Mechanosynthesized LaFeO 3 Nanoparticles and Their Eu 3 -Doped and Eu 3 /Cr 3 -Co-Doped Modifications: Structural and Magnetic Studies
47 Pages Posted: 12 Dec 2023
Abstract
The structure and magnetic properties of mechanosynthesized LaFeO3 nanoparticles (30-40 nm) and their Eu3+-doped (La0.70Eu0.30FeO3) and Eu3+/Cr3+ co-doped (La0.70Eu0.30Fe0.95Cr0.05O3) modifications are reported. Doping has resulted in a transition from the O՝-type to the O-type distorted structure. All nanoparticles exhibit complex surface structures with traces of both reactants and intermediate phases. Tiny amounts of Eu2+-ions are detected on the surfaces of doped nanoparticles. 57Fe Mӧssbauer and magnetic measurements show the nanoparticles to consist of antiferromagnetic cores flanked by ferromagnetic-like shells. The partial ionic substitution of La3+ by Eu3+ has led to higher ZFC and FC magnetization values for the doped nanoparticles relative to those of the pristine. The best fits of the Eu-related molar susceptibilities for both materials are attained by assuming an Eu3+ van-Vleck paramagnetism with a spin–orbit coupling constant of 363 cm-1 coexisting with a low temperature Curie-Weiss like behaviour of the weakly-coupled antiferromagnetic sublattice of the minority Eu2 ions. The anomalous temperature-dependent magnetic hardening observed in all materials is linked to competing magnetic anisotropy and magnetoelectric coupling effects. All nanoparticles exhibit a temperature-dependent dopant-sensitive exchange bias that is attributed to a thermally activated spin reversal at the nanoparticles’ cores
Keywords: Orthoferrites, Mechano-synthesis, XRD, Mössbauer spectroscopy, van-Vleck paramagnetism
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