Ratnamala Chatterjee

Electromagnetic and microwave absorption properties of (Co2+-Si4+) substituted barium hexaferrites and its polymer composite

The electromagnetic (EM) and microwave absorption properties of (Co2+–Si4+) substituted barium hexaferrite compositions BaCox2+Fey+2Six+y4+Fe12−2x−2y+3O19 (x=0.9 and y=0.0, 0.05, and 0.2) and its polymer composites prepared from hexaferrite, polyaniline, and carbon powders dispersed in polyurethane matrix have been investigated at the microwave frequency range of the X band (8.2–12.4GHz). The hexaferrite compositions were synthesized by solid-state reaction technique, whereas polyaniline, by chemical route. The permeabilities of a ferrite are drastically reduced at higher gigahertz frequencies. The permittivities, however, can be enhanced by appropriate choice of composition and processing temperature. In the present ferrite composition, silicon content is taken in excess so as to convert some of the Fe3+ ions to Fe2+ ions. This conversion has been shown to enhance EM and absorption properties. Mossbauer spectroscopy on the samples establishes that addition of excess Si4+ converts some of the Fe3+ to Fe2+...

Enhanced magnetoelectric coefficient (α) in the modified BiFeO3–PbTiO3 system with large La substitution

Magnetoelectric coupling coefficient (α) values of 0.88mV∕cm∕Oe at 200Oe and magnetocapacitive effects are reported in solid-solution BF–LF–PT with large La substitution (50:50 in BF). Enhancement of magnetic, dielectric, and ferroelectric properties is also observed. The solid solution shows relaxor behavior with large permittivity values (∼30000), large remnant polarization (∼61μC∕cm2), and symmetric but nonsaturating M-H loop with Mr∼0.25emu∕g.

Structural, electrical, and strain properties of stoichiometric 1−x−y(Bi0.5Na0.5)TiO3−x(Bi0.5K0.5TiO3)−y(Na0.5K0.5)NbO3 solid solutions

Results on two series of lead-free piezoelectric solid solutions of 1−x−y(Bi0.5Na0.5)TiO3−x(Bi0.5K0.5TiO3)−y(Na0.5K0.5)NbO3 (BNT-BKT-KNN) ceramics, synthesized in the vicinity of ferroelectric rhombohedral (x=0.17) and ferroelectric tetragonal (x=0.20) phase boundary of 1−x(BNT)–xBKT are presented. Orthorhombic KNN in stoichiometric proportion as third component with 0.0≤y≤0.06 is added to prepare these two series (i) with x=0.17 and (ii) with x=0.20. Addition of KNN up to a critical y is observed to improve tetragonality in both series and solid solubility of KNN was verified at least up to y=0.1 in this system. Depolarization temperature Td of these stoichiometric BNT-BKT-KNN series were found to be considerably lower than that of their parent BNT-BKT compositions. As a result of this, coexistence of polar and nonpolar phases for compositions at morphotropic phase boundary (MPB) were indicated at room temperature, resulting in pinched polarization versus electric field (P-E) loops and large strain (stra...

Improved magnetoelectric coupling in Mn and Zn doped CoFe2O4–PbZr0.52Ti0.48O3 particulate composite

In this letter, Mn and Zn simultaneously substituted CoFe2O4, Co0.6Zn0.4Fe1.7Mn0.3O4 has been proposed as magnetostrictive component having the maximum in plane piezomagnetic coupling coefficient (q11+q12∼0.070 ppm/Oe) at a field of H∼300 Oe with appreciable saturation values of longitudinal and transverse magnetostriction coefficients (λ11∼−20 ppm and λ12∼10 ppm). On incorporating this in composite (i.e., (x) PbZr0.52Ti0.48O3−(1−x) Co0.6Zn0.4Fe1.7Mn0.3O4) preparation, maximum magnetoelectric voltage coefficients (αE∼122 mV/cm Oe) was obtained in sample x=0.90 at ac magnetic field of amplitude ∼1 Oe and frequency ∼1 kHz.

Origin of large dielectric constant in La modified BiFeO3-PbTiO3 multiferroic

The presence of superlattice reflections and detailed analyses of the powder neutron and x-ray diffraction data reveal that La rich (BF

Magnetization induced dielectric anomaly in multiferroic LaFeO3–PbTiO3 solid solution

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Magnetic, dielectric, magnetoelectric, and microstructural studies demonstrating improved magnetoelectric sensitivity in three-phase BaTiO3–CoFe2O4–poly(vinylidene-fluoride) composite

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Thickness dependent functional properties of PbZr0.52Ti0.48O3/La0.67Sr0.33MnO3 heterostructures

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Improved electrical properties of PbZrTiO3/BiFeO3 multilayers with ZnO buffer layer

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Phonons and magnetic excitation correlations in weak ferromagnetic YCrO3

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