title: Identifying defects in multiferroic nanocrystalline BaTiO(3) by positron annihilation techniques.
abstract: Room temperature ferromagnetism in nanoparticles of otherwise nonmagnetic materials has been attributed to point defects at the surface of the nanoparticles. Here, we have employed positron annihilation spectroscopy to identify the nature of defects in multiferroic BaTiO(3) nanocrystalline materials with varying average particle sizes. Ratio curve analysis of the Doppler broadening profile to a reference profile suggests that the defect is an oxygen vacancy. The decrease of intensity of the intermediate lifetime component with increasing particle size indicates a decrease of surface defect concentration. The large defect concentration in nanocrystalline BaTiO(3) can explain the observed room temperature ferromagnetism.
authors.affiliation: Chemistry and Physics of Materials Unit, Department of Science and Technology Unit on Nanoscience, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur PO, Bangalore 560064, India.
authors.forename: R V K
authors.initials: RV
authors.lastname: Mangalam
authors.forename: Mahuya
authors.initials: M
authors.lastname: Chakrabrati
authors.forename: D
authors.initials: D
authors.lastname: Sanyal
authors.forename: A
authors.initials: A
authors.lastname: Chakrabati
authors.forename: A
authors.initials: A
authors.lastname: Sundaresan