Valence of Ti cations and its effect on magnetic properties of spinel ferrites TixM1-xFe2O4 (M = Co, Mn)

Powder samples of TixCo(1-x)Fe(2)O(4) (0.0 <= x <= 0.4) and TixMn(1-x)Fe(2)O(4) (0.0 <= x <= 0.3) were synthesized using a conventional method for preparing ceramics. X-ray diffraction analysis confirmed that the samples consisted of a single phase with a cubic (A)[B](2)O-4 spinel structure. The average molecular magnetic moment (mexp) measured at 10 K decreased monotonically with increasing x for two series of samples. According to previous investigations, Ti2+ and Ti3+ cations are present in these ferrites, but there are no Ti4+ cations; the magnetic moments of the Ti2+, Ti3+, and Mn3+ cations are assumed to couple antiferromagnetically with those of the Mn2+, Co2+, Co3+, Fe2+, and Fe3+ cations whenever they are at the (A) or [B] sublattice. The dependence of mexp of the two series of samples on the doping level x was fitted using a quantum-mechanical potential barrier, and the cation distributions in the two series of samples were obtained.