Structural, transport, magnetic properties and Raman spectroscopy of orthorhombic Y_1-xCa_xMnO₃ (0≤x≤0.5)

Orthorhombic Y_1-xCa_xMnO₃ (0≤x≤0.5) was prepared, and the variations with x of its structural, magnetic, and electrical properties and the polarized Raman spectra were investigated. The lattice parameters change systematically with x. Although there are strong indications for increasing disorder above x = 0.20, the average structure remains orthorhombic in the whole substitutional range. Ca doping increases the conductivity, but the temperature dependence of resistivity ρ(T) remains semiconducting for all x. The average magnetic exchange interaction changes from antiferromagnetic for x<0.08 to ferromagnetic for x>0.08. The evolution with x of the Raman spectra provides evidence for an increasingly disordered oxygen sublattice at x≥0.10, presumably due to quasistatic and/or dynamical Jahn-Teller distortions.