Some peculiarities in the magnetic behavior of aerosol generated NiO nanoparticles

• Structural and magnetic characterization of cubic-shaped aerosol NiO nanoparticles.
• Procedure for subtracting an underlying diamagnetic contribution.
• Correlation between specific surface area of NPs and their diamagnetic susceptibility.
• Critical transition temperature associated to a hypothetical superconductive state.

Nickel oxide nanoparticles (NPs) 6–24 nm size have been prepared by a levitation-jet method based on metal vapor condensation in a mixture of gaseous streams of helium and air (or oxygen). Particles were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) N2 adsorption and SQUID magnetometry. It is revealed that at room-temperature (RT) the nanoparticles show a small magnetic moment and the magnetic field dependence of their susceptibility a minimum lying below the high-field values. After the appropriate subtraction of both ferromagnetic and paramagnetic components from the initial magnetization curves, the appearance of a diamagnetic contribution is observed. The possible link between the latter contribution and the occurrence of some features related to RT superconductivity in NiO NPs is discussed.

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