Studies on Multifunction Oxides for Development of Memory Devices

Investigations and usefulness of various multifunctional oxides, such as, multiferroics, ferroelectrics, diluted magnetic semiconductors, mixed valent manganites etc, in new functional devices having high performance logic and non-volatile memory storage applications, is a topic of current research interest. Mutiferriocs, form the facinating class of multifunctional materials which exhibit two or more coupled ferroic orders. Their incorporation for spintronic application gives the advantage of, use of two functionalites, such as, ferromagnetism and ferroelectricity and raises possibility of new functionalities due to coupling between two orderings. On the other hand, semiconductor based spintronic materials are very important due to the fact that, only magnetic materials can not amplify the signal while semiconductor based spintronic devices provide amplification as well as act as a multi-functional devices. Use of ferromagnetic semiconductors, where, low concentration of magnetic ions is incorporated into semiconductor host lattices (e.g. DMS), can fulfill this requirement which utilizes spin degree of freedom in conventional charge based electronics.

Amongst various multiferroic materials, BiFeO3 (BFO) acquire unique place because of the coexistence of ferroelectricity and antiferromagnetism at room temperature. In this presentation, I will show the results of studies on the improvement in the electrical and magnetic properties of Ba doped BFO (Bi1-xBaxFeO3; x = 0.0, 0.05,…0.20) films in the context of variation in Ba doping concentration and film thickness. Part of talk will be devoted to the electronic structure studies on pure and doped ZnO samples. Using Valence Band Spectroscopy (VBS) and Resonant Photoemission Spectroscopy (RPES) measurements, modifications in the electronic structure of Co-doped ZnO will be discussed in detail in the context of increment in the occupation of Co-3d states with Co-content extends the VB maxima edge.