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Structure and Magnetism in CrTa2O6: A Trirutile Oxide Based on Cr2+

✍ Scribed by M. Saes; N.P. Raju; J.E. Greedan


Publisher
Elsevier Science
Year
1998
Tongue
English
Weight
321 KB
Volume
140
Category
Article
ISSN
0022-4596

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✦ Synopsis


CrTa2O6, a rare example of an oxide containing Cr 2Ψ‰ , was prepared by solid state reaction from a mixture of Cr2O3, Ta2O5, and Ta in a sealed silica tube at 1050Β°C. It exhibits a slightly distorted trirutile structure described in P21/n with a ‫؍‬ 4.738(1), b ‫؍‬ 4.7421(6), c ‫؍‬ 9.2972(9), and ‫؍‬ 90Β°55(1) as determined from Guinier-Hagg data and CuK 1 radiation, in excellent agreement with previous reports. The crystal structure was refined from powder neutron diffraction data at 20 K. The Cr 2Ψ‰ environment is distorted from that usually found in trirutile oxides with Cr-O distances ranging from 2.06(1) to 2.270(9) A s consistent with a static Jahn-Teller distortion as expected for high-spin Cr 2Ψ‰ . Magnetic susceptibility data show a Curie-Weiss behavior with C ‫؍‬ 2.79(1) emu mol ؊1 K ؊1 , which compares well with the expected value of 3.0 emu mol ؊1 K ؊1 for the high-spin state. A ‫؍‬ ؊30.0(8) K indicates the dominance of antiferromagnetic exchange. A susceptibility maximum at 11 K is evidence for long-range antiferromagnetic order. Low-temperature neutron diffraction data confirm a TN ‫؍‬ 10.3(1) K and a complex magnetic structure with ordering wave vector kK ‫؍‬ (1/4 1/4 1/4) as seen for some other trirutile oxides. For T > TN, two-dimensional, short-range correlations are seen in the form of a Warren line shape. Interestingly, the two-dimensional correlations persist into the ordered regime, at least to 9.0 K. The properties of CrTa2O6 are compared with other known trirutile MTa2O6 and MSb2O6 materials.


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Results from crystal structural analyses of CuSb 2 O 6 with the trirutile structure, which transforms from the phase (space group P2 1 /n) to the -phase (space group P4 2 /nmn) at 380 K, are reported. While extensive twinning prevents the single crystal structure determination of the modification, t