Investigation of room temperature magnetic ordering in defect engineered tio2 based diluted magnetic oxide semiconductors

Abstract

quotSpintronicsquot is a developing technology in which spin degree of freedom and their charge transport are controlled by external magnetic/electrical fields. Efficient spin injection, spin transfer and spin detection are the key parameters in spintronic devices. Resistance mismatch at semiconductor-ferromagnetic metal interfaces are usually not purely Ohmic, which restricts the efficient spin injection and transport. To overcome this contact problem, intense research is currently ongoing globally for developing Diluted Magnetic Semiconductor (DMS) and Diluted Magnetic Oxide Semiconductor (DMO) as it exhibits ferromagnetic property. Mostly, transition metal doped wide band gap metal oxides, such as TiO2, ZnO have been used as DMOs. In such DMOs, impurity band and dimensionality plays a crucial role in spin and electron transport properties of the material but bulk production of these DMOs are still a challenging task. However, though there are many reports exist in literature on TiO2-based DMS, there is no clear evidence about the origin of the room temperature ferromagnetism. Some reports suggest the formation of magnetic metal clusters as the origin of ferromagnetic signal, while most of the recent literatures strongly suggest that the ferromagnetic ordering could be mediated by carriers or defects. Yet, ambiguous explanation about the role of defects on observed ferromagnetism in DMOs is remaining as an unsolved problem.In this investigation, in order to comprehend the vital role of defects on the magnetic ordering in TiO2 based DMOs, disorders were introduced along with transition metal (TM) and rare-earth element (RE) dopants using controlled atmosphere rapid cooling process (i.e. analyte has to be rapidly cooled down to 83K from 673K). The TM and RE elements have been doped in anatase TiO2 lattice based on their net magnetic moments newline