(Sn0.97–x
Sb0.03Fe
x
)O2 films (x =
0, 0.024, 0.046, and 0.073) were prepared by radio frequency magnetron
sputtering. The structural environment, electrical transport, and
magnetic behavior of the films were studied by X-ray diffractometer,
X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge
structure, physical property measurement system, electron paramagnetic
resonance (EPR), and superconducting quantum interference methods.
All of the films exhibited the tetragonal rutile structure of SnO2 by X-ray diffraction. XPS and extended X-ray absorption fine
structure measurements revealed that Fe-doping ions substitute for
Sn4+ sites of SnO2 lattice with a mixed-valence
(Fe2+/Fe3+) and no trace of Fe cluster or second
phases are in the doped system. The electrical transport measurement
showed that the films have a typical semiconductor characteristic
and that the carrier concentration n
c decreases
monotonically with Fe-doped concentration, and the carriers are strongly
localized. Magnetic measurement showed that the saturation magnetization
of the films increases regularly with Fe-doped concentration at room
temperature. On the basis of EPR analysis, with an increase of Fe-doped
concentration, the number of oxygen vacancies (Vo
+) increases. The oxygen vacancies result in a long-range ferromagnetic
ordering of the codoped SnO2 films. The origin of ferromagnetism
of the codoped SnO2 films can be attributed to bound magnetic
polaron mechanism.
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