We investigated the effect of gadolinium doping (1-5 at.%) on the magnetic and dielectric properties of Fe 3 O 4 nanoparticles, synthesized by the chemical co-precipitation technique, primarily to understand the onset of multifunctional properties such as ferroelectricity and magnetodielectric coupling. The substitution of larger Gd 3+ ions at smaller Fe 3+ octahedral sites in inverse spinel Fe 3 O 4 has significantly influenced the morphology, average crystallite size, and more importantly, the magneto-crystalline anisotropy and saturation magnetization. The magnetocrystalline anisotropy and the saturation magnetization decreases substantially, however, significant increase in the average crystallite size is observed upon Gd doping. Furthermore, temperature-dependent dielectric studies suggest that these nanoparticle systems exhibit relaxor ferroelectric behavior, with much pronounced ferroelectric polarization moment recorded for 5 at.% Gd doped Fe 3 O 4 as compared to its undoped counterpart. K E Y W O R D Sferrites, ferroelectricity/ferroelectric materials, ferromagnetism/ferromagnetic materials, magnetoelectrics Suvra S. Laha and Ehab Abdelhamid contributed equally for this work.

First-principles molecular-dynamics calculations have been used to calculate the formation energy of the lowest-energy As interstitial configuration relative to the formation energies of As antisites and Ga vacancies in As-rich GaAs, and to identify and study the properties of energetically favorable complexes containing one As antisite and one As interstitial. It is suggested that the electronic and optical properties of the antisiteinterstitial complexes match the properties of the defects responsible for the dominant donor band in some samples grown around 350°C.

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A series of porous LiFeMgSiO/C (x = 0, 0.01, 0.02, 0.04) nanocomposites (LFS/C, 1Mg-LFS/C, 2Mg-LFS and 4Mg-LFS/C) have been synthesized via a solvo-thermal method using the Pluronic P123 polymer as an in situ carbon source. Rietveld refinement of the X-ray diffraction data of LiFeMgSiO/C composites confirms the formation of the monoclinic P2 structure of LiFeSiO. The addition of Mg facilitates the growth of impurity-free LiFeSiO with increased crystallinity and particle size. Despite having the same percentage of carbon content (∼15 wt%) in all the samples, the 1Mg-LFS/C nanocomposite delivered the highest initial discharge capacity of 278 mA h g (∼84% of the theoretical capacity) at the C/30 rate and also exhibited the best rate capability and cycle stability (94% retention after 100 charge-discharge cycles at 1C). This is attributed to its large surface area with a narrow pore size distribution and a lower charge transfer resistance with enhanced Li-ion diffusion coefficient compared to other nanocomposites.