Role of La substitution on structural, optical, and multiferroic properties of BiFeO3 nanoparticles

Abstract

The present work reports the influence of Lanthanum (La) substitution on the structural, optical, electrical, and magnetic properties of bismuth ferrite (BiFeO 3 ) nanoparticles (NPs). The compositions of Bi 1−x La x FeO 3 (0% < x < 20%) NPs, with 5% Bi-excess, were synthesized through sol-gel conventional route. The XRD results suggest the formation of rhombohedral perovskite structure (R3c space group) along with a minor secondary phase. The crystallite size calculated from XRD and FESEM was observed to decrease from 60.0 to 40.0 nm with an increase in La content. The bandgap calculated using UV-Vis spectroscopy was found to decrease with La doping, and PL spectroscopy infers formation of defects in La-BFO NPs. The P-E loop studies reveal that La-doped BFO exhibits ferroelectric behavior at room temperature. The various parameters such as spontaneous polarization, dielectric constant, and distribution parameter of relaxation time measured from the electrical investigation were found to increase up to 5% La doping BFO then start decreasing with further increase in the La content in BFO. The impedance spectra of La-BFO was fitted using the theory of Cole-Cole with R(C(R(QR)))(CR) model. It is observed that La-concentration above 5% generates excess space charge which might cross the threshold to start conduction resulting in degrading of multiferroic properties. The DC magnetization study revealed the ferromagnetic behavior of the samples at room temperature. It is observed that La substitution affects the shape of the magnetization hysteresis curve beyond 5% La-concentration, and transforming it to a neck-like formation providing evidence for the spin-canting effect in the samples. These results make La-doped BiFeO 3 NPs a propitious candidate for the multiferroic applications like highdensity data storage devices and supercapacitors.

Structural and spectroscopic analysis of HoMn2O5 multiferroics

“…A PL spectrum of HMO at room temperature is shown in figure 5. It can be seen that there are several broad emissions within 550-700 nm, which is within the visible emission range and above 700-900 nm corresponds to the near infrared emission [26]. Remarkably, two prominent emission peaks are observed in the spectrum, at about 701 nm (1.77 eV) which is attributed to the formal electronic transition from conduction to valence band or the presence of intrinsic defects in the oxygen sub-lattice and 880 nm (1.41 eV) which attributes to the lattice vibration of Mn-O stretching chemical bonds.…”

Role of Cr Doping on the Structure, Electronic Structure, and Electrochemical Properties of BiFeO3 Nanoparticles

“…The distorted rhombohedral crystal structure of BFO allows deformation in the central-local symmetry due to the spontaneous polarization caused by 6s 2 lone pairs of Bi 3+ ions which give rise to the ferroelectric properties of the material. On the other hand, the exchange interactions involving Fe 3+ ions result in the ferromagnetic ordering [22]. BFO demonstrates a ferromagnetic curie temperature of ~1102 K and an antiferromagnetic Néel temperature of ~644 K. There are many existing reports which show significant multiferroic properties in BFO [23].…”