arXiv subjects

A. J. Schultz

Publications and source records attributed to A. J. Schultz.

5 recordsLinked to original sources

arXiv2011

Structural, electronic, magnetic, and thermal properties of single-crystalline UNi0.5Sb2

We studied the properties of the antiferromagnetic (AFM) UNi0.5Sb2 (TN \approx 161 K) compound in Sb-flux grown single crystals by means of measurements of neutron diffraction, magnetic susceptibility (χ), specific heat (Cp), thermopower (S), thermal conductivity (κ), linear thermal expansion (ΔL/L), and electrical resistivity (ρ) under hydrostatic pressures (P) up to 22 kbar. The neutron diffraction measurements revealed that the compound crystallizes in the tetragonal P42/nmc structure, and the value of the U-moments yielded by the histograms at 25 K is \approx 1.85 \pm 0.12 μB/U-ion. In addition to the features in the bulk properties observed at TN, two other hysteretic features centered near 40 and 85 K were observed in the measurements of χ, S, ρ, and ΔL/L. Hydrostatic pressure was found to raise TN at the rate of \approx 0.76 K/kbar, while suppressing the two low temperature features. These features are discussed in the context of Fermi surface and hybridization effects.

cond-mat.str-el↗

arXiv2010

Magnetic Order in TbCo2Zn20 and TbFe2Zn20

We report neutron diffraction studies of TbCo$_2$Zn$_{20}$ and TbFe$_2$Zn$_{20}$, two isostructural compounds which exhibit dramatically different magnetic behavior. In the case of TbCo$_2$Zn$_{20}$, magnetic Bragg peaks corresponding to antiferromagnetic order are observed below $T_N$ $\approx$ 2.5 K with a propagation vector of (0.5 0.5 0.5). On the other hand, TbFe$_2$Zn$_{20}$ undergoes a ferromagnetic transition at temperatures as high as 66 K which shows a high sensitivity to sample-to-sample variations. Two samples of TbFe$_2$Zn$_{20}$ with the same nominal compositions but with substantially different magnetic ordering temperatures ($T_c$ $\approx$ 51 and 66 K) were measured by single crystal neutron diffraction. Structural refinements of the neutron diffraction data find no direct signature of atomic site disorder between the two TbFe$_2$Zn$_{20}$ samples except for subtle differences in the anisotropic thermal parameters. The differences in the anisotropic thermal parameters between the two samples is likely due to very small amounts of disorder. This provides further evidence for the extreme sensitivity of the magnetic properties of TbFe$_2$Zn$_{20}$ to small sample variations, even small amounts of disorder.

cond-mat.str-el↗

arXiv2007

Magnetic and orbital ordering in the spinel MnV2O4

Neutron inelastic scattering and diffraction techniques have been used to study the MnV2O4 spinel system. Our measurements show the existence of two transitions to long-range ordered ferrimagnetic states; the first collinear and the second noncollinear. The lower temperature transition, characterized by development of antiferromagnetic components in the basal plane, is accompanied by a tetragonal distortion and the appearance of a gap in the magnetic excitation spectrum. The low-temperature noncollinear magnetic structure has been definitively resolved. Taken together, the crystal and magnetic structures indicate a staggered ordering of the V d orbitals. The anisotropy gap is a consequence of unquenched V orbital angular momentum.

cond-mat.str-el↗

arXiv2002

Coordinated, Interactive Data Visualization for Neutron Scattering Data

The overall design of the Integrated Spectral Analysis Workbench (ISAW), being developed at Argonne, provides for an extensible, highly interactive, collaborating set of viewers for neutron scattering data. Large arbitrary collections of spectra from multiple detectors can be viewed as an image, a scrolled list of individual graphs, or using a 3D representation of the instrument showing the detector positions. Data from an area detector can be displayed using a contour or intensity map as well as an interactive table. Selected spectra can be displayed in tables or on a conventional graph. A unique characteristic of these viewers is their interactivity and coordination. The position "pointed at" by the user in one viewer is sent to other viewers of the same DataSet so they can track the position and display relevant information. Specialized viewers for single crystal neutron diffractometers are being developed. A "proof-of-concept" viewer that directly displays the 3D reciprocal lattice from a complete series of runs on a single crystal diffractometer has been implemented.

physics.data-an↗

arXiv2002

Analyzing Single Crystal Time-of-Flight Neutron Data

Software for time-of-flight single crystal diffractometer (SCD) data visualization and analysis was originally written to be run in batch mode on VMS-VAX systems. Modern computers and software tools allow a new level of visualization and user interaction. The Integrated Spectral Analysis Workbench (ISAW) is being extended and customized for SCD measurements. To this end, new viewers and operators have been added to ISAW. One of the new operators allows running a program written in another language, such as C or FORTRAN, to integrate tested software into the object-oriented package. This provides a method for preserving earlier software development while making use of modern tools.

cond-mat.mtrl-sci↗