Rietveld refinement of magnetic structures from pulsed-neutron-source powder-diffraction data

Conference · Fri Jan 01 00:00:00 EST 1993

DOI:https://doi.org/10.1016/0921-4526(95)92830-4· OSTI ID:6520029

Robinson, R A; Lawson, A C; Larson, A C; Von Dreele, R B; Goldstone, J A

The General Structure Analysis System, GSAS, has recently been modified to include magnetic neutron-scattering cross-sections. Low-temperature diffraction data have been taken on the hexagonal noncollinear antiferromagnet UPdSn on both the HIPD and the NPD powder diffractometers at LANSCE. The low-resolution data reveal that the magnetic structure has orthorhombic symmetry (magnetic space group P[sub c]112[sub 1]) between 25K and 40K, and monoclinic symmetry (magnetic space group P[sub c]l12[sub 1]) below 25K. The high-resolution data reveal that there are structural distortions with corresponding symmetry changes in each of these phases, to give chemical space groups Cmc2[sub 1] and P2[sub 1] respectively, while the paramagnetic phase above 40K has space group P6[sub 3]mc. Using GSAS, we have refined data sets from both diffractometers simultaneously, including both magnetic and structural cross-sections. Magnetoelastic coefficients for the distortions have been extracted and we have determined the sip of the coupling between the structural monoclinicity and the magnetic monoclinicity. The magnetic results from Rietveld refinement are in good agreement with model fitting to the integrated intensities of seven independent magnetic reflections and these, in turn, agree with measurements made on the same sample using the constant-wavelength reactor technique. Our results therefore validate, to some level, both the technique of using spallation sources for complicated magnetic structures and the specifics of the GSAS Rietveld code.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 6520029
• Report Number(s): LA-UR-93-1519; CONF-9305177-2; ON: DE93012740
• Resource Relation: Journal Volume: 213-214; Conference: 12. International collaboration of advanced neutron sources meeting (ICANS), Abingdon (United Kingdom), 24-28 May 1993
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
NEUTRON SOURCES
NEUTRON DIFFRACTION
NEUTRON SPECTRA
MAGNETIC PROPERTIES
CROSS SECTIONS
MAGNETIC FIELDS
NEUTRON DIFFRACTOMETERS
PALLADIUM COMPOUNDS
TIN COMPOUNDS
URANIUM COMPOUNDS
ACTINIDE COMPOUNDS
COHERENT SCATTERING
DIFFRACTION
DIFFRACTOMETERS
MEASURING INSTRUMENTS
PARTICLE SOURCES
PHYSICAL PROPERTIES
RADIATION SOURCES
SCATTERING
SPECTRA
TRANSITION ELEMENT COMPOUNDS
665100* - Nuclear Techniques in Condensed Matter Physics - (1992-)