Study of ferromagnetism in nanostructured nonmagnetic inorganic materials

Abstract

This thesis consists of five chapters presenting magnetic properties of otherwise nonmagnetic inorganic nanomaterials which include nanoparticles, hollow spheres and doped nanoparticles. Chapter 1 gives a brief introduction of magnetism and magnetic materials. It includes important concepts and theories of magnetism. A brief review of recent developments of magnetism in nanoparticles of nonmagnetic materials has been given. Chapter 2 discusses the magnetic properties of MgO nanoparticles. Positron annihilation and photoluminescence spectroscopy were used to get the nature and concentration of defects. Effect of Li doping in the magnetic properties of MgO nanoparticles has also been studied. Chapter 3 discusses about the ferromagnetic properties of inorganic hollow spheres of otherwise nonmagnetic materials. Magnetism in these hollow spheres has been compared with those of nanoparticles and thin films. Chapter 4 contains the multiferroic properties of Bi4Ti3O12 nanoparticles. The chapter discusses how a ferroelectric material can be made multiferroic by decreasing the size in nano range. Chapter 5 presents the magnetic properties of CaF2 nanoparticles. Ferromagnetic properties of CaF2 nanoparticles prepared by two different methods have been compared. Miscellaneous section describes the artefacts related to negative magnetization observed under zero field cooled conditions and the ways they can be avoided in the context of CoCr2O4. Negative magnetization in CoCr2-xFexO4 (0 ≤ x ≥ 1) has been shown to due to negative trapped field in the sample space of superconducting magnet.