Structural, dielectric, and magnetic properties of multiferroic Bi1-xRExFeO3 (x=0.05, 0.15, 0.2 and RE=Nd3+, Eu3+) powders grown by sol-gel method

Rare-earth substituted multiferroic Bi1-xRExFeO3 powders with chemical compositions (x = 0.05, 0.15, 0.20 and RE = Nd3+; Eu3+) are synthesized by sol-gel method. The powder X-ray diffraction results manifest that samples are in single phase (R3c) for x < 0.15; the structural phase transformation from the distorted perovskite R3c to the ideal perovskite (Pm3 m) was made for BFO-Nd at x = 0.15 and for BFO-Eu (BEFO) at x = 0.20. Theoretical analyses allowed us to propose & UGamma;4 (k = 0, 0, 0) as the irreducible representation associated to the distortion of the ideal perovskite Pm3 m to the R3c distorted one, where the displacement of Fe atom along [0 0 1] axis is considered as so the parameter order & eta; = (0; 0; & eta;3), which drives the transition Pm3 m -R3c. Dielectric properties of Bi1-xRExFeO3 change noticeably with concentration and nature of RE-doping. The increase of Nd and Eu concentration decreases clearly the dielectric temperature anomalies corresponding to the ferroelectricparaelectric phase transitions, which are more shifting towards lower temperature when the dopant is Eu. Magnetic measurements indicate that antiferromagnetic BFO-Nd (BNFO) powders became ferromagnetic at (0.15 & LE;x & LE; 0.2), while the BFO-Eu (BEFO, x & LE; 0.15) compounds, antiferromagnetic with a small remanant magnetization, become weak ferromagnetic when x = 0.20.