Rare earth-doped bismuth ferrite via LFZ: Improved dielectric and magnetic properties

Bismuth ferrites are recognized as a promising multiferroic material for various applications. However, some challenges still need to be addressed. In this work, the enhancement of the dielectric and magnetic properties resulting from rare-earth substitution at the Bi-site of BiFeO 3 is presented. Bi 0 . 9 RE 0 . 1 FeO 3 (RE = La, Nd, Sm, Eu, Dy, Er) fibers were grown using the Laser Floating Zone technique. Structural characterization revealed the polyphasic nature of the samples, showing that the substitution of Bi 3+ by RE 3+ ions occurred only in the case of europium doping, forming the Bi 0 . 8 Eu 0 . 2 FeO 3 phase. Dielectric characterization demonstrated frequency-dependent behavior with single relaxation processes (except for Er-doped fibres, which exhibited two). Compared with pristine BiFeO 3 (comparison at 1 kHz, 300 K), all doped samples presented significantly reduced dielectric losses, leading to lower loss tangent values (< 1), while the Eu-doped fibre combined the highest dielectric constant with the lowest dielectric losses, thus showing the most promising dielectric performance. The calculated activation energies of the relaxation mechanisms were considerably higher than those of undoped BiFeO 3 , confirming the impact of rare-earth incorporation. Magnetic characterization of the Eu-doped fiber revealed weak ferromagnetic behavior, deviating from the typical antiferromagnetic characteristic of BiFeO 3 . Hysteresis loop measurements showed a coercivity of 10 kOe at 300 K, suggesting that the magnetic properties are strongly influenced by europium doping.