(X=Mn,Ni,Cu,Zn) double perovskites*

Oxide double perovskites have been extensively studied for a wide range of applications ranging from spintronics  to semiconducting devices. In d-group oxide double perovskites the correlated nature of electrons may give rise to metal to insulator transitions which may exhibit exotic properties like Giant and Colossal magnetoresistance (CMR and GMR). In this study, we explore the structural, electronic and magnetic properties of the double perovskites Ba₂Fe_{1- p}X_pMoO₆ (X=Mn,Ni,Cu,Zn). A systematic investigation is performed within the GGA+U approximation of Density Functional Theory (DFT), which shows the compositionally controlled metal to insulator transition with alloying in Fe-Mn and and Fe-Zn double perovskites. More precisely, a Mott transition is observed in the case of Fe-Mn alloys, while for the Fe-Zn system a complete insulating behaviour is observed above 50% Zn substitution. On the other hand, for the Fe-Cu and Fe-Ni systems, a half-metallic behavior is observed throughout the compositional space. We analyse the magnetic ordering of these phases in details. Ba₂Fe_0.5Mn_0.5MoO₆ is predicted to be a ferromagnetic insulator in our study suggesting its use in spintronic applications.