1,721,027 research outputs found
Spin dynamics of 3d heavy fermion compound LaMn4Al8
No full textYamasaki et al. have suggested that LaMn4Al8 is a nearly antiferromagnetic metal with linear chains of Mn atoms. The Sommerfeld constant for LaMn4Al8 ?=265 mJ/mol K2 is comparable to values found in other 3d heavy fermions such as (YSc)Mn2 and ?-Mn. We have shown that LaMn4Al8 displays antiferromagnetic order below 15 K. Here we present inelastic neutron scattering data on LaMn4Al8. The magnetic scattering in LaMn4Al8 has two components: a broad inelastic response centred near 30 meV and a narrower quasielastic response whose width and weight change with temperature. We attribute the latter to near-critical spin fluctuations
A study of CeB2C2 using inelastic neutron scattering
No full textInelastic neutron scattering measurements have been carried out to investigate the crystal field (CF) excitations of CeB2C2. The crystal field excitations have large energy widths, indicating strong hybridization between the localized 4f electrons and the conduction electrons. The analysis of the data, based on a crystal field model, gives good agreement with both the measured heat capacity and the saturation magnetization at low temperatures.<br/
Neutron scattering studies of an antiferromagnetic Kondo compound: Ce8Pd24Ga
No full textThe antiferromagnet Ce8Pd24Ga with TN = 3.1 K has been investigated using neutron diffraction, inelastic neutron scattering, electrical resistivity, magnetoresistance and magnetic susceptibility measurements. Rietveld analysis of neutron diffraction data reveals that Ce8Pd24Ga crystallizes in the cubic structure with space group Pmbar 3m. Inelastic neutron scattering (INS) studies show two well-defined crystal-field excitations at 3.2 meV and 12.8 meV. The crystal-field parameters have been estimated from the analysis of INS data. The heat capacity calculated from the crystal-field level scheme shows a Schottky peak at 15 K which agrees well with the reported experimental results. The resistivity exhibits -ln T behaviour at high temperature followed by a peak at 8 K and eventually drops at TN. The peak in the resistivity at 8 K arises due to the combined effect of crystalline electric fields and Kondo interactions. The analysis of the resistivity data in the magnetically ordered state reveals a gap of 16.1 K in the spin-wave spectrum. At 1.8 K the magnetoresistance is positive and it changes to negative at 3 K. The positive magnetoresistance at 1.8 K is consistent with the antiferromagnetic ground state. The negative magnetoresistance shows a scaling behaviour that yields a low-temperature Kondo temperature of 5.8 K. The magnetic susceptibility exhibits Curie-Weiss behaviour between 20 K and 300 K with an effective paramagnetic moment µeff = 2.33 µB and paramagnetic Curie temperature theta(p) = -18.8 K. The present studies reveal that the physical properties of Ce8Pd24Ga are governed by the Kondo, crystal-field and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions
µSR study of CeRu<sub>2</sub>(Ge<sub>1-x</sub>Si<sub>x</sub>)<sub>2</sub> heavy fermion alloys
No full textZero field µSR measurements on CeRu2(Ge1-xSix)2 for x=0, 0.125, 0.25 and 0.5 show damped oscillations in the low-temperature-ordered phases. For x=0.125, 0.25 two distinct regimes are found in the temperature dependence of the oscillation frequency, corresponding to sinusoidally modulated magnetic order and ferromagnetism.<br/
A reduced moment antiferromagnetic Kondo lattice compound: Ce8N24Ga
No full textWe have investigated the antiferromagnetic Kondo lattice compound Ce8Pd24Ga through neutron powder diffraction and zero-field muon spin relaxation measurements. Our neutron diffraction study reveals a commensurate type-C antiferromagnetic structure below TN=3.6 K, with the ordered state magnetic moment of not, vert, similar0.36 ?B/Ce-atom along the cubic left angle bracket1 1 1right-pointing angle bracket direction. The zero-field muon spin relaxation rate exhibits a sharp increase below TN in agreement with antiferromagnetic ordering observed by the neutron diffraction study. The origin of the reduced moment ordering has been discussed in terms of the Kondo effect
A study of the anti-ferromagnetic quadrupolar ordering in (DyB2C2)-B-11 through inelastic neutron scattering
No full textInelastic neutron scattering measurements have been carried out to investigate the crystal field (CF) excitations of DyB2C2 in order to understand the mechanisms of the quadrupolar ordering (TQ) observed at 24.7 K. Our analysis shows that the ground state is made up of nearly degenerate two Kramer doublets forming a ‘quasi-quartet’ ground state. This is consistent with heat capacity measurements, which have shown an estimated entropy of Rln2 at TN (15.3 K) and an additional Rln2 at TQ. A considerable shift and change in the width of the CF excitations and the splitting of the quasi-quartet ground state into two well-resolved doublets below TQ as well as a Zeeman splitting below TN have also been observed.<br/
Letter. Spin-glass order induced by dynamic frustration
No full textSpin glasses are systems whose magnetic moments freeze at low temperature into random orientations without long-range order. It is generally accepted that both frustration and disorder are essential ingredients in all spin glasses, so it was surprising that PrAu2Si2, a stoichiometric compound with a well-ordered crystal structure, was reported to show spin-glass freezing. Here, we report on inelastic neutron scattering measurements of crystal-field excitations, which show that PrAu2Si2 has a singlet ground state and that the exchange coupling is very close to the critical value to induce magnetic order. We propose that spin-glass freezing results from dynamic fluctuations of the crystal-field levels that destabilize the induced moments and frustrate the development of long-range magnetic correlations. This novel mechanism for producing a frustrated ground state could provide a method of testing the concept of 'avoided criticality' in glassy systems
Neutron diffraction and inelastic neutron scattering investigations of the ordered double perovskite Ba2PrIrO6
No full textHigh-resolution neutron-powder diffraction data show that the double perovskite Ba2PrIrO6 is cubic at ambient temperatures in space group Fm m. Below TN=71 K the compound orders antiferromagnetically with magnetic moments of 0.43(2) ?B at 6 K, on both the Pr4+ and the Ir4+ sites, oriented along the cubic a-axis. Inelastic neutron scattering at 105 K reveals a strong peak at 276 meV and a weak transition at 366 meV. The former is consistent with the crystal field splitting of the Pr4+ ground state under the cubic point symmetry, while the latter peak is due to the intermultiplet transition between the ground state and excited state.<br/
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
