Synthesis and Magnetic Properties of Pure and Cobalt-Doped Nanocrystalline Bismuth Ferrite
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1256-N06-14
Synthesis and Magnetic Properties of Pure and Cobalt-Doped Nanocrystalline Bismuth Ferrite Gina Montes1, Oscar Perales-Pérez2, Boris Renteria2 and Marco Galvez3 1
University of Puerto Rico, Department of Mechanical Engineering, P.O. Box 9045, Mayagüez, P.R. 00681-9045. 2 University of Puerto Rico, Department of Engineering Science and Materials, P.O. Box 9044, Mayagüez, P.R. 00681-9044. 3 University of Puerto Rico, Department of Physics, P.O. Box 9000, Mayagüez, P.R. 00681-9000.
ABSTRACT Applications of nanocrystalline multiferroics in sensor development, massive memory storage or in the fabrication of new devices taking advantage of the electron charge and spin explains the need of investigating various options to synthesize these types of materials. Among promising candidates, Bismuth ferrite (BiFeO3) is a multiferroic material that exhibits ferromagnetism, ferroelectricity and ferroelasticity. The present research is focused on the systematic study of the polyol synthesis of substrate-less nanocrystalline BiFeO3 particles and its structural and magnetic characterization. As an attempt to explore the possibility of tuning the ferrite magnetic properties, host BiFeO3 was doped with cobalt ions in the 5at. % -10at. % range. Our results suggested that the ferrite formation and its properties were strongly dependent on both, the annealing conditions of the precursors and the concentration of cobalt species. Well-crystallized pure BiFeO3 was produced after annealing the precursor powders for one hour at 800οC. Doping with cobalt ions lowered the temperature at which the nanocrystalline BiFeO3 host structure was developed. The saturation magnetization and coercivity in the nanocrystalline ferrite were strongly influenced by the selected annealing temperatures and dopant concentration. These magnetic parameters varied from 0.30 emu/g and 109.5 Oe up to 4.2 emu/g and 988 Oe for pure and 10 at % Codoped ferrite, respectively.
INTRODUCTION Multiferroic materials, which offer the possibility of manipulating their magnetic state by an electric field or viceversa, are of current interest for a broad scope of applications including actuators, switches, magnetic field sensors and new types of electronic memory devices [1]. The term ‘‘multiferroic’’ indicates the coexistence of ferroelectric and magnetic ordering in one single phase or multiphase materials [2]. Among different multiferroics candidates, BiFeO3 is a non-centro symmetric rhombohedral perovskite transition metal oxide that crystallizes in the space group R3c with a = 5.58Å and c = 13.88Å [3]. This ferrite is expected to exhibit ferromagnetism,
ferroelectricity and ferroelasticity. Since the ability to couple to either the electric or the magnetic polarization would allow an additional degree of freedom in multiferroics-based device designs, the viability of tuning the multiferroic properties of BiFeO3 by appropriate cationic substitutions would be desirable [4]. Although many efforts have been made to synthesize BiFeO3, the main challenge has been t
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