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-delta (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-delta was an n-type semiconductor that had its minimum values of electrical resistivity (rho) and activation energy (E-a) at x = 0.1.Ca(Mn1-xTix)O3-delta(x = 0 and 0.1) exhibited a weak ferromagnetic behavior. The variation in mu(eff) 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 rho and E-a are explained by the number of electrons according to the change in the spin state of the Mn3+ ion. (C) 2006 Elsevier Ltd. All rights reserved.