Insulator--Metal Transition due to La Doping in Double Perovskite Sr₂MnMoO₆

Resistivity, thermal diffusivity, lattice and magnetic properties of double perovskite Sr_2-xLa_xMnMoO₆ are investigated with systematic change of La doping concentration x from 0.0 to 0.4. The insulator to metal phase transition is observed with increasing x above 0.3, suggesting that the extra electrons via substitution of La³⁺ for Sr²⁺ ions occupy mainly the conduction Mo-4d band. According to the insulator to metal phase transition, the thermal diffusivity of Sr_2-xLa_xMnMoO₆ enhances from 0.33 cm²/s at x = 0.0 to 0.49 cm²/s at x = 0.4. We further investigate the La doping effects on the lattice and magnetic properties.