Interplay between spin-orbit coupling and strong correlation effects: Comparison of the three osmate double perovskites Ba sub(2)A OsO sub(6)(A=Na, Ca, Y)

• Published in: Physical review. B 2016-04, Vol.93 (15)
• Main Authors: Gangopadhyay, Shruba, Pickett, Warren E
• Format: Article
• Language: English
• Subjects: Charge density; Condensed matter; Correlation; Electronics; Exchange; Ferromagnetism; Perovskites; Spin-orbit interactions
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.93.155126

High formal valence Os-based double perovskites are a focus of current interest because they display strong interplay of large spin-orbit coupling and strong electronic correlation. Here we present the electronic and magnetic characteristics of a sequence of three cubic Os based double perovskites Ba sub(2)A OsO sub(6) (A=Na, Ca, Y), with formal valences of Os+ super(7)(d super(1)),Os super(+6)(d super(2)), and Os super(+5)(d super(3)). For these first principles based calculations we apply an "exact exchange for correlated electrons" functional, with exact exchange applied in a hybrid fashion solely to the Os (5d) states. While Ba sub(2) NaOsO sub(6) is a reported ferromagnetic Dirac-Mott insulator studied previously, the other two show antiferromagnetic ordering while all retain the undistorted cubic structure. For comparison purposes we have investigated only the ferromagnetic ordered phase. A metal-insulator transition is predicted to occur upon rotating the direction of magnetization in all three materials, reflecting the central role of spin-orbit coupling in these small gap osmates. Surprises arising from comparing formal charge states with the radial charge densities are discussed. Chemical shielding factors and orbital susceptibilities are provided for comparison with future nuclear magnetic resonance data.