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In this communication, we report the preparation and properties of nano-CoFe2O4 by gel combustion in presence of KCl and subsequent heat treatments. The products were characterized by X-ray diffraction, Infrared spectroscopy, and Mössbauer Spectroscopy. Spinel type structure with all Fe in 3+ oxidation states was confirmed from the XRD and Mossbauer spectroscopy. The average crystallite sizes of the studied samples were about 6 and 50 nm. Low temperature magnetic and dielectric properties of the samples were studied by superconducting quantum interference device magnetometry and ac-impedance spectroscopy. The field and temperature dependent magnetization studies indicated superparamagnetic nature for 6 nm sample and ferromagnetic nature for 50 nm sample. The temperature-dependent dielectric properties measured over a wide range of frequencies indicated an increasing trend of dielectric permittivity with the decrease in crystallite size. Variable range polaron hopping conduction was observed in both samples.

High‐pressure XRD and Raman spectroscopy on orthorhombic InVO4 (space group Cmcm, Z = 4) reveal the existence of a new wolframite‐type polymorph of InVO4 near 7 GPa.

We report the effect of annealing atmosphere on structure and magnetic and dielectric properties of double perovskite-type EuCo0.5Mn0.5O3 (ECMO). Polycrystalline samples prepared by high-temperature reaction were subjected to annealing in different oxygen partial pressures and investigated by powder X-ray diffraction, magnetometry, and ac impedance spectroscopy. While the samples annealed in air or oxygen environment were found to have cation-disordered orthorhombic structure (Pnma), the samples annealed in inert atmosphere have Eu3+ deficient perovskite-type structure. The temperature- and field-dependent magnetizations indicate the ferromagnetic transition around 130 K. The differences in field-cooled and zero-field-cooled magnetization and significant effect of magnetic field on magnetic properties suggest metamagnetic behavior in ECMO. Randomly distributed clusters of ferromagnetically (FM) and antiferromagnetically (AFM) paired magnetic ions and their relative proportions are reflected in their magnetic properties. The weak nature of the antiferromagnetic interactions is reflected in the switching of AFM to FM state at appreciably lower field strength (∼300 Oe). Dielectric measurements indicate that the samples annealed in air or oxygen show large dielectric permittivity (≥2000) compared to that in inert atmosphere (∼400). The analyses of temperature- and frequency-dependent loss tangent and modulus data revealed two different types of relaxations which possibly originate from two polaronic conduction processes.

A facile surface hydroxylation treatment to modify the surface of nickel nanoparticles dispersed in ferroelectric polyvinylidene fluoride (PVDF) is reported. A remarkable increase in the amount of polar β phase of PVDF has been observed upon dispersion of nickel nanoparticles in the PVDF matrix. The leakage current reduces drastically in the composite with surface-modified nickel nanoparticles. This improvement has been observed with concurrent enhancement of electrical polarization in the surfacemodified nickel−PVDF composite. However, the magnetic moment of the modified composite is found to be slightly lower than that of the unmodified composite. Most importantly, the composite with surface-modified nickel exhibits magnetodielectric coupling significantly higher than that of the unmodified composite. The magnetodielectric coupling appears to be facilitated by surface hydroxyl groups on nickel. These results establish the potential of facile surface functionlization of nanoparticles toward the design of nanocomposites with higher magnetoelectric coupling.