Issue EPL Volume 80, Number 3, November 2007 Article Number 37008 Number of page(s) 5 Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties DOI 10.1209/0295-5075/80/37008 Published online 10 October 2007

EPL, 80 (2007) 37008
DOI: 10.1209/0295-5075/80/37008

Orbital-quenchinginduced magnetism in Ba₂NaOsO₆

K.-W. Lee and W. E. Pickett

Department of Physics, University of California - Davis, CA 95616, USA

received 15 August 2007; accepted in final form 11 September 2007; published November 2007
published online 10 October 2007

Abstract
The double perovskite Ba₂NaOsO₆ with heptavalent Os (d¹) is observed to remain in the ideal cubic structure (i.e. without orbital ordering) despite single occupation of the t_2g orbitals, even in the ferromagnetically ordered phase below 6.8 K. Analysis based on the ab initio dispersion expressed in terms of an Os t_2g-based Wannier function picture, spin-orbit coupling, Hund's coupling, and strong Coulomb repulsion shows that the magnetic OsO₆ cluster is near a momentless condition due to spin and orbital compensation. Quenching (hybridization) then drives the emergence of the small moment. This compensation, unprecedented in transition metals, arises in a unified picture that accounts for the observed Mott insulating behavior.

PACS
71.70.Ej - Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect.
71.27.+a - Strongly correlated electron systems; heavy fermions.
77.84.Bw - Elements, oxides, nitrides, borides, carbides, chalcogenides, etc..

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