Multiferroism in multifunctional rare earth metals-doped BiFeO3 nanostructures

Abstract

In the development towards device miniaturization and high-density data storage system, it becomes highly desirable to integrate multifunctions in a single material. Multifunctional materials are the demand of future technology. Nanoscience environment provides more platforms to explore multifunctionality nanostructured multiferroics. Bismuth ferrite (BiFeO3) is hitherto the most studied multiferroic material as well as so far the only known single compound exhibiting room temperature multiferroism. However, BiFeO3 is not explored for practical device applications due to several issues such as high leakage current density, secondary phase impurities, chemical fluctuations, low magnetoelectric coupling, and also the inhomogeneous magnetic spin structure. These issues should be resolved before realization in devices. Efforts have been made to overcome the above problems using substitution. These may lower the leakage current density, oxygen vacancies, and enhances the multiferroism properties. But the cancellation of magnetism due to spiral spin structure, with an incommensurate spiral period of 62 nm superimposed on the antiferromagnetic ordering, and the low magnetoelectric coupling, are still challenges of this field. The incommensurate spiral spin structure and antiferromagnetic ordering in BiFeO3 can be broken and high magnetoelectric coupling may be achieved if the size of the BiFeO3 nanostructure should be less than that of the spin-spiral period, i.e., <62 nm, and simultaneously doping of rare earth metal ions will further enhance magnetoelectric coupling.Therefore, this thesis focuses the synthesis of BiFeO3 nanostructures viz., nanoparticles and nanowires, and study of their multiferroic properties. The doping of rare earth metal ions (Gd3+, Tb3+, Dy3+) has been done, and, the effect of doping and reduced size of BiFeO3 nanostructures (< 62 nm) on their structural, magnetic, electric, dielectric and multiferroics properties, presented.