الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Multiferroic nanoparticles of Bi1–xBaxFeO3 (x = 0.10, 0.15, 0.20 and 0.25 mol%) samples were prepared using conventional solid-state method. Nanostructural, magnetic, ferromagnetic, dielectric, ferroelectric and electrical properties of the prepared samples were investigated. X–ray diffraction (XRD) patterns show the formation of BiBaFeO3 with single-phase hexagonal unit cell structure. The particles sizes were found to be in the range 20–33 nm. Scanning electron microscope (SEM) revealed the nanostructure consisting of small, randomly oriented and non-uniform grains. The formation of BiBaFeO3 multiferroic nanoparticles is confirmed from Fourier transform infrared (FTIR) spectra and the values of optical phonon frequency (o) were found to be (1.313–1.334) × 1013 Hz. Transmission electron microscope (TEM) for x = 0.20 mol% as a representative sample clarify that the particles were crystallized in small nanoparticles ranged from 22–28 nm. Spin canting and impurity phase could be a probable reason for the origin of ferromagnetism. Néel temperature (TN ) was observed around 743– 834 K. The dielectric properties were affected by the properties of the substitutional ions as well as the crystalline structure of the present samples. Curie temperature (TC ) was observed around 1121–1189 K. Substitution with Ba2+ ions also improved the ferroelectric polarization with remanent magnetization polarization of 89 C/cm2 . Dc conductivity shows that all samples are semiconductor and the maximum conductivity was found at x = 0.15 mol%. This maximum conductivity may be attributed to the decrease in grain boundary scattering due to the reduction in crystallite size. The calculated activation energy for the multiferroic nanoparticles were found to be 0.413–0.929 eV. The conduction was confirmed to obey non-adiabatic small polaron hopping (SPH). The electron–phonon interaction coefficient (p) was calculated and found to be in the range of (12.79–27.21). The hopping carrier mobility varied from 1.85 × 10–7 cm2V–1 s –1 to 8.01 × 10–13 cm2V–1 s –1 at 418 K. The conductivity was primarily determined by hopping carrier mobility. At intermediate temperature, the Greaves VRH (variable–range hopping) model was found to be appropriate. Ac electrical conductivity as a function of frequency as well as temperature is reported for all BiBaFeO3 multiferroic nanoparticles, which exhibit strong dependence on frequency with conduction mechanism is the correlated barrier hopping (CBH) model. The simultaneous occurrence of ferromagnetism and ferroelectric hysteresis loops at BiBaFeO3 multiferroic nanoparticles system specially for (x = 0.15 mol%) at room temperature makes it a potential candidate for information storage.