering (INS) was used to study the magnetic excitations of Sm3+ ions in the archtypical hardmagnetic material SmCo5. Two inelastic magnetic lines were observed that can be interpreted as: (i) a transition within the ground state J-multiplet 6H5/2 and (ii) a transition from the ground state to the first excited J-multiplet 6H7/...
Article
Vibrational spectra of high-pressure phase ice VIII have been studied by inelastic neutron scattering over a wide energy transfer range, including external intermolecular and internal intramolecular modes up to 500 meV. It was clearly shown that the stretching intramolecular modes in ice VIII exhibit a narrow peak at an energy of 426 meV (or 3436 c...
Article
We report very high-energy paramagnetic scattering from the compound CeFe2 having a spectral form consistent with a localised, strongly hybridized 4f-state with the highest characteristic energy TK observed to-date for any alpha-Ce-like system, viz. ~570 meV (i.e. 6500 K). In addition, the integrated spectral intensity of the broad response corresp...
Article
We summarise our UxY1-xPd3 inelastic neutron scattering experiments and present new neutron diffraction results for a single crystal of U0.45Y0.55Pd3. Long-range antiferromagnetic order is unambiguously observed below TN=22.5 K. In contrast, no long-range order is found in polycrystalline samples of U0.37Y0.63Pd3, U0.28Y0.72Pd3 and U0.2Th0.25Y0.55P...
Article
High energy magnetic excitations in the Kondo compound with the ε-TiNiSi type crystal structure, CeRhSb, were observed by inelastic neutron scattering. The magnetic excitation spectrum at 17K shows a broad inelastic peak which is well reproduced by the Lorentzian spectral function centred at E0=32±4meV with a half width of Γ∼E0.
Article
Full-text available
We have investigated the compounds and with the aim of establishing the magnetic energy levels and wavefunctions of the and ions. We report neutron inelastic scattering, specific heat capacity and susceptibility measurements, and analyse the data in two stages to obtain a model for the crystal field acting on the and ions. First we find the best mo...
Article
The second “New Perspectives in Neutron and Muon Science” meeting was held at Cosener's House in Abingdon from September 23–24, 1998. The objective of this meeting, organized by the Neutron Scattering Group of the Institute of Physics and The Royal Society of Chemistry, and co'sponsored by ISIS and EPSRC, was to provide Ph.D. students and young pos...
Article
The rare-earth based nickelates RNiO3 (R = Pr, Nd, Sm, Eu, and Pr1-xLax, 0≤x≤0.7) were studied by inelastic neutron scattering. Energy splittings due to the crystalline-electric-field (CEF) interaction at the R3+ site within the electronic ground-state J multiplet (for R = Pr, Nd, and Pr1-xLax) as well as within the two lowest-lying J multiplets (f...
Article
Inelastic neutron scattering (INS) has been used to study the exchange interaction in polycrystalline samples of GdMn2Si2, GdMn2Ge2, GdMn6Sn6 and Gd6Mn23. Direct values of the molecular fields experienced by the Gd moments were obtained from the position of the dominant transition at low momentum transfer in the INS spectra. By using a simple spin...
Article
We have performed inelastic neutron scattering on a single crystal sample of Sr14Cu24O41 to study the spin dynamics of the Cu2O3 spin ladder layers and CuO2 chains. Our data are best fitted with a dispersion which has a spin gap of 32.5+/-0.1 meV and a maximum of 193.5+/-2.4 meV, consistent with a coupling along the ladders, J∥ = 130 meV and a rung...
Article
We have measured the inelastic-neutron-scattering response of UPdSn using the HET and PHAROS spectrometers at the ISIS and LANSCE facilities, respectively. UPdSn shows some quasielastic scattering, which may be attributed to the hybridization of the 5f-electrons with the conduction electrons. We also find a clear excitation around 40 meV above 40 K...
Article
Full-text available
An inelastic neutron scattering study was performed on a Zn-substituted spin-1/2 Heisenberg 2-leg ladder compound Sr(Cu1-x Znx)2O3 (x < 0.04) to investigate nonmagnetic impurity effects on the quantum spin system with a large spin gap of approximately ~400 K. The magnitude of the spin gap was found to be independent of Zn concentration, 33 meV, whi...
Article
Full-text available
The crystalline electric-field (CEF) excitations in the series of UxY1-xPd3 pseudobinary compounds with x=0.45,0.37,0.28,0.20 have been measured using inelastic neutron scattering. Two excitations are found in each compound at energy transfers ~37 meV and ~3 meV that are increasingly hybridized as the uranium concentration is reduced. For U0.45Y0.5...
Article
Nonmagnetic impurity effects on a two-leg quantum spin ladder with a large spin gap of about 400 K were investigated. Surprisingly, only a few % of impurity was found to drive the host gapless and antiferromagnetically ordered at a composition-dependent temperature below 10 K.
Article
We have studied the magnetic behaviour of the alloy Er91.6%Tm8.4% using ultrasound, SQUID and neutron-scattering measurements. We have found that below 40 K the magnetic structure is very similar to the magnetic phase observed between 52 and 18 K in Er. However, high-order commensurate structures, which are stable over no more than approximately 2...
Article
We have performed inelastic neutron scattering on a single crystal sample of Sr14Cu24O41 to study the spin dynamics of the Cu2O3 spin ladder layers and CuO2 chains. Our data are best fitted with a dispersion which has a spin gap of 32.50.1 meV and a maximum of 193.52.4 meV, consistent with a coupling along the ladders, J|| = 130 meV and a rung coup...
Article
The UK Neutron and Muon User meeting was held from September 24–25, 1997 at the Rutherford Appleton Laboratory. This meeting, organized by the EPSRC and chaired by Bill Stirling, provided a forum for users of ISIS and the ILL to air their views about all aspects of the performance of the two facilities, and to suggest andcomment on future developme...
Article
Approximately fifty young researchers of a wide variety of ages converged on Cosener's House in Abingdon for the “New Perspectives in Neutron and Muons Science: A Young Researchers Meeting” held from September 23–24, 1997. The object of this meeting, organized by the Neutron Scattering Group of the Institute of Physics and The Royal Society of Chem...
Article
We report observations of very high-energy scattering from CeRu2(T ∼ 6.2 K) relative to LaRu2(Tc ∼ 4.4 K). The spectral form and density of the magnetic response suggests that the 4f electron in CeRu2 is essentially localised with a 4f-occupancy of ∼ 0.75 (± 0.1). The magnitude of the characteristic energy of ∼ 510 (± 50) meV deduced from a fit usi...
Article
Inelastic magnetic neutron scattering has been used to determine the energy of the 4 A 2→4 T 2 transition in CoAl2O4 spinel and the δ1 transition in Co2[Al4Si5]O18 cordierite. The observed crystal field splitting in Co-spinel is 485 meV (3900 cm−1), which corresponds to a crystal field stabilization energy of 56.2 kJmol−1. The transition energy of...
Article
Inelastic neutron scattering spectra were measured for amorphous ice H2O and D2O produced by low-temperature and low-rate vapor deposition. The data show that the deposition produced the low-density amorphous form of ice, i.e., the high-density amorphous ice observed by x-ray [A. H. Narten, C. G. Venkatesh, and S. A. Rice, J. Chem. Phys. 64, 1106 (...
Article
Measurements of magnetic susceptibility, specific heat and inelastic neutron scattering were performed on a Zn-substituted spin-12 Heisenberg 2-leg ladder compound Sr(Cu1−xZnx)2O3 (x ≤ 0.08) to investigate nonmagnetic impurity effects on the quantum spin system with a large spin gap of about ∼ 400 K. A clear anomaly attributed to the onset of antif...
Article
Inelastic neutron scattering has been employed to search for the crystalline-electric-field (CEF) transitions in the infinite-layer (IL) Sr1−xNdxO2 compounds produced by high-pressure technique. For the first time we have been able to observe the complete energy spectrum of the ground state J-multiplet of Nd3+ in the IL phase and to determine the C...
Article
We present magnetic resonance measurements on the S = 12 spin ladder systems (VO)2P2O7 (two legs), on the cuprates SrCu2O3 (two legs) and Sr2Cu3O5 (three legs). The measurements were performed in the frequency range 35–400 GHz at temperatures down to 1.5 K and in magnetic fields up to 14 T.
Article
We report neutron-scattering measurements on the heavy-Fermion systems Ce(In1-xSnx)3 and Ce(Pt1-xRhx)2. For x = 0, the pure compounds CeIn3 and CePt2 order antiferromagnetically at 10.2 and 1.7 K, respectively. Above these temperatures, in the paramagnetic phase, they show a quasi-elastic central 'peak' as well as a crystal-field excitation Γ7 → Γ8...
Article
Due to their rather simple crystal structure, the infinite-layer (IL) compounds have attracted much interest as a favorable system for the study of mechanisms of the electron or hole doping of the CuO2 planes in the high-Tc superconductors. Crystalline electric field (CEF) investigation of high-Tc superconductors provides direct evidence of the cha...
Article
Due to their rather simple crystal structure, the infinite-layer (IL) compounds have attracted much interest as a favorable system for the study of mechanisms of the electron or hole doping of the CuO2 planes in the high-Tc superconductors. Crystalline electric field (CEF) investigation of high-Tc superconductors provides direct evidence of the cha...
Article
Heisenberg spin ladders offer valuable insight into the behaviour of low dimensional magnetic systems, representing an intermediate stage between one dimensional spin chains and two dimensional lattices. We have studied the spin dynamics of the spin ladder material (VO)2P2O7 by inelastic neutron scattering and have found that the observed scatterin...
Article
We report neutron-scattering measurements on the heavy-Fermion systems Ce(In1−xSnx)3 and Ce(Pt1−xRhx)2. For x = 0, the pure compounds CeIn3 and CePt2 order antiferromagnetically at 10.2 and 1.7 K, respectively. Above these temperatures, in the paramagnetic phase, they show a quasi-elastic central ‘peak’ as well as a crystal-field excitation Γ7 → Γ8...
Article
The weak quasi-elastic magnetic response of the spin ladder compound (VO)2P2O7 is consistent with the scaling form ω±αF(ω/T) where the power α is given by the temperature dependence T−α of the static susceptibility at low temperatures.
Article
We report a preliminary study of the Pr3+ ground-state multiplet of Pr2NiO4. The crystal field energy levels are determined from neutron scattering and specific heat data, and an analysis is presented in terms of an approximate tetragonal crystal field model. The low-temperature magnetic properties of Pr3+ are governed by two singlets of Γ1 and Γ2...
Article
We have used inelastic neutron scattering to study the magnetic excitations in CuO, a quasi 1-D antiferromagnet, along the chain direction, [ζ, 0, ]. The low-energy excitations can be described adequately by linear spin wave theory, but at high energies the magnetic scattering exhibits characteristics of the spinon model.
Article
We report measurements of the low-temperature ground-state (2F52) paramagnetic spectral response of the compounds CeRh2 and Ce(Rh0.73Pt0.27)2. Both compounds show broad lorentzian-like, single-ion spectral response with characteristic energies of ∼ 114 (± 8) and ∼ 63 (± 5) meV, respectively. The lower magnitude of the characteristic energy for the...
Article
The spin dynamics of the 1D antiferromagnetic Heisenberg system Y2BaNi1-xZnxO5 has been investigated by thermal (for x = 0) and cold (for x = 0.01 and 0.03) neutron scattering. The former set of measurements enables us to study the temperature dependence of the transitions from the ground state to states above the Haldane gap. The latter, low incid...
Article
We present neutron diffraction and crystal field (CF) spectroscopy results obtained for the electron-doped superconductor precursor material Nd2-x-yCexLayCuO4 (0 <= x <= 0.2; y = 0.5, 1). Samples were prepared via a sol-gel method. The lattice constants as a function of Ce-doping show the well-known behavior common to this class of compounds, i.e....
Article
URhAl is a ferromagnet (TC = 27 K) with a moment of 1μB per mole directed parallel to the unique hexagonal axis of the structure. The material is known to exhibit an enormous anisotropy, which is thought, in part, to arise from the hybridization of the U 5f with the Rh 4d electrons. We have performed measurements on a large polycrystalline sample a...
Article
We present neutron diffraction and crystal field (CF) spectroscopy results obtained for the electron-doped superconductor precursor material Nd2-x-yCexLayCuO4 (0
Article
Samples of the electron-doped superconductor precursor Nd2-x-yCexLayCuO4 with 0 less than or equal to 4 less than or equal to 0.2 and y=0.5, I have been synthesized with a sol-gel method. While the as-prepared samples are in the normal state, oxygen reduction results in superconducting samples. The dependence of T-c upon Ce-doping x and oxygen cont...
Article
We present experimental results of magnetic susceptibility, magnetization and magnetic resonances on the spin ladder system vanadyl pyrophospate [(VO)2P2O7]. In this system a spinware excitation gap of the order of EG = 50 K was observed with inelastic neutron scattering experiments at the boundary of the Brillouin zone. Our measurements were perfo...
Article
Calorimetric and time-of-flight neutron diffraction experiments are used to establish thermodynamic and structural features of a Cr+0.3 at.% Ru alloy crystal as it undergoes a commensurate-to-incommensurate spin-density-wave (CDSW - ICDSW) phase transition. Both methods confirm the first-order character of the transition. The calorimetric measureme...
Article
We have performed inelastic-neutron-scattering and dc susceptibility measurements on a polycrystalline sample of (Sr0.8Ca0.2)14Cu24O41, which has a complex crystal structure comprising alternating layers containing isolated CuO2 chains and Cu2O3 two-legged ladders. The observed excitation spectrum is consistent with a spin gap for the ladder of 35...
Article
Inelastic neutron scattering measurements on cubic U3Ni3Sb4 reveal well defined crystal field and spin-orbit excitations, consistent with a U4+ 5f2 configuration of the uranium ion. The magnetic ground state is a crystal field singlet. U3Cu3Sn4 shows a broad inelastic response extending out to 70 meV, consistent with moderately strong hybridisation...
Article
The magnetic phase diagram of the Gd - Lu alloy system has been studied in the multicritical region using ultrasound velocity and attenuation measurements and neutron diffraction. A phase diagram has been drawn up on the basis of these measurements. The phase diagram has much in common with that of Gd - Y including the existence of a ferro I phase...
Article
The magnetic excitations in two-dimensional percolating Ising-type antiferromagnets, Rb2CocMg1-cF4 (c=0.60 and 0.70), were studied by pulsed-neutron scattering. The peaks due to Ising-cluster excitations were clearly observed far above T N. Their intensities exist even at 5T N and 2T N for c=0.60 and 0.70, respectively. This reveals that the charac...
Article
We have determined characteristic Kondo energies of the 2F5/2 and 2F7/2 spin-orbit states of Ce in the compound CePd3 using epithermal neutrons. They are ∼50 and ∼90 meV, respectively. Kramers-Kronig and moment sum-rule integrals together help to ascertain that the low-temperature magnetic response for the ground state (2F5/2) is closely (and almos...
Article
We have performed inelastic neutron scattering (INS) experiments to study the spin dynamics and search for crystalline-electric-field (CEF) excitations in the antiferromagnetic heavy-fermion superconductor 0953-8984/8/11/012/img9. The low-energy-transfer spectra are predominantly characterized by a quasielastic Lorentzian (weighted by the detailed...
Article
Neutron intermultiplet spectroscopy has been used to re-examine UPd3 and UPt3 at 17 K. In UPd3, the 3H4 → 3F2 transition is observed at 395 meV, confirming a localised 5f2 state for the uranium ions. In the heavy fermion compound UPt3, only a small trace of this transition remains, indicating that the 5f electrons in this material are of a predomin...
Article
We have performed inelastic-neutron-scattering and dc susceptibility measurements on a polycrystalline sample of (Sr0.8Ca0.2)14Cu24O41, which has a complex crystal structure comprising alternating layers containing isolated CuO2 chains and Cu2O3 two-legged ladders. The observed excitation spectrum is consistent with a spin gap for the ladder of 35...
Article
Inelastic neutron scattering (INS) has been used to study the exchange interactions in polycrystalline samples of GdFe2, GdFe3, Gd3Lu3Fe23, Gd2Fe14B, Gd2Fe14C, Gd2Fe17, GdFe10Si2 and GdFe10.6V1.4. Direct values of the molecular fields experienced by the Gd moments and — by using a simple spin wave model — the GdFe exchange constants in these compo...
Article
Paramagnetic spectral response from CeNi2 measured with epithermal neutrons is found to be consistent with single-ion form with a characteristic (Kondo) energy of ∼130(±10) meV representing the average value from fits to two different single-ion spectral functions. The magnitude of the characteristic energy is in good agreement, via Fermi-liquid re...
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Inelastic neutron scattering measurements on cubic U3Ni3Sb4 reveal well defined crystal field and spin-orbit excitations, consistent with a U4+ 5f2 configuration of the uranium ion. The magnetic ground state is a crystal field singlet. U3Cu3Sn4 shows a broad inelastic response extending out to 70 meV, consistent with moderately strong hybridisation...
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The quaternary compound ErNi2B2C becomes superconducting with a critical temperature of 9 K. DC magnetisation indicates the presence of magnetic ordering of the Er moments at ≈ K. Specific heat measurements show a Schottky anomaly around 45 K with a magnitude of 10 J mol K−1 which agrees well with our model for the crystal-field scheme and neutron...
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Inelastic neutron scattering has been employed to study the crystalline-electric-field (CEF) excitations of Sm3+ ions in SmBa2Cu3O7. We have been able to assign the energetic ordering of all the three and four CEF states in the ground-state and first-excited J multiplets 6H5/2 and 6H7/2, respectively. A set of CEF parameters was derived which excel...