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Dr Pierre Couture


Research Staff

My publications

Publications

Couture P., Williams G.V.M., Kennedy J., Leveneur J., Murmu P.P., Chong S.V., Rubanov S. (2017) Nanocrystalline multiferroic BiFeO3 thin films made by room temperature sputtering and thermal annealing, and formation of an iron oxide-induced exchange bias, Journal of Alloys and Compounds 695 pp. pp 3061-3068 Elsevier
Multiferroic nanocrystalline BiFeO3films have been successfully made by room temperature sputtering and thermal annealing in oxygen at 500ýC. Nanocrystalline Bi was seen before annealing as well asb-Bi2O3 and the iron oxide phases, magnetite, maghemite, and FeO. Superparamagnetism was observed that can be attributed to magnetite and maghemite nanoparticles. The thermally annealed film contained BiFeO3 nanoparticles and magnetite, maghemite, and hematite as well as unidentified BiFexOyphases. Superparamagnetism was also seen after annealing and the magnetic properties are predominately due to magnetite and maghemite nanoparticles rather than from multiferroic BiFeO3. The saturation magnetic moment was 60% lower after annealing, which was due to some of the Fe in the iron oxide
nanoparticles being incorporated into the BiFeO3nanoparticles. An exchange bias was observed before and after annealing that cannot be attributed to a structure that includes BiFeO3. It is likely to arise from magnetite and maghemite cores with spin-disordered shells.
Robert Carmelle, Couture Pierre, Goulet Mathieu, Drissen Laurent (2012) The Ultraviolet Imaging Telescope Onboard ASTROSAT to Study
Young Stellar Populations,
In: Drissen Laurent, Robert Carmelle, St-Louis Nicole, Moffat Anthony F. J (eds.), Four Decades of Research on Massive Stars 465 pp. 392-397 Astronomical Society of the Pacific
Starbursts are found through the whole Universe and represent an important phase in the evolution of galaxies. Distant starbursts may be easily observed and
study in the ultraviolet light because of their massive stars. I will present magnitude
and color simulations of young stellar populations in order to characterize their age,
metallicity, initial mass function, and star formation rate and history. These simulations
take into account the filters available with the Ultraviolet Imaging Telescope.
Couture P., Williams G.V.M., Kennedy J., Leveneur J., Murmu P.P., Chong S.V., Rubanov S. (2017) Multiferroic nanocrystalline BiFeO3 and BiCrO3 thin
films prepared by ion beam sputtering,
International Journal of Nanotechnology 14 (1-6) pp. pp 56-65 Inderscience Enterprises Ltd
BiFeO3 and BiCrO3 films were made by room temperature
sputtering followed by thermal annealing in a partial oxygen atmosphere.
The annealed films were found to be nanocrystalline, with an average particle
size of 11 nm for BiFeO3 and 8 nm for BiCrO3. The saturation moment per
formula unit is 0.39 µB for BiFeO3 which is significantly greater than that
found in bulk BiFeO3 (0.02 µB). A similar enhancement was also found in
previous studies of BiFeO3 nanoparticles where the nanoparticle size was
small. However, no large enhancement of the saturation moment per formula
unit was identified for the annealed BiCrO3 films. The annealed BiFeO3 films
displayed superparamagnetic behaviour and the particle size estimated from the
blocking temperature is comparable to that estimated from the X-ray diffraction
data. Our results show that sputtering and oxygen annealing is a method that
can be used to make nanocrystalline BiFeO3 and BiCrO3 films.