Cr doping leads to narrowing of the band gap and formation of isolated BMPs.

Origin of unexpected defect engineered room-temperature ferromagnetism observed in tin-doped indium oxide (ITO) nanostructures (Nanowires, Nano-combs) and nanocrystalline thin films fabricated by pulsed laser deposition has been investigated. It is found that the ITO nanostructures prepared under argon environment exhibit strongest ferromagnetic signature as compared to that nanocrystalline thin films grown at oxygen. The evidence of singly ionized oxygen vacancy (V0+) defects, obtained from various spectroscopic measurements, suggests that such V0+ defects are mainly responsible for the intrinsic ferromagnetic ordering. The exchange interaction of the defects provides extensive opportunity to tune the room-temperature d0 ferromagnetism and optical properties of ITOs.

The magnetic behavior of TiO 2 and doped TiO 2 nanocrystals has been a challenge due to the unambiguous nature of defects present in oxide semiconductors. Here, a simple, low-temperature sol−gel method is developed for the synthesis of low-dimensional and highly efficient stable anatase TiO 2 nanocrystals. The X-ray powder diffraction pattern and Raman spectra confirm the formation of a single-phase anatase structure of TiO 2 . High-resolution transmission electron microscopy studies reveal the crystalline nature of the sol−gel-derived nanocrystals. The increase in lattice parameters together with the shifting and broadening of the most intense E g (1) mode in micro-Raman spectra of Codoped TiO 2 nanocrystals indicate the incorporation of Co in TiO 2 . Shifting of the absorption edge to the visible region in UV−visible spectra indicates narrowing of the band gap due to Co incorporation in TiO 2 . X-ray photoelectron spectra confirm the presence of Co 2+ and Co 3+ in Co-doped TiO 2 samples. Oxygen vacancy defects lead to the formation of bound magnetic polarons which induces a weak ferromagnetic behavior in air-annealed 3% Co-doped TiO 2 at room temperature. It is observed that irrespective of the dopant ion, whether magnetic or nonmagnetic, the overlapping of bound magnetic polarons alone can induce ferromagnetism, while the magnetic impurities give rise to an enhanced paramagnetic moment for higher Co concentrations. A detailed understanding on the variation of these magnetic properties by estimating the concentration of bound magnetic polarons is presented, which is in corroboration with the photoluminescence studies. The observed band-gap narrowing in Co-doped TiO 2 nanostructures and the mechanism underlying the magnetic interactions associated with the magnetic impurity concentration are advantageous from an applied perspective, especially in the field of spintronic and magneto-optic devices.

The nature of BMPs, whether overlapped or isolated, determines the magnetic behavior of Fe-doped TiO2.

No abstract

Oxide based dilute magnetic semiconductor materials are of great interest and this study focusses on the optical and magnetic behavior of non-magnetic element doped TiO2 nanocrystals which provides a significant reduction in bandgap with enhanced magnetization.

Defect engineering of Ni-doped TiO2 could tailor the magnetic properties through BMP interactions, which is advantageous for spintronics applications.

High pressure Raman spectroscopy, X-ray diffraction, and dielectric measurements have been carried out in Ba1−xSrxTiO3 (x = 0.05 and 0.1). Detailed structural analysis revealed a single phase transition from tetragonal P4mm to cubic Pm3m symmetry. Increase in Sr ion concentration resulted in decrease in the phase transition pressure. The dielectric measurements showed considerable lowering of transition pressure which has been attributed to bulk behaviour of the material.