Title: Multiferroic nanocrystalline BiFeO3 and BiCrO3 thin films prepared by ion beam sputtering

Authors: P. Couture; G.V.M. Williams; J. Kennedy; J. Leveneur; P.P. Murmu; S.V. Chong; S. Rubanov

Addresses: National Isotope Centre, GNS Science, 30 Gracefield Road, P.O. Box 31312, Lower Hutt 5010, New Zealand; School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington 6140, New Zealand; The MacDiarmid Institute for Advanced Materials and Nanotechnology, SCPS, P.O. Box 600, Wellington 6140, New Zealand ' School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington 6140, New Zealand; The MacDiarmid Institute for Advanced Materials and Nanotechnology, SCPS, P.O. Box 600, Wellington 6140, New Zealand ' National Isotope Centre, GNS Science, 30 Gracefield Road, P.O. Box 31312, Lower Hutt 5010, New Zealand; The MacDiarmid Institute for Advanced Materials and Nanotechnology, SCPS, P.O. Box 600, Wellington 6140, New Zealand ' National Isotope Centre, GNS Science, 30 Gracefield Road, P.O. Box 31312, Lower Hutt 5010, New Zealand ' National Isotope Centre, GNS Science, 30 Gracefield Road, P.O. Box 31312, Lower Hutt 5010, New Zealand ' The MacDiarmid Institute for Advanced Materials and Nanotechnology, SCPS, P.O. Box 600, Wellington 6140, New Zealand; Robinson Research Institute, Victoria University of Wellington, P.O. Box 33436, Lower Hutt 5046, New Zealand ' University of Melbourne, Bio 21 Institute, Melbourne, Victoria 3010, Australia

Abstract: 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.

Keywords: multiferroic thin films; ion beam sputtering; superparamagnetic behaviour; particle size; magnetisation; BiFeO3 nanoparticles; bismuth ferrite; nanocrystalline thin films; BiCrO3; thermal annealing; nanotechnology.

DOI: 10.1504/IJNT.2017.082445

International Journal of Nanotechnology, 2017 Vol.14 No.1/2/3/4/5/6, pp.56 - 65

Published online: 23 Feb 2017 *

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