Hilal Ahmad Reshi

Nanostructured La0.7Sr0.3MnO3 compounds for effective electromagnetic interference shielding in the X-band frequency range

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.

X-band frequency response and electromagnetic interference shielding in multiferroic BiFeO3 nanomaterials

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.

Kondo-like electronic transport and ferromagnetic cluster-glass behavior in La0.7Sr0.3MnO3 nanostructures

We have studied the electronic transport and magnetic properties of a nanocrystalline La0.7Sr0.3MnO3 system. The samples were prepared by sol–gel method and were sintered at different temperatures to achieve few nanometre grain sizes. The temperature dependent resistivity revealed Kondo like electronic transport at low temperature (T < 50 K) and variable range hopping in the paramagnetic insulating regime under zero and high magnetic field. The reduced grain size sample showed marginal increase in electrical resistivity. The temperature-field dependent ac-susceptibility measurement indicated the FM-cluster formation. A neck like magnetic hysteresis loop was observed due to the competition between ferromagnetic core and paramagnetic shell. The ferromagnetic clusters with paramagnetic interfaces impart glassy behavior.

Enhanced magnetization in morphologically and magnetically distinct BiFeO3 and La0.7Sr0.3MnO3 composites

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 sol-gel method. Composites with nominal compositions (1−x)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 ...

Investigation on gas sensing properties of Ag doped BiFeO3

Bismuth ferrite (BFO) and Ag substituted Bismuth ferrite with perovskite structure have been synthesized using sol-gel method and investigated for their gas sensing properties. Single phase and rhombohedral crystal structure of the samples were confirmed from XRD pattern. Oxidation state of the elements is confirmed using X-Ray Photoelectron Spectroscopy (XPS). Since Ag substituted Bismuth ferrite exhibited pronounced response to H2S gas as compared to other gases, H2S gas sensing properties of Bismuth ferrite (BFO) and Ag substituted Bismuth ferrite were investigated in detail. Bi0.9Ag0.1FeO3 (BAFO) exhibits enhanced sensitivity, quick response and selectivity towards H2S as compared to BFO.Bismuth ferrite (BFO) and Ag substituted Bismuth ferrite with perovskite structure have been synthesized using sol-gel method and investigated for their gas sensing properties. Single phase and rhombohedral crystal structure of the samples were confirmed from XRD pattern. Oxidation state of the elements is confirmed using X-Ray Photoelectron Spectroscopy (XPS). Since Ag substituted Bismuth ferrite exhibited pronounced response to H2S gas as compared to other gases, H2S gas sensing properties of Bismuth ferrite (BFO) and Ag substituted Bismuth ferrite were investigated in detail. Bi0.9Ag0.1FeO3 (BAFO) exhibits enhanced sensitivity, quick response and selectivity towards H2S as compared to BFO.

Modulation of magnetic interaction in Bismuth ferrite through strain and spin cycloid engineering

Bismuth ferrite, a widely studied room temperature multiferroic, provides new horizons of multifunctional behavior in phase transited bulk and thin film forms. Bismuth ferrite thin films were deposited on lattice mismatched LaAlO3 substrate using pulsed laser deposition technique. X-ray diffraction confirmed nearly tetragonal (T-type) phase of thin film involving role of substrate induced strain. The film thickness of 56 nm was determined by X-ray reflectivity measurement. The perfect coherence and epitaxial nature of T- type film was observed through reciprocal space mapping. The room temperature Raman measurement of T-type bismuth ferrite thin film also verified phase transition with appearance of only few modes. In parallel, concomitant La and Al substituted Bi1-xLaxFe0.95Al0.05O3 (x = 0.1, 0.2, 0.3) bulk samples were synthesized using solid state reaction method. A structural phase transition into orthorhombic (Pnma) phase at x = 0.3 was observed. The structural distortion at x = 0.1, 0.2 and phase transition at x = 0.3 substituted samples were also confirmed by changes in Raman active modes. The remnant magnetization moment of 0.199 emu/gm and 0.28 emu/gm were observed for x = 0.2 and 0.3 bulk sample respectively. The T-type bismuth ferrite thin film also showed high remnant magnetization of around 20emu/cc. The parallelism in magnetic behavior between T-type thin film and concomitant La and Al substituted bulk samples is indication of modulation, frustration and break in continuity of spiral spin cycloid.

Synthesis of ZnSnO3 nanostructure by sol gel method

Zinc Stannate (ZST) with composition ZnSnO3 is known for high electron mobility, optical, piezoelectric and charge storage properties. ZST crystalizes in different lattice structures, which allows a wide range of tunablity. We demonstrate successful synthesis of ZnSnO3 nanomaterial by sol-gel method. ZnSnO3 nanomaterials were calcined and sintered at different temperatures. Powder X-ray diffraction confirmed the single phase of the nanomaterial with rhombohedral R-3 space group. The Rietveld refinement of diffraction pattern yielded lattice parameter values a=5.26A, c=14.09A. Raman spectroscopy revealed higher activity towards higher wavenumbers. Raman shift around 530cm−1 was found to be highly structure dependent, most probably due to anharmonic atomic vibrations in ZnO6/SnO6 octahedra around center of mass. Sharp Peak around 650cm−1 is characteristic of ZnSnO3 molecule.