Structural, magnetic and electrical properties of double-doped manganites Y0.5+ySr0.5−yMn1−yCryO3 (0≤y≤0.5)

We report an investigation on the evolution of structural, magnetic and transport properties in double-doped manganites Y0.5+ySr0.5−yMn1−yCryO3 (0≤y≤0.5), remaining eg electron density (x=0.5) unchanged. From a pseudo-cubic perovskite structure for Y0.5Sr0.5MnO3 with y=0, powder X-ray diffraction patterns demonstrate that Cr3+ substitution on the Mn-site leads to a tetragonal distortion, which increases with the doping level y. The temperature dependence of magnetic susceptibility shows that the magnetic state at low temperatures evolves from an antiferromagnetic-spin-glass state for y=0, undergoing a ferromagnetic-spin-glass state, finally to a ferrimagnetic state for y=0.5. The electrical transport properties of all samples show an insulator behavior dominated by the small polaron hopping mechanism and the activation energy increases significantly along with y. Consequently, the enhancement of ferromagnetic component in the Y0.5+ySr0.5−yMn1−yCryO3 series may be attributed to the anisotropic ferromagnetic superexchange interactions of Mn3+ ions collaborating with the ordered arrangement of Mn3+/Cr3+ ions, rather than the double exchange interaction via eg-electron hopping process.