Core and surface structure and magnetic properties of mechano-synthesized LaFeO3 nanoparticles and their Eu3+-doped and Eu3+/Cr3+-co-doped variants

Abstract The core and surface structure and magnetic properties of mechano synthesized LaFeO 3 nanoparticles (30–40 nm), their Eu 3+ -doped (La 0.70 Eu 0.30 FeO 3 ), and Eu 3+ /Cr 3+ co-doped (La 0.70 Eu 0.30 Fe 0.95 Cr 0.05 O 3 ) variants are reported. Doping results in a transition from the O ′ -type to the O-type distorted structure. Traces of reactants, intermediate phases, and a small amount of Eu 2+ ions were detected on the surfaces of the nanoparticles. The nanoparticles consist of antiferromagnetic cores flanked by ferromagnetic shells. The Eu 3+ dopant ions enhance the magnetization values relative to those of the pristine nanoparticles and result in magnetic susceptibilities compatible with the presence of Eu 3+ van Vleck paramagnetism of spin–orbit coupling constant (λ = 363 cm −1 ) and a low temperature Curie–Weiss like behavior associated with the minority Eu 2+ ions. Anomalous temperature-dependent magnetic hardening due to competing magnetic anisotropy and magnetoelectric coupling effects together with a temperature-dependent dopant-sensitive exchange bias, caused by thermally activated spin reversals at the core of the nanoparticles, were observed.