Enhancement of magnetic and ferroelectric properties of BiFeO3 by Er and transition element (Mn, Co) co-doping

• BiFeO3, Bi0.8Er0.2FeO3, Bi0.8Er0.2Fe0.9Mn0.1O3 and Bi0.8Er0.2Fe0.9Co0.1O3 nanoparticles were prepared by sol–gel method.
• The introduction of Er and Mn, Co into BiFeO3 leads into a phase transition with reduced grain size.
• The phase transformation combined with size reduction has significantly increased saturated polarization (Ps), remanent polarization (Pr) and saturated magnetization (Ms), remanent magnetization (Mr) behaviors of the doped samples with the same variation trend.
• The formation of dipolar defect complexes (DDCs) in the doped samples may also contribute to the improved ferroelectric property.
• Bi0.8Er0.2Fe0.9Mn0.1O3 exhibits significantly improved ferroelectric and ferromagnetic properties.

BiFeO3(BFO), Bi0.8Er0.2FeO3 (BEFO), Bi0.8Er0.2Fe0.9Mn0.1O3 (BEFMO) and Bi0.8Er0.2Fe0.9Co0.1O3(BEFCO) nanoparticles were prepared by sol–gel method having an average size of 200 nm for BFO, under100 nm for BEFO and under 60 nm for BEFMO and BEFCO. Phase transition from a rhombohedral symmetry (R3c) for BFO to an orthorhombic symmetry (Ibmm) for BEFO, BEFMO and BEFCO has been observed. The phase transformation combined with size reduction has significantly improved both ferroelectric and ferromagnetic behaviors of the doped samples in a similar way. The formation of dipolar defect complexes (DDCs) in the doped samples also contributes to the improved ferroelectric property with saturated polarization (Ps) of 0.375 μC/cm2 and remanent polarization (Pr) of 0.244 μC/cm2 for BEFMO. Size effect may also impact the simultaneously developed Pr for BEFMO and BEFCO. Owning to the interactions between the ferromagnetic and antiferromagnetic microdomains, improved saturated magnetization (Ms) and remanent magnetization (Mr) are also observed in BEFMO.