Abstract
The influence of A-site size and disorder on metamagnetic transformation in polycrystalline Pr0.5−xLaxCa0.5MnO3 and Pr0.5Ca0.5−xBaxMnO3 at low temperature has been systematically investigated. The introduction of larger A-site cations such as La3+ or Ba2+ will locally suppress the lattice distortion. This “counterdistortion” effect becomes more pronounced with the increase in the A-site average ionic radius ⟨rA⟩, which is favorable to ferromagnetism. Thus the critical field HC1 corresponding to the first sharp metamagnetic step will decrease, and the field-induced magnetization M5 T will increase. However, the A-site ionic radii variance σ2 will dramatically increase when more barium is introduced and a spin glasslike state is induced, which is unfavorable to the stability of ferromagnetism state. Therefore, HC1 will increase and M5 T will decrease. Moreover, the evolution of resistivity at low temperature with σ2 exhibits strong correlation with that of magnetic properties.
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