The Structure and Magnetic Properties of Pr3MO7 with M = Nb, Ta, and Sb

✍ Scribed by J.F. Vente; R.B. Helmholdt; D.J.W. IJdo

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 271 KB
• Volume: 108
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1994.1003

✦ Synopsis

The crystal structure of the fluorite-related praseodymium compounds with the composition (\operatorname{Pr}{3} \mathrm{OO}{7}, M=\mathrm{Nb}), Ta, and (\mathrm{Sb}), have been determined using Rietveld refincment from (X)-ray and ncutron powder diffraction data at 293 and (4 \mathrm{~K}). The structure described is orthorhombic with space group (\mathrm{Cmcm}) ( (\mathrm{No}). 63). It is a superstructure of the cubic fluorite structure with unit cell parameters (a_{\text {orth }} \approx 2 a_{\mathrm{c}}, b_{\text {orth }} \approx c_{\text {orth }} \approx a_{\mathrm{c}} \sqrt{2}), as in (\mathrm{La}{3} \mathrm{NbO}{7}). This structure consists of chains of corner linked (\mathrm{MO}{6}) octahedra parallel with the (c)-axis. The magnetic susceptibility was measured between 4 and (300 \mathrm{~K}). The compounds obey the Curie-Weiss law including a Van Vleck temperature independent term. (\mathrm{Pr}{3} \mathrm{SbO}_{7}) shows a small deviation from this law below (25 \mathrm{~K}). O 1994 Acadcmic Press, inc.