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

Abstract

Powder samples of Ti_xCo_1−xFe₂O₄ (0.0 ≤ x ≤ 0.4) and Ti_xMn_1−xFe₂O₄ (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]₂O₄ spinel structure. The average molecular magnetic moment (μ_exp) 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 μ_exp 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.