Experimental And Theoretical Studies Of Strongly Correlated Multiferroic Oxides

Abstract

This thesis presents the synthesis and investigations of physical and chemical properties of multiferroic materials experimentally as well as theoretically. Multiferroics are materials in which at least two of the three ferroic orders, ferroelectricity, ferromagnetism and ferroelasticity occur in the same phase. Multiferroics, have the potential to be used as a four state as well as cross switchable memory devices. The thesis is organized into seven Chapters.

Chapter 1 gives a brief overview of the different facets of multiferroics, explaining the origin of Multiferroicity and magnetoelectric coupling, their possible technological applications and the challenges involved.

Chapter 2-4 concerns the experimental aspects and chapter 5-7 concerns the theoretical aspects.

Chapter 2 deals with experimental investigations on nanoscale charge-ordered rare earth manganites. It shows with decreasing particle size the ferromagnetic interaction increases and the charge-ordering vanishes down to the lowest sizes.

Chapter 3 describes magneto-dielectric, magnetic and ferroelectric properties of hexagonal LuMnO3. It also describes the Raman spectroscopy of this compound through the magnetic and ferroelectric transition temperatures.

Chapter 4 deals with the anisotropic multiferroic properties in single crystals of hexagonal ErMnO3.

In chapter 5 a brief introduction of density functional theory (DFT) is given.

Chapter 6 deals with the magneto-structural changes, spin-phonon couplings and crystal field splittings for the different magnetic orderings LuMnO3.

Chapter 7 elucidates the role of Lu d0-ness for the ferroelectricity observed of this compound.