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BiFeO3–graphene oxide (BFO–GO) nanocomposites were synthesized through ultra-sonication under mild heating, and their electromagnetic interference (EMI) shielding performance was investigated. The nanocomposites preserve the crystalline phase with R3c symmetry as analyzed by Rietveld refinement of x-ray diffraction data. The Raman spectroscopy and x-ray photoelectron spectroscopy studies confirm the formation of structured GO in nanocomposites samples. Magnetic hysteresis curves indicate unsaturated magnetic behavior. The interfacial polarization is dominating in BFO–GO composites as estimated from frequency dependent complex parameters determined in line with the Nicolson–Ross–Weir algorithm. The BFO–GO nanocomposites showed EMI shielding effectiveness of 18 dB (93% attenuation) over the measured frequency range. The oxide composite is a suitable EMI shielding material for techno-commercial applications. [ABSTRACT FROM AUTHOR]

Nanomaterials exhibit properties different from those of their bulk counterparts. The modified magnetic characteristics of manganite nanoparticles were exploited to improve magnetization in multiferroic BiFeO3 compound. We studied the composite of two morphologically and magnetically distinct compounds BiFeO3 (BFO) and La0.7Sr0.3MnO3 (LSMO). The microcrystalline BiFeO3 sample was prepared by solid state reaction method and the nanocrystalline La0.7Sr0.3MnO3 by solgel method. Composites with nominal compositions (1x→)BiFeO3-(x)La0.7Sr0.3MnO3 were prepared by modified solid state reaction method. The phase purity and crystal structures were checked by using X-ray diffraction. The formation of composites with phase separated BFO and LSMO was confirmed using Raman and Fourier Transform Infrared spectroscopy studies. The composite samples showed relatively high value of magnetization with finite coercivity. This improvement in magnetic behavior is ascribed to the coexistence of multiple magnetic orderings in composite samples. We scrutinized the possibility of oxygen vacancy or Fe mixed valency formation in the samples using X-ray photoelectron spectroscopy technique. [ABSTRACT FROM AUTHOR]

The presence of electric dipoles, magnetic dipoles and mobile charges is a prerequisite for electromagnetic interference (EMI) shielding materials. Here, we demonstrate that multiferroic compound with incipient ensemble of electric and magnetic dipoles can perform as an EMI shielding material. We synthesized single phase BiFeO3 nanomaterial and studied complex electromagnetic properties in an X-band frequency region. A shielding effectiveness up to 11 dB with a major contribution from absorption was observed in the BiFeO3 nanomaterials. An auxiliary functionality of radiation shielding is revealed in the multiferroic BiFeO3 compound. [ABSTRACT FROM AUTHOR]

We report a detailed study on the electromagnetic interference (EMI) shielding effectiveness (SE) properties in La0.7Sr0.3MnO3 (LSMO) nanomaterials. The samples were prepared by a solution chemistry (sol–gel) route at different sintering temperatures. The single-phase samples with grain sizes of 22 and 34 nm showed DC electrical conductivity variation from 0.65 to 13 S cm−1 at room temperature. The application of a high magnetic field resulted in higher conductivity values. The electrical conductivity variation with temperature could be fitted with a variable range hopping mechanism in a limited temperature range. The variation of frequency dependent electromagnetic parameters measured at room temperature within the X-band region is consistent with the electrical conductivity behavior. The complex permittivity and permeability parameters were determined in line with the Nicolson–Ross–Weir algorithm. The LSMO nanomaterial samples showed EMI shielding effectiveness values of up to 19 dB (96.3% attenuation) over the X-band frequency range, making them suitable for microwave radiation shielding in commercial and defense appliances. [ABSTRACT FROM AUTHOR]

The effect of different synthesis techniques on structural, microstructural and electrical properties of La0.7Sr0.3MnO3 (LSMO) was investigated. Two different techniques viz solid state reaction (SSR) and solgel (SG) method were used to prepare the samples. X-ray studies have confirmed the single phase formation of LSMO by both the techniques. The average grain size was 2 μm for solid state reaction sample and 22 nm for sol-gel sample. A substantial enhancement in electrical resistivity was observed in the sample with nanosized grains. The micro grain size sample exhibited metallic behaviour whereas nanoparticle sample showed metal-insulator transition around 250 K. [ABSTRACT FROM AUTHOR]

We investigated implications of nanostructure formation on structural and magnetotransport properties of La0.7Sr0.3MnO3 compound. The polycrystalline nanomaterials of variable grain sizes were synthesized by using sol-gel method. The structural parameters obtained by Rietveld refinement of the X-ray diffraction data indicated that the samples possess perovskite structure with orthorhombic Pnma symmetry. The X-ray Photoemission Spectra showed chemical shift in the lowest particle size sample due to oxygen deficiency. The average particle size observed through transmission electron microscopy varied from 22 nm to 34 nm. The particle size induced metal-insulator transition and substantial increase in electrical resistivity observed in these nanomaterials are in contrast with the bulk material phase diagram. We also observed temperature and magnetic field dependent colossal magnetoresistance. The low-field magnetoresistance is substantially enhanced in nanomaterials samples, making it more promising for device applications. A divergence in field cooled and zero field cooled magnetization indicated possibility of magnetic spin-glass behavior.