Crystal structures and magnetic properties of fluorite-related oxides Ln{sub 3}NbO{sub 7} (Ln=lanthanides)

Journal Article · Wed Apr 15 04:00:00 EDT 2009 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2008.12.012· OSTI ID:21370329

Doi, Yoshihiro ^[1]; Harada, Yuka; Hinatsu, Yukio ^[1]

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1. Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan)

Crystal structures and magnetic properties of the ternary oxides Ln{sub 3}NbO{sub 7} (Ln=La, Pr, Nd, Sm-Lu) are reported. Their powder X-ray diffraction measurements and Rietveld analyzes show that they have the fluorite-related structures with space group Pnma (Ln=La, Pr, Nd), C222{sub 1} (Ln=Sm-Tb), or Fm-3m (Ln=Dy-Lu). Magnetic susceptibility measurements were carried out from 1.8 to 400 K. The Ln{sub 3}NbO{sub 7} compounds for Ln=Pr, Gd, Dy-Yb show Curie-Weiss paramagnetic behavior, and Sm{sub 3}NbO{sub 7} and Eu{sub 3}NbO{sub 7} show van Vleck paramagnetism. On the other hand, two magnetic anomalies were observed for both Nd{sub 3}NbO{sub 7} (0.6 and 2.7 K) and Tb{sub 3}NbO{sub 7} (2.0 and 3.2 K). From the results of specific heat measurements, it was found that these anomalies are due to the antiferromagnetic ordering of Ln ions in two different crystallographic sites (the 8-coordinated and 7-coordinated sites). - Ternary oxides Ln{sub 3}NbO{sub 7} (Ln=lanthanides) have the fluorite-related structures with space group Pnma (Ln=La, Pr, Nd), C222{sub 1} (Ln=Sm-Tb), or Fm-3m (Ln=Dy-Lu). In them, Nd{sub 3}NbO{sub 7} and Tb{sub 3}NbO{sub 7} show 'two-step' antiferromagnetic transitions due to the long-range antiferromagnetic ordering of Ln ions in different crystallographic sites.

• OSTI ID: 21370329
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 4 Vol. 182; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANTIFERROMAGNETISM
CHALCOGENIDES
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALLOGRAPHY
DIFFRACTION
FLUORITE
HALIDE MINERALS
MAGNETIC PROPERTIES
MAGNETIC SUSCEPTIBILITY
MAGNETISM
MINERALS
NIOBIUM COMPOUNDS
ORTHORHOMBIC LATTICES
OXIDES
OXYGEN COMPOUNDS
PARAMAGNETISM
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
REFRACTORY METAL COMPOUNDS
SCATTERING
SPACE GROUPS
SPECIFIC HEAT
SYMMETRY GROUPS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION