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.

Room temperature angle-dispersive x-ray diffraction measurements on zircon-type ${\text{EuVO}}_4$, ${\text{LuVO}}_4$, and ${\text{ScVO}}_4$ were performed up to 27 GPa. In all the three compounds we found evidence of a pressure-induced structural phase transformation from zircon to a scheelite-type structure. The onset of the transition is near 8 GPa, but the transition is sluggish and low-pressure and high-pressure phases coexist in a pressure range of about 10 GPa. In ${\text{EuVO}}_4$ and ${\text{LuVO}}_4$ a second transition to a $M$-fergusonite-type phase was found near 21 GPa. The equations of state for the zircon and scheelite phases are also determined. Among the three studied compounds, we found that ${\text{ScVO}}_4$ is less compressible than ${\text{EuVO}}_4$ and ${\text{LuVO}}_4$, being the most incompressible orthovanadate studied to date. The sequence of structural transitions and compressibilities are discussed in comparison with other zircon-type oxides.