Site-Selective Doping Effect in AMn₃V₄O₁₂ (A = Na⁺, Ca²⁺, and La³⁺)

Abstract

A-site-ordered perovskite-structure oxides with Mn and V at A' and B sites, respectively, were synthesized by using a high-pressure method. Valence-state analyses revealed that the A-site substitution modulated the valence states of the Mn ions at the A' site and V ions at the B site sequentially. By changing the A-site ions from Na(+) to Ca(2+) and from Ca(2+) to La(3+), the valence distribution changed site-selectively from Na(+)Mn(2.33+)3V(4+)4O12 to Ca(2+)Mn(2+)3V(4+)4O12 and to La(3+)Mn(2+)3V(3.75+)4O12. The electrons of the A'-site Mn were localized and contributed to the magnetic properties, that is, spin-glass-like behavior in NaMn3V4O12 and antiferromagnetic behavior in CaMn3V4O12 and LaMn3V4O12. The valence electrons of the B-site V, in contrast, were delocalized, as could be seen from the low resistivity of the samples. The delocalized electrons at the B-site V did not correlate with the localized spins at the A'-site Mn.