Structural, Microstructural, and Magnetic Properties of Ce and Sr-co-Substituted (La_2-x Vac _x )NiTiO₆ (x = 0, 0.1)...

The synthesis of materials in the La_2-x (CeSr) _m Sr _n □ _p NiTiO_6‑δ series (where □ denotes vacancies, with m, n, and p ranging from 0 to 0.2, and x = 2m + n + p taking values of 0.4 and 0.6) was attempted using a modified Pechini method. A comprehensive chemical, structural, and microstructural characterization was carried out using X-ray diffraction (conventional and synchrotron), neutron powder diffraction, selected area electron diffraction, high-resolution transmission electron microscopy, and X-ray absorption spectroscopy. The results highlight that single-phase samples are obtained for compositions with low cerium and low vacancy contents (m ≤ 0.1 and p ≤ 0.1). The structural study reveals that the compounds present monoclinic symmetry, space groups P2 ₁ /n or P2 ₁ , with Ni and Ti cations exhibiting different degrees of disorder or short-range order, influenced by the existence of A-site vacancies and the contents of Ce⁴⁺ and Sr²⁺ ions. The magnetic behavior is closely related to the cationic disorder at the B-site. The presence of antisite defects and short-range Ni-O-Ni interactions contribute to a lack of three-dimensional antiferromagnetic ordering, probably forming instead of random Ni²⁺ antiferromagnetic clusters at low temperatures.