Elastic Neutron-scattering Experiments Research Articles

Suppression of ferromagnetism of CeTiGe3by V substitution

The crystallographic structure, magnetization, specific heat, and electrical resistivity of polycrystalline CeTi${}_{1\ensuremath{-}x}$V${}_{x}$Ge${}_{3}$ ($0\ensuremath{\le}x\ensuremath{\le}0.42$ and $x$ $=$ 1) have been studied. CeTiGe${}_{3}$ has been reported as one of the rare ferromagnetic Kondo systems with a Curie temperature ${T}_{c}$ $=$ 14 K. We present a detailed study of the low-temperature properties on this compound, including magnetization, specific heat, and electrical resistivity in magnetic fields up to 5 T. Elastic neutron-scattering experiments confirm ferromagnetic and exclude ferrimagnetic order of CeTiGe${}_{3}$. Analysis of the specific heat gives evidence of a strong magnetic anisotropy in this system as evidenced by a gap. Replacing Ti by V reduces ${T}_{c}$, with ${T}_{c}\ensuremath{\rightarrow}0$ for $x\ensuremath{\approx}0.35$, suggesting a possible ferromagnetic quantum critical point.

Change of antiferromagnetic structure near a quantum critical point inCeRh1−xCoxIn5

The elastic neutron-scattering experiments were carried out on the solid solutions ${\text{CeRh}}_{1\ensuremath{-}x}{\text{Co}}_{x}{\text{In}}_{5}$ to clarify the nature of the antiferromagnetic (AF) state in the vicinity of the quantum critical point: ${x}_{c}\ensuremath{\sim}0.8$. The incommensurate AF order with the wave vector of ${q}_{h}=(1/2,1/2,\ensuremath{\sim}0.3)$ observed in pure ${\text{CeRhIn}}_{5}$ is weakly suppressed upon doping with Co, and a commensurate ${q}_{c}=(1/2,1/2,1/2)$ and an incommensurate ${q}_{1}=(1/2,1/2,\ensuremath{\sim}0.42)$ AF structures evolve at intermediate Co concentrations. The AF orders with ${q}_{c}$ and ${q}_{1}$ are enhanced at $x=0.7$, and furthermore, the ${q}_{h}$ AF order vanishes. These results suggest that the AF correlations with the ${q}_{c}$ and ${q}_{1}$ modulations are significantly enhanced in the intermediate $x$ range, and may be connected with the evolution of the superconductivity observed above $x\ensuremath{\sim}0.3$.

The Influence of Solvent Composition on Global Dynamics of Human Butyrylcholinesterase Powders: A Neutron-Scattering Study

A major result of incoherent elastic neutron-scattering experiments on protein powders is the strong dependence of the intramolecular dynamics on the sample environment. We performed a series of incoherent elastic neutron-scattering experiments on lyophilized human butyrylcholinesterase (HuBChE) powders under different conditions (solvent composition and hydration degree) in the temperature range from 20 to 285 K to elucidate the effect of the environment on the enzyme atomic mean-square displacements. Comparing D 2O- with H 2O-hydrated samples, we were able to investigate protein as well as hydration water molecular dynamics. HuBChE lyophilized from three distinct buffers showed completely different atomic mean-square displacements at temperatures above ∼200 K: a salt-free sample and a sample containing Tris-HCl showed identical small-amplitude motions. A third sample, containing sodium phosphate, displayed highly reduced mean-square displacements at ambient temperature with respect to the other two samples. Below 200 K, all samples displayed similar mean-square displacements. We draw the conclusion that the reduction of intramolecular protein mean-square displacements on an Ångstrom-nanosecond scale by the solvent depends not only on the presence of salt ions but also on their type.

Reply to “Comment on ‘Magnetic field effects on neutron diffraction in the antiferromagnetic phase ofUPt3’ ”

Fak, van Dijk and Wills (FDW) question our interpretation of elastic neutron-scattering experiments in the antiferromagnetic phase of UPt_3. They state that our analysis is incorrect because we average over magnetic structures that are disallowed by symmetry. We disagree with FDW and reply to their criticism. FDW also point out that we have mistaken the magnetic field direction in the experiment reported by N. H. van Dijk et al. [Phys. Rev. B 58, 3186 (1998)]. We correct this error and note that our previous conclusion is also valid for the correct field orientation.

Magnetic field effects on neutron diffraction in the antiferromagnetic phase ofUPt3

We discuss possible magnetic structures in UPt$_3$ based on our analysis of elastic neutron-scattering experiments in high magnetic fields at temperatures $T<T_N$. The existing experimental data can be explained by a single-{\bf q} antiferromagnetic structure with three independent domains. For modest in-plane spin-orbit interactions, the Zeeman coupling between the antiferromagnetic order parameter and the magnetic field induces a rotation of the magnetic moments, but not an adjustment of the propagation vector of the magnetic order. A triple-{\bf q} magnetic structure is also consistent with neutron experiments, but in general leads to a non-uniform magnetization in the crystal. New experiments could decide between these structures.

Enhancement of static antiferromagnetic correlations by magnetic field in a superconductorLa2−xSrxCuO4withx=0.12

Elastic neutron-scattering experiments have been performed to study effects of high magnetic field on static antiferromagnetic correlations coexisting with the superconductivity in ${\mathrm{La}}_{1.88}{\mathrm{Sr}}_{0.12}{\mathrm{CuO}}_{4}$ ${(T}_{c}=12\mathrm{K}).$ Under the field applied perpendicular to the ${\mathrm{CuO}}_{2}$ plane its superconductivity is severely suppressed at 10 T. The intensity of incommensurate elastic magnetic peaks around the (\ensuremath{\pi},\ensuremath{\pi}) point is, on the other hand, significantly increased at 10 T by as much as 50% of that of 0 T.

Effect of Pressure on Tiny Antiferromagnetic Moment in the Heavy-Electron CompoundURu2Si2

We have performed elastic neutron-scattering experiments on the heavy-electron compound URu_2Si_2 for pressure P up to 2.8 GPa. We have found that the antiferrmagnetic (100) Bragg reflection below T_m ~ 17.5 K is strongly enhanced by applying pressure. For P < 1.1 GPa, the staggered moment mu_o at 1.4 K increases linearly from ~ 0.017(3) mu_B to ~ 0.25(2) mu_B, while T_m increases slightly at a rate ~ 1 K/GPa, roughly following the transition temperature T_o determined from macroscopic anomalies. We have also observed a sharp phase transition at P_c ~ 1.5 GPa, above which a 3D-Ising type of antiferromagnetic phase (mu_o ~ 0.4 mu_B) appears with a slightly reduced lattice constant.

Elastic neutron-scattering experiments at the Geesthacht Neutron Facility (GeNF)

The Geesthacht Neutron Facility (GeNF) comprises experimental facilities for elastic neutron scattering for materials research and engineering problems as well as for environmental research purposes at the research reactor FRG-1. The experimental facilities for elastic neutron-scattering experiments at GeNF, most of which can be optimally used with polarized neutrons, will be presented. They are open to national and international users from universities and other research institutes at no cost.

Evidence for a magnetic-polaron state in the low-carrier system CeP.

Elastic neutron-scattering experiments performed in the low-carrier system CeP show interesting magnetic diffraction patterns under a magnetic field. They can be explained by the stacking of the ferromagnetically coupled ${\mathrm{\ensuremath{\Gamma}}}_{8}$ double Ce layers among the antiferromagnetically coupled ${\mathrm{\ensuremath{\Gamma}}}_{7}$ layers with a period of eleven Ce layers along the field direction, even though the crystal-field level energy of ${\mathrm{\ensuremath{\Gamma}}}_{8}$ is 160 K. The result gives direct evidence for the existence of the magnetic-polaron state in CeP proposed by Kasuya et al.

Maximum entropy as a tool for the determination of the c-axis profile of layered compounds

A simple procedure for the determination of the structure normal to the basal plane of layered compounds based on the now ubiquitous maximum-entropy method is presented. It is illustrated by the analysis of room-temperature (001) elastic neutron-scattering experiments performed on two graphite intercalation compounds, stage 3 C 44.6 MoCl 5 and stage 1 KC 24 (ND 3 ) 4.3 . The former example is quite simple, requiring only a crude heuristic model to determine the structure-factor phases. The latter shows good sensitivity to the orientation of the ND 3 threefold axis with respect to the basal plane, thus providing its first direct determination