Orbital-quenching-induced magnetism in Ba2NaOsO6

The double perovskite Ba2NaOsO6 with heptavalent Os (d(1)) 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. Copyright (C) EPLA, 2007