Magnetic and hyperfine properties of nanostructured Cu_1-xFe_xO

In this investigation, the Fe-doped CuO system was prepared by freeze-drying an aqueous solution of copper and iron acetates, followed by a heat treatment. The synthesized samples, which were previously identified as monophasic and nanostructured, were then characterized by Mössbauer spectroscopy and magnetization techniques. These nanoparticles revealed a complex magnetic behavior, which can be attributed to the presence of two different magnetic regions: the particle core, characterized by antiferromagnetic fluctuations, and the particle shell, in which uncompensated spins are responsible for the superparamagnetic character and, eventually, the ferromagnetic interaction among the nanoparticles at low temperatures. The ferromagnetism observed for this system shows that antiferromagnetic oxide matrixes can be used for diluted magnetic semiconductor applications, if suitably doped.