Unexpected origin of magnetism in monoclinic Nb12O29 from first-principles calculations

Fang, C.M.; Van Huis, M.A.; Xu, Q.; Cava, R.J.; Zandbergen, H.W.

doi:doi:10.1039/C4TC02222J

Unexpected origin of magnetism in monoclinic Nb12O29 from first-principles calculations

Title

Unexpected origin of magnetism in monoclinic Nb12O29 from first-principles calculations

Author

Fang, C.M.
Van Huis, M.A.
Xu, Q.
Cava, R.J.
Zandbergen, H.W.

Faculty

Applied Sciences

Department

Quantum Nanoscience

Date

2014-11-12

Abstract

Nb12O29 is a 4d transition metal oxide that occurs in two forms with different symmetries, monoclinic (m) and orthorhombic (o). The monoclinic form has unusual magnetic properties; below a temperature of 12 K, it exhibits both metallic conductivity and antiferromagnetic ordering. Here, first-principles density-functional theory calculations are used to study the structure, relative stability and electronic properties of Nb12O29. The optimized crystal structures are in good agreement with experimental observations and total energy calculations show similar stability of the two phases, while a magnetic electronic state is slightly favoured for m-Nb12O29. The unusual magnetism of the monoclinic phase originates from a Stoner instability that can be attributed to the Nb atoms with valence states close to Nb5+, i.e., the atoms with an electronic configuration of [similar]d0. This is in clear contradiction to current models in which the magnetism is attributed to the presence of localized Nb4+ ions with a formal d1 configuration. Our study demonstrates that in complex structures, magnetic properties are best not inferred from ionic models, but require a full quantum mechanical calculation over the whole unit cell.

Subject

Gold for Gold
Open Access

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http://resolver.tudelft.nl/uuid:fd5b2697-f365-45ea-b37c-424f7f894011

DOI

https://doi.org/10.1039/C4TC02222J

Publisher

RSC Publishing

ISBN

2050-7534

Source

J. Mater. Chem. C, 2015, Advance Article