Ferromagnetic superexchange in insulating C r2Mo O6 by controlling orbital hybridization

We report the magnetic and electronic structures of the inverse-trirutile compound Cr₂MoO₆. Despite the same crystal symmetry and similar bond lengths and bond angles as Cr₂TeO₆, Cr₂MoO₆ possesses a magnetic structure different from that in Cr₂TeO₆. ab initio electronic structure calculations show that the sign and strength of the Cr-O-Cr superexchange coupling is strongly influenced by the hybridization between the filled O₂p and empty Mo₄d orbitals: the virtual transfer of an O₂p electron to the empty Mo4d orbitals leaves the O₂p partially occupied, which leads to ferromagnetic exchange between Cr moments. This result further substantiates our recently proposed mechanism for tuning the exchange interaction between two magnetic atoms by modifying the electronic states of nonmagnetic atoms in the exchange path through orbital hybridization. This approach is fundamentally different from the conventional methods of controlling the exchange interaction by either carrier injection or through structural distortions.