Chiranjib Nayek

Role of oxygen vacancy and Fe–O–Fe bond angle in compositional, magnetic, and dielectric relaxation on Eu-substituted BiFeO3 nanoparticles

The influence of oxygen vacancies on the dielectric relaxation behavior of pure and Eu-substituted BiFeO3 nanoparticles synthesized by a sol-gel technique has been studied using impedance spectroscopy in the temperature range of 90 °C to 180 °C. The electric relaxation time and activation energy of the oxygen vacancies can be calculated from the Arrhenius equation, and found to be 1.26 eV and 1.76 eV for pure and Eu-substituted BiFeO3, respectively. Substitution induces structural disorder and changes in the Fe-O-Fe bond angle, leading to alteration of the magnetic properties, observed from magnetic studies and evaluated using Rietveld refinement of the XRD patterns. X-ray photoelectron spectroscopy (XPS) confirms the shifting of the binding energy of the Bi 4f orbital, establishing Eu substitution at the Bi site. Calculation of the area under the Fe(2+)/Fe(3+) (2p) and O (1s) XPS spectra gives approximate values of the oxygen vacancies.

Origin of enhanced magnetization in rare earth doped multiferroic bismuth ferrite

We report structural and magnetic properties of rare earth doped Bi0.95R0.05 FeO3 (R = Y, Ho, and Er) submicron particles. Rare earth doping enhances the magnetization and the magnetization shows an increasing trend with decreasing dopant ionic radii. In contrast to the x-ray diffraction pattern, we have seen a strong evidence for the presence of rare earth iron garnets R3Fe5O12 in magnetization measured as a function of temperature, in selected area electron diffraction, and in Raman measurements. Our results emphasised the role of secondary phases in the magnetic property of rare earth doped BiFeO3 compounds along with the structural distortion favoring spin canting by increase in Dzyaloshinskii-Moriya exchange energy.

Magnetic, dielectric and magnetodielectric properties of PVDF-La0.7Sr0.3MnO3 polymer nanocomposite film

We have investigated the structure, magnetic and dielectric properties of PVDF-La0.7Sr0.3MnO3 polymer nanocomposite thick film fabricated by dip coating technique along with the magnetodielectric effect. The structure and dielectric properties show the enhanced β phase in the composite compared to the PVDF film. The coupling between the ferroelectric and magnetic phases in the composite is revealed in the form of dielectric anomaly at the ferromagnetic Curie temperature. We observed 1.9% magnetodielectric effect at 300 K with the possibility of enhanced effect near the transition temperature. In addition, the analysis of the electric modulus indicates that the composite exhibits interfacial related relaxation and it follows Arrhenius Law. Our study suggests that the ac conductivity of the PVDF-La0.7Sr0.3MnO3 composite could be explained by correlated barrier hopping mechanism.

Effect of europium substitution on the magnetic and optical properties of nanostructured bismuth ferrite

Single phase Bi(1−x)EuxFeO3 multiferroic nanoparticles were synthesized by tartaric acid assisted sol-gel method and the effect of Eu substitution in Bismuth ferrite (BFO) was investigated on the structural, optical and magnetic properties. It was observed a gradual structural transition from rhombohedral R3c to orthorhombic Pbnm with the increase of Eu content resulted from the lattice distortion in BFO system due to the smaller radius of Eu3+ ions. The optical band gap of BFO was altered with respect to the change of particle sizes with the increment of Eu content. The magnetic property of Bi(1−x)EuxFeO3 system was found to be increased with the increase of Eu substitution. This might be attributed to the substitution-induced suppression of spiral spin modulation caused by an appropriate substitution of Eu in the BFO system.