Effect of the Mn3+ ion on electrical and magnetic properties of orthorhombic perovskite-type Ca(Mn1−xTix)O3−δ

Orthorhombic perovskite-type Ca(Mn1−xTix)O3−δ (0 ≤ x ≤ 0.7) was synthesized at 1173 K for 12 h in a flow of oxygen from a precursor gel prepared using citric acid and ethylene glycol. The Mn3+ ion was generated by substituting a Ti4+ ion in CaMnO3. The average particle size was 100–300 nm and did not depend on x. The lattice constants and the (Mn, Ti)–O distance increased linearly with increasing x. The variation in global instability index (GII) indicated that the instability of the structure increases monotonically with increasing x. Ca(Mn1−xTix)O3−δ was an n-type semiconductor that had its minimum values of electrical resistivity (ρ) and activation energy (Ea) at x = 0.1. Ca(Mn1−xTix)O3−δ (x = 0 and 0.1) exhibited a weak ferromagnetic behavior. The variation in μeff indicated that the spin state of the Mn3+ ion changes from low to high at x = 0.1, then reverts to low in the range of 0.2 ≤ x ≤ 0.7. The variations in ρ and Ea are explained by the number of electrons according to the change in the spin state of the Mn3+ ion.