In the present work, the effect of Dy3+ substitution on the structural and magnetic properties of CoFe2-xDyxO4 (x = 0.00 to 0.1 in step of 0.025) system synthesized by solution combustion method were investigated. The thermal decomposition process was investigated by means of differential and thermal gravimetric analysis that showed that the precursor could yield the final product after calcination above 600 °C. The phase purity and crystal lattice symmetry were estimated from X-ray diffraction studies. The microstructural features were observed by scanning electron microscopy that demonstrates the fine clustered particles with an increase of average grain size with Dy3+ content. The existence of constituent’s, i.e., Co, Fe, and Dy were authenticated by energy dispersive X-ray analysis. An infrared spectroscopy study shows the presence of two absorption bands in the frequency range around 590 cm−1 (ν1) and around 480 cm−1 (ν2); which indicate the presence of tetrahedral and octahedral group complexes, respectively, within the spinel lattice. Room temperature magnetization measurements showed that the saturation magnetization and hysteresis losses (coercivity) decreases with Dy3+ addition, which implies that these materials may be applicable for magnetic data storage and recording media.

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Novel high-κ thin composite films with excellent breakdown strength were synthesized using nonhydrolytic sol-gel processing. Organic-inorganic hybrid materials with high electronic polarizability were prepared as the matrix material to form a covalently bonded interface with the organically modified barium titanate (TBT) nanoparticles through a chemical cross-linking reaction. To enhance the dispersion stability of barium titanate (BT) nanoparticles in the matrix, the chemical nature of their surfaces was modified using diethyl 3-(trimethoxysilyl)propyl phosphonate (TMSP), which was synthesized by the Michaelis-Arbuzov reaction of chloropropyltrimethoxysilane (CPTMS) with 3-triethyl phosphate (TEP). A high degree of dispersion of the dielectric BT nanoparticles significantly improved the dielectric properties of the final composite films. Because the matrix consists of both silane and halogenated bisphenol A moieties with high electronic polarizability, adjusting the chemical composition allowed tailoring of the dielectric and film properties of the final composite materials.

We report a strain-induced magnetoelectric coupling in BaTiO3/Fe3O4 ferroelectric core/ferrimagnetic shell nanoparticles. The temperature-dependent magnetoresistance and magnetization clearly show several jumps near the structural phase transition temperatures of BaTiO3. Below the Verwey transition temperature of Fe3O4, i.e., at 20 K, the dielectric constant of BaTiO3/Fe3O4 decreases continuously upon application of an external magnetic field, and the observed magnetodielectric curve does not follow the square of the magnetization. We discuss the effect of strain on the electric field-dependent magnetic anisotropy near the core/shell interface.

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