Structural Chemistry and Magnetic Properties of Nd₁₈Li₈Fe₅O₃₉ and Nd₁₈Li₈Co₄O₃₉: the Interplay of Cation and Spin Ordering

Abstract

Polycrystalline samples of Nd18Li8Fe5O39 and Nd18Li8Co4O39 have been synthesized using a solid-state method and studied by a combination of neutron diffraction, direct and alternating current magnetometry, and, in the case of Nd18Li8Fe5O39, Mössbauer spectroscopy. Both compounds adopt a cubic structure (space group Pm3-n, a0 ~ 11.9 Å) based on intersecting < 111 > chains made up of alternating octahedral and trigonal-prismatic coordination sites. The Fe4+ cations in Nd18Li 8Fe5O39 are found on only the smaller of the two distinct octahedral sites in the structure; Fe3+ and Li + are disordered over the larger octahedral site and the trigonal-prismatic site. The Nd3+ cations occupy sites between the chains. The smaller octahedral site is fully occupied by cobalt in Nd 18Li8Co4O39, with 25% of the larger octahedral sites being vacant; Li+ is only found on the prismatic sites. Nd18Li8Fe5O39 shows spin-glass-like behavior with a spin-freezing temperature of 5.75 K, whereas Nd18Li8Co4O39 appears to order antiferromagnetically at 2.3 K. In both cases, the magnetic coupling involves the Nd3+ sublattice.

Department(s)

Chemistry

International Standard Serial Number (ISSN)

0020-1669

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2008 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Dec 2008

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