Preparation, crystal structure, dielectric properties, and magnetic behavior of Ba₂Fe₂Ti₄O₁₃

The preparation, crystal structure, dielectric properties, and magnetic behavior of the new compound Ba₂Fe₂Ti₄O₁₃ are reported. Structural studies carried out by single-crystal X-ray diffraction and neutron powder diffraction show that this phase is isostructural with K₂Ti₆O₁₃ and Ba₂ZnTi₅O₁₃ (C2/m (No. 12); a = 15.216(1), b = 3.8979(3), c = 9.1350(6) Å, β = 98.460(7)°; V = 535.90(8) ų; Z = 2). The cations Fe³⁺ and Ti⁴⁺ are partially ordered among distorted octahedral sites with Ba²⁺ occupying eleven-coordinated polyhedra. Ba₂Fe₂Ti₄O₁₃ exhibits TE₀ resonance near 10 GHz with a dielectric constant of ∼28 and a dielectric loss tangent of 2 × 10^-3. The compound displays complex paramagnetic behavior with marked field dependence; the magnetization at 80 kA/m is several orders of magnitude smaller than that of most ferrites. Spin-glass effects have not been observed; however, weak collective interactions are clearly present. No magnetic ordering has been detected by neutron diffraction down to 13 K.