K.N. Rathod

Size-controlled electrical properties of sol–gel-grown nanostructured Gd0.95Ca0.05MnO3

In this communication, we report the results of the studies on electrical properties of cost-effective modified sol–gel-grown nanostructured Gd0.95Ca0.05MnO3 (GCMO) manganites sintered at different temperatures. Structural investigations, carried out using X-ray diffraction measurements, reveal the single-phasic nature of GCMO samples having orthorhombic unit cell structure. Frequency-dependent variation in AC conductivity (σAC) has been discussed on the basis of correlated barrier hopping (CBH) mechanism for the GCMO samples sintered at lower temperatures. Sintering temperature-induced transition from CBH mechanism to Maxwell–Wagner relaxation processes has been discussed in detail. Size-induced modifications in the impedance response of the samples have been understood, in detail, using size effects and Cole–Cole plots.Graphical Abstract

Magnetoelectric properties of Co-doped BiFeO3 nanoparticles

The magnetoelectric (ME) properties of sol–gel grown BiFe0.95Co0.05O3 (BFCO) nanoceramics, with different sizes, were investigated at room-temperature. X-ray diffraction (XRD) measurement was performed to investigate structural properties of the samples understudy. Magnetic field-dependent dielectric permittivity has been systematically investigated in the frequency range of 20xa0Hz to 1xa0MHz. To ensure the origin of magnetodielectric response, the magnetoimpedance (MI) spectroscopy was adopted using equivalent circuit model. The a.c. conductivity was found to obey the Jonscher’s universal power law. The modifications in spiral spin structure in the BFCO nanoparticles with size less than ∼62xa0nm significantly affect the ME coupling parameters.

Structural and Transport Studies on Mixed Valent Rare Earth Manganite Ceramics

ABSTRACT La0.5Pr0.2Ca0.3–xBaxMnO3 (LPCBMO) (x = 0.05, 0.10, 0.15, 0.20, 0.25, 0.30) ceramic manganites have been successfully synthesized by conventional solid state reaction method. Structural studies have been carried out by performing X-ray diffraction measurements and Rietveld refinements. Obtained value of crystallite size varies from 76 nm in lower doped sample (x=0.05) to 13 nm in the sample doped with x=0.30. Variation in crystallite size with x has been discussed in the context of size mismatch at A-site cationic lattice and structural disorder. In addition, all the samples exhibit metal to insulator transition at TP which gets increased with increase in Ba-content (x). Effect of crystallite size and other structural parameters on the transport properties of LPCBMO samples has been discussed in detail in the light of competition between the structural disorder and tolerance factor and shown that the tolerance factor can effectively modify the transport behaviour in manganites. Below 50 K, all the R-T plots of LPCBMO system show resistivity minimum behaviour which gets modified by Ba-content. This behaviour has been discussed in detail on the basis of electronelectron interaction having the form: ρ = [1/(σ0+BT1/2)]+ρnTn. GRAPHICAL ABSTRACT