Structural, magnetic and transport properties of double perovskite compounds (Sr 2−3xLa 2xBa x)FeMoO 6

Abstract

The crystal structure and magnetic properties of a series of ordered double perovskite oxides (Sr 2−3 x La 2 x Ba x )FeMoO 6 ( 0 ⩽ x ⩽ 0.3 ) have been investigated. X-ray powder diffraction reveals that the crystal structure of the compounds changes from a tetragonal I4/m lattice to a cubic Fm 3 ¯ m lattice around x = 0.2 . Though the nominal average size of the A site cation of (Sr 2−3 x La 2 x Ba x )FeMoO 6 is designed to be almost independent of x, the refinements of the crystal structure show that the lattice constants increase with x in both the tetragonal and the cubic phase regions due to electron doping. As the x increases, the degree of cationic ordering on the B site is decreased pronouncedly, while the Curie temperature of the compounds is nearly unchanged. The saturation magnetization of the compounds decreases with x and shows a linear dependence on the degree of cation ordering. The resistivity of the parent compound shows a semiconducting behavior below room temperature, but those of the doped samples exhibit a metal–semiconductor transition. A correlation between the resistivity and metal-semiconducting transition temperature ( T M−S) is observed. The resistivity and T M−S of the compounds decrease with x for x ⩽ 0.2 and increase for x ⩾ 0.2 . Magnetoresistance of the compounds is reduced by the La/Ba doping. All these observations can be understood based on the interplay of the electron doping, change in bandwidth and the anti-site defect concentration.