Investigation of polar and magnetic ordering in Transition Metal Oxide thin film heterostructures

Abstract

Oxides become an important group of quantum materials of interesting fundamental many body physics due to the presence of strongly correlated electronic and magnetic states. The hunch for developing new devices using the broad functionalities of Oxides has given the birth of new technical field called Oxide Electronics. Over past two decades research in oxide thin fi lms has been boosted due to the invention of new deposition techniques to make ultra thin single crystalline films with novel structure and functionality of the material that are inaccessible in it's bulk from with the help of reduced dimensionality and strain engineering with substrates. Designing novel polar and magnetic ordering in some new strain stabilized engineered oxide thin films as well as heterostructures is going to be the key focus of this thesis with a strong future perspective in quantum technology & device science. A variety of ferroelectric and ferromagnetic transition metal oxides (TMO) have been thoroughly explored in this thesis in terms of their thin fi lm growth as well as polar and magnetic properties. Firstly thin fi lm of arti ficial hexagonal phase of perovskite TbMnO3 has been grown and stabilized with the imposed strain of the substrate. The high ferro- electric transition temperature(Tc = 800 K) of this room temperature ferroelectrics has been investigated with temperature dependent Transmission Electron Microscopy, Raman spectroscopy and optical ellipsometry. Secondly thin film of monoclinic double perovskite Tb2CoMnO6 has been grown and it's detail dielectric and magnetic properties have been investigated. An interesting and novel ferroelectric relaxor glass phase has been observed in this ferromagnetic oxide along with a magneto-dielectric coupling (4%) at considerable high temperature. Third and most importantly a 3d-5d electronic system based perovskite ferroelectric-magnetic thin fi lm hetero-structure of BaTiO3/SrIrO3 has been grown and an enhanced magnetic ordering has been observed via interfacial coupling probed with depth dependent x-ray photoelectron spectroscopy. At the end as an Appendix we have explored the integration of a new 2 dimensional material Borocarbonitride (BCN) on ox- ide which is Al2O3. we have extensively studied the room temperature enhancement of magnetic ordering along with temperature and nitrogen dependent transport crossover in the thin fi lms.