Investigations on the growth and Characterization of ndfeo3 single Crystals and rare earth doped Ferrite nanoparticles

Abstract

The Rare Earth Orthoferrites (RFeO3) of perovskite structure have attracted much attention owing to its wide applications in solid-oxide fuel cells, magneto-optical materials, catalysts and gas sensors. RFeO3 compounds have demanding scope due to their spin re-orientation phenomena of Fe3+ ions, where the magnetic orientation changes from one crystal axis to another, upon variations in temperature or applied magnetic field. Hence, at low temperatures of about 100-200 K, the magnetic interactions between Fe-Fe and R-Fe ions strongly compete with each other, leading to the spin re-orientation transition of the ordered Fe3+ magnetic moments. These strong magnetic interactions also give rise to exceptional magnetic properties like compensation effect (Tcomp), antiferromagnetic transition of Fe (TN1), ordering of R3+ ions (TN2) and weak ferromagnetism. They also exhibit unusually large antisymmetric exchange interactions as they belong to Dzyaloshinsky-Moriya type of canted weak ferromagnets having small anisotropy of Fe spins in a-c plane; while large anisotropy along b-axis. newlineThe thesis focuses on the growth and characterization of NdFe1+xO3 single crystals using the Optical Floating Zone technique (OFZ) and the A-site substitution of RE ions (RE=Gd, Sm) in NdFeO3 to study their structural, magnetic properties using conventional solid-state reaction method. The thesis also aims to study the size effect on the structural, magnetic and electrical properties of the RE substitution in NdFeO3 (NFO) nanoparticles by Glycine-nitrate autocombustion method. For the growth of NdFe1+xO3 single crystals, an excess amount of Fe (x=0.03 mol%) has been added to the NdFeO3 composition, in order to reduce the molten zone instability. newline