INVESTIGADORES
STEREN Laura Beatriz
congresos y reuniones científicas
Título:
Oxygen vacancies and magnetic properties of polycrystalline CeO2
Autor/es:
ALEJANDRO, G; PAULIN, M., SACANELL, J., STEREN, L.B., AND LEYVA, G.
Lugar:
Buenos Aires
Reunión:
Conferencia; X Latin-American Workshop on Magnetism, Magnetic Materials and their Applications; 2013
Resumen:
Oxygen vacancies and magnetic properties
of polycrystalline CeO2
Alejandro, G.,1 Paulin, M.,2 Sacanell, J.,2
Steren, L.B.,2 and Leyva, G.2
1Centro Atomico Bariloche (CNEA). Av. Bustillo 9500,
(8400) San Carlos de Bariloche, Pcia. de Rio Negro.
Argentina
2Centro Atomico Constituyentes (CNEA). (1650) San
Martin, Pcia. de Buenos Aires, Argentina.
Cerium dioxide is a wide gap semiconductor with
uorite structure widely used for catalysts. It has recently
been proposed as a diluted magnetic semiconductor
(SMD) for spintronic applications by slightly
doping it with magnetic ions such as Co, Fe, Mn, etc.
In this work we investigate the role of oxygen vacancies
in the parent, undoped compound CeO2 by electron
spin resonance (EPR) and magnetization experiments.
Pure CeO2 powders were synthesized by the liquidmix
method using 99.99% Ce(NO3):6H2O. The samples
were calcined in air at 600 C. The X-ray diraction
analysis indicates a
uorite structure with no secondary
phases. The CeO2 powders so obtained were
subsequently annealed at 500 C in an low oxygen
content atmosphere, under a pressure of 2 10 2 mbar.
These treatments were applied for 5 hs, 10 hs, 15 hs,
and 20 hs with the aim of introducing an increasing
amount of oxygen vacancies in a controlled way.
Magnetization vs. eld measurements were performed
in a QD Versalab VSM showing an increase of
the magnetic signal for samples annealed at low oxygen
pressures. The EPR experiments were done at
room temperature in a Bruker ESP-300 spectrometer
using a microwave frequency of 9.7 GHz (X-band). In
all the cases, the annealed samples revealed an EPR
spectrum consisting of a single line close to g = 2.
Interestingly, we observed that the intensity of the
EPR signal increases almost linearly with increasing
annealing time. In other words, the number of paramagnetic
centers that are at the origin of the EPR
absorption is directly correlated with the number of
oxygen vacancies. We compare the EPR and magnetization
results, and discuss them in terms of Ce 3+
and oxygen vacancies contents and the nature of the
magnetic interactions present in the compound.