We report the synthesis of undoped and Sc3+-doped BiFeO3 nanoparticles using the sonochemical technique. X-ray diffraction reveals that all samples are single phase with no impurities detected. EDX analysis was done to confirm the extent of Sc3+ doping in the samples. The size and morphology of the nanoparticles have been analyzed using transmission electron microscopy (TEM). XPS studies were done to check the presence of Fe2+ ions in the samples. The BiFeO3 nanoparticles show a weak ferromagnetic behavior at room temperature, which is quite different from the linear M–H relationship reported for bulk BiFeO3. The substitution of Sc ions for Bi enhances the ferromagnetic as well as ferroelectric properties of this system, which is mainly attributed to the antiferromagnetic core and ferromagnetic surface of the nanoparticles, together with the mild structural distortion. Temperature and field dependence of magnetization curves reveal the frustrated magnetic behavior of this system. The leakage current is considerably reduced, and electric polarization increases significantly in the case of BiFe0.95Sc0.05O3 nanoparticles. Magnetoelectric coupling was observed in the BiFe0.95Sc0.05O3 sample. Thus, it can be inferred that Sc3+-doped BiFeO3 nanoparticles show promise as good multiferroic materials.

In this study we report the synthesis of BiFeO(3) nanorods using a sonochemical technique. The nanorods had a diameter of 20-50 nm, a length of 100-500 nm and exhibit aspect ratios in the range of 5-10. However, after doping, the TEM images of Bi(0.9)Ba(0.1)Fe(0.9)Mn(0.1)O(3) and Bi(0.9)Ca(0.1)Fe(0.9)Cr(0.1)O(3) samples show that the aspect ratios of both the double doped samples have reduced considerably, while retaining the crystallinity of the particles. BiFeO(3) nanorods show a weak ferromagnetic order at room temperature, which is quite different from the linear M-H relationship reported for bulk BiFeO(3). The saturation magnetization of these BiFeO(3) nanostructures has been found to increase on doping with various metal ions (Ba(2+), Ca(2+), Mn(2+), Cr(3+)), reaching a maximum value of 1.35 emu g(-1) for the Bi(0.9)Ba(0.1)Fe(0.9)Mn(0.1)O(3) nanostructures. However, saturation of electric polarization was observed only in case of the Bi(0.9)Ca(0.1)Fe(0.9)Cr(0.1)O(3) nanostructures.

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In this paper we report the magnetic properties of nanosized CoO particles, prepared from sonochemically synthesized precursors and characterized using x-ray diffraction (XRD), conventional transmission electron microscopy (TEM) and scanning tunneling electron microscopy combined with energy dispersive x-ray analysis (STEM-EDX) techniques. The nanoparticles were faceted and the sizes varied between 30 and 60 nm depending on the time of annealing. They were stable even in the absence of any organic coating on them. Magnetic measurements reveal the presence of ferromagnetic interactions at low temperatures in the CoO nanoparticles synthesized after 2 and 4 h of annealing of the sonochemically synthesized precursor under nitrogen. However, after 6 h of annealing, the nanoparticles show hysteresis not only at low temperatures (1.5 K) but also at higher temperatures (100 K and room temperature), indicating the presence of room temperature ferromagnetism.

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