  The origin of ferromagnetism in nanoparticles of nonmagnetic oxides is an
interesting area of research. In the present work, transport properties of
niobium thin films, with beta-Ga2O3 nanoparticles embedded within them, are
presented. Nanoparticles of beta-Ga2O3 embedded in a Nb matrix were prepared at
room temperature by radio frequency co-sputtering technique on Si (100) and
glass substrates held at room temperature. The thin films deposited on Si
substrates were subjected to Ar annealing at a temperature range of 600-650 C
for 1 hour. Films were characterized by X-ray diffraction (XRD), Micro-Raman
and elemental identification was performed with an Energy Dispersive X-ray
Spectroscopy (EDS). Transport measurements were performed down to liquid helium
temperatures by four-probe contact technique, showed characteristics analogous
to those observed in the context of a Kondo system. A comparison of the
experimental data with the theoretical formalism of Kondo and Hamann is
presented. It is suggested that this behavior arises from the existence of
magnetic moments associated with the oxygen vacancy defects in the
nanoparticles of the nonmagnetic oxide Ga2O3.
