A-site ion-size effect on the transport and magnetic properties of Ce doping Pr0.3Ce0.2CaxSr0.5−xMnO3 (0≤x≤0.25)

Abstract

The effects of A-site ion-size 〈rA〉 on the crystal structures, transport and magnetic properties of the perovskite manganese oxide Pr0.3Ce0.2CaxSr0.5-xMnO (0 ≤ x ≤ 0.25) have been investigated. In those compounds, when 0≤x≤0.125, the temperatures (Tmax) of the resistivity maximums below Curie Temperature TC are correlated with the Kondo-like scattering of Ce3+ and the onset of antiferromagnetic ordering of Ce3+ with respect to the Mn-sublattice moments. The decrease of 〈rA〉 causes the anomalous increase of lattice parameters b, c and unit cell volume, the decrease of the differences of TC and Tmax, the weakening of the Kondo-like scattering and magnetic order of Ce3+, and the enhancement of saturation magnetic moment, which give the evidences of the valence enhancing of Ce ions from + 3 toward + 4 with 〈rA〉 decreasing. Although the Ca doping is expected to drive the system toward the antiferromagnetic ground state, the increase of valence of Ce enhances the content of Mn3+ in the system, which drives the system to the ferromagnetic ground state. The changes of ion-size 〈rA〉 and the valence of Ce are co-operating on the transport and magnetic properties of the half-doped manganites.