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Crystalline Sm₂Ni₂O₅ (SNONPs) nanoparticles were synthesized via co-precipitation and sol–gel methods, while Ce₂Ni₂O₅ (CNONPs) and Ce₂Co₂O₅ (CCONPs) were prepared using a sol–gel route to investigate the effect of A-site (Sm, Ce) and B-site (Ni, Co) cation substitution on their structural, morphological, thermodynamic, and magnetic properties. XRD analysis confirmed that SNONPs crystallize in an orthorhombic Ima2 structure after annealing at 800°C, whereas CNONPs and CCONPs exhibit two-phase cubic structures (Fm-3m and Fd-3m). SEM revealed compact particles for co-precipitated SNONPs and fragmented morphologies for sol–gel samples. TEM showed spherical NPs with average sizes of ~33 nm (CNONPs) and ~63 nm (CCONPs). XPS analysis indicated mixed valence states, with stable Ce4+, predominant Ni2+, and high-spin Co3+. Thermodynamic and magnetic measurements (0–300 K) revealed distinct phase behavior. SNONPs exhibited spin freezing at 6 K, antiferromagnetic ordering at 9 K, and a ferromagnetic transition at 43.6 K. CNONPs showed no clear specific heat transition but displayed magnetic anomalies at 58 K, 139 K, and 216 K. In contrast, CCONPs showed a low-temperature antiferromagnetic ordering anomaly at 30 K and ferromagnetic ordering at 24 K. These results demonstrate that cation substitution, synthesis method, and particle size significantly influence magnetic interactions and phase transitions. The study highlights the tunability of brownmillerite oxides and identifies SNONPs as promising candidates for spintronic and low-temperature magnetic applications.
| Apply for student award at which level: | MSc |
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| Consent on use of personal information: Abstract Submission | Yes, I ACCEPT |