Study of Single and Double Perovskite Manganites for Magnetic Refrigeration

Abstract

This thesis investigates the less explored single and double perovskite structured manganites for its use in magnetocaloric applications. The first part is associated with the single perovskites in the ABO3 form where the B-site is occupied by the manganite ion and the A-site by Lanthanide based rare earth ions such as Eu and La. And the second part is associated with the double perovskites in the A2BB O6 form where the B site takes in the magnetic ion Nickel and the A-site is occupied by rare earth ions such as Sm and Dy. At the initial step, the synthesis conditions were optimized to achieve the single phased materials and its crystallographic parameters were determined using the X-Ray diffractometer. The surface morphology and particle size has remarkable influence on the magnetocaloric effect, hence they were analysed using the Field Emission Scanning Electron Microscope and High Resolution Transmission Electron Microscope. Later, the magnetic characteristics are measured under various conditions as follows; (i) Isofield magnetic measurement at Zero Field cooled and Field cooled state while varying the applied temperature (ii) Isothermal magnetic measurement at various temperatures based on the magnetic transition temperature of the material newline