Particle size dependent magnetic properties and phase transitions in multiferroic BiFeO3 nano-particles

• Published in: Journal of alloys and compounds Vol. 543; pp. 206 - 212
• Main Authors: Annapu Reddy, V., Pathak, N.P., Nath, R.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 05.12.2012; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cycloid spin structure; Exact sciences and technology; Finite scaling effect; Magnetic; Magnetic properties and materials; Magnetic properties of nanostructures; Multiferroic; Physics; Spin polarization screening; Finite scaling effect; Magnetic; Cycloid spin structure; Spin polarization screening; Multiferroic; Grain boundaries; Finite size effect; Scanning electron microscopy; Particle size; Spray pyrolysis; Magnetization; Spray coatings; Bismuth Iron Oxides Mixed; XRD; SAED; Nanoparticles; Ferroic material; Transmission electron microscopy; Coercive force; Magnetic structure; Fourier-transformed infrared spectrometry
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2012.07.098

► Nano-particles of Bismuth ferrite was synthesized by spray pyrolysis technique at low temperature. ► Bismuth ferrite exhibits room temperature weak ferromagnetism. ► The adsorbate induced spin polarization screening in Bismuth ferrite nanoparticles. ► The superparaelectric size of Bismuth ferrite was determined. ► The phase transitions shift with particle size are discussed base on the modified Ising model. The particle size effect in the range 10–150nm on the magnetic properties and phase transitions in BiFeO3 samples prepared by spray pyrolysis method has been studied. The phase purity and structure have been investigated by XRD and FTIR spectroscopy analysis. The FTIR peaks of the nanoparticles shift to lower wave number due to increase surface area and grain boundaries. The Fe-SEM and TEM images show that the particles are uniform, dense and of nearly spherical shape nanoparticles. The significant enhancement in magnetization with finite coercive field has been observed in 12nm particle size samples. The increase in magnetization is about four times larger than that of the bulk samples. It has been attributed to the suppression of the cycloidal spin structure due to large uncompensated spins of Fe+3 ions at the surface of the particle and the adsorbate induced spin polarization screening in BFO nanoparticles. The phase transitions above room temperature have been investigated by DTA measurements and show that Néel temperature (TN) and Curie temperature (Tc) increase with particle size. The shift in TN and Tc values with particle size are fitted well to the finite scaling models. The microscopic parameters like correction length, characteristic microscopic dimension of the system and critical particle size have been evaluated which provide more physical insight in the finite scaling effect in the nanoparticle samples.