Abstract :
The substitutions at the Mn-site of the Pr0.5Ca0.5MnO3 manganite by various cations, without d orbitals or with d0 or d10 electronic configurations, have been studied by ac magnetic susceptibility and field-dependent magnetization. Low levels of substitution (1–5%) are found to be sufficient to hinder long-range ordering of the orbitals, charges and spins (CE-type antiferromagnetism). Consequently, ferromagnetic interactions competing with the antiferromagnetic ones are created. However, in the absence of participation of the substituted cations to the formation of an eg conduction band, the induced ferromagnetic fractions remain very small (1–3%). Interestingly, for all the investigated cations, the field-dependent magnetization curves, collected at 5 K with a maximum magnetic field of 5 T, exhibit abrupt steps. The largest jumps are obtained for Ga3+, Sn4+ (d10) and Fe3+ (d5 high-spin). The steep steps correspond to abrupt transformations of antiferromagnetic regions into ferromagnetic ones, the ferromagnetic fraction increasing from 1 to 3% up to ∼50% in one step.
