Effects of La-doping on the ferrimagnetism in double perovskite Y2MnCrO6

The La3+ doped Y2-2yLa2yMnCrO6 (y = 0-0.4, 0.9) polycrystalline samples have been synthesized by means of a standard solid-state reaction method. For lightly doped samples with y ≤ 0.3, the refined structural parameters of XRD patterns display a decrease tendency of structural anisotropy with increasing La content, suggesting a gradual reduction of the octahedral tilting in the compounds with increasing A-site cation size. The temperature dependence of magnetization gives that the ferrimagnetic state at temperatures below ∼75 K for the prototype Y2MnCrO6 remains till y = 0.3, while the samples with y = 0.4 and 0.9 show a much higher transition temperature at ∼120 K. However, for the ferrimagnetic samples with y ≤ 0.2, a detailed analysis on the high-temperature paramagnetic susceptibility reveals that the antiferromagnetic coupling within the Cr3+ sublattice is obviously enhanced with increasing La3+ content, which is an unfavorable factor for the ferrimagnetism. The electrical transport properties of the samples are dominated by the thermal activation mechanism, and the activation energy decreases distinctly with increasing y (y ≤ 0.3). The results indicate that the ferrimagnetism in Y2MnCrO6 oxide is suppressed with increasing A-site average cation size.