Electronic structures of non-half-metallic antiferromagnetic double perovskites ALaVMoO$_6$ (A = Ca, Sr, and Ba)

Recently, double perovskites $A$LaVMoO$_6$ ($A=$ Ca and Sr) of the $Fm\bar{3}m$ space group were proposed experimentally to be half-metallic antiferromagnets.\footnote{Uehara, Yamada, and Kimishima, Solid St. Commun. \textbf{129}, 385 (2004).} The electronic structures and magnetism of the double perovskites $A$LaVMoO$_6$ ($A=$ Ca, Sr, and Ba) were determined within the generalized gradient approximation to density functional theory using the all-electron full-potential linearized augmented plane wave (FLAPW) method.\footnote{Wimmer, Krakauer, Weinert, and Freeman, PRB \textbf{24}, 864 (1981).} The $A=$ Ca case shows \emph{metallic} ferrimagnetism as the most stable phase, with magnetic moments of $1.15\;\mu_B$ for V and $-0.53\;\mu_B$ for Mo, whereas the Sr and Ba cases are calculated to be almost non-magnetic metals. Comparing the calculated density of states, we find that the heavier $A$ implies stronger hybridization between the divalent atom $sp$ states and the transition metal atom $d$ states. The stronger $sp$-$d$ hybridization is considered to be responsible for the suppression of magnetism for the Sr and Ba cases. These results, at least for the $Fm\bar{3}m$ space group, are in contrast with the recent experimental result proposing half-metallic antiferromagnetism for $A=$ Ca and Sr.