Large room-temperature intergrain magnetoresistance in double perovskite SrFe1−x(Mo or Re)xO3

We report significant intergrain magnetoresistance (IMR) in polycrystalline double perovskites of ${\mathrm{SrFe}}_{\text{1−x}}(\mathrm{Mo or Re}{)}_x{\mathrm{O}}_{\mathrm{3}}$ at room temperature. Systematics of the temperature dependence of IMR indicates that the observed large room-temperature IMR in ${\mathrm{SrFe}}_{\mathrm{1/2}}{\mathrm{Mo}}_{\mathrm{1/2}}{\mathrm{O}}_{\mathrm{3}}$ originates from the ferrimagnetic nature of insulating grain boundaries as well as the half-metallicity of this perovskite. Our results indicate that a new avenue for spin-polarized tunneling junctions is to utilize insulating interface layers with ferromagnetic or ferrimagnetic coupling.