Search

In this work, we have grown nanostructured vanadium dioxide (VO2) thin films by a spray pyrolysis coating method on glass pre-heated substrates at 450 °C and studied their optical and electronic properties. As-prepared film structure and morphology, with a thickness of ~ 400 nm, were examined by X-ray diffraction, Raman spectra, and atomic force microscopy (AFM), thus revealing a polycrystalline monoclinic M1 phase. On the other hand, the electrical resistance was measured as a function of the temperature in the range of 25 to 100 °C where a clear transition from the M1 phase at T = 25 °C to the metallic one (conductive phase) at ~ 60 °C was observed. This also confirms the stability of the M1 phase for T < 60 °C. The electronic properties and band structure were additionally investigated by the local density approximation (LDA) using the first principle of the Korringa-Kohn-Rostroker (KKR). As a result, our material showed a magnetic property, specifically an antiferromagnetic stabilization of the M1 phase. [ABSTRACT FROM AUTHOR]

We have investigated in this work the physical, optical, electronic, and the magnetic behavior (Curie temperature, magnetic moment) of Zn.1-x.MxO (M = Fe 5%, Co 1%, Cr 5%, and Mn 5%), diluted magnetic semiconductors (DMSs). The samples were deposited on glass substrate by the spray pyrolysis technique, and the results of the x-ray diffraction (XRD) of the prepared substrates was used to prove the incorporation of the dopants into the ZnO lattice host; the ferromagnetic and the antiferromagnetic state competitions and their effects on the physical, magnetic, and optical properties, were investigated. The electronic structure and magnetic properties of transition metal (TM) defects, were investigated in detail, by using the Korringa-Kohn-Rostoker (KKR) method combined with the coherent potential approximation (CPA). As a result, doping by TM impurities induce the ferromagnetism with different competitions between the ferromagnetic and antiferromagnetic states, which affects the physical properties of the TM (Fe, Fe/Co, Cr, and Mn)-doped ZnO, with a Curie temperature closer to room-temperature ferromagnetic. [ABSTRACT FROM AUTHOR]

The purpose of our study is to find a suitable material to be used in spintronic applications and to find the relation between the parameters of deposition by spray pyrolysis technic (temperature, concentration of Ni doping) and the ferromagnetic properties (Curie temperature, magnetic moment). The nickel-doped zinc oxide, Zn.1− x.Ni xO ( x = 0.01, 0.03, 0.05), and diluted magnetic semiconductors (DMSs) are synthesized by the spray pyrolysis technic. The results of The X-ray diffraction (XRD) of prepared substrates confirm the incorporation of the dopants into the ZnO lattice structure. The spin-polarized electronic properties has been found and was investigated in detail by using the density-functional theory (DFT), the local density approximation (LDA), and The Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA). As result, nickel doping brings up a half-metallic appearance due to the hybridization between the 3d state of Nickel impurities and the oxygen 2p state. The mechanism of the interatomic exchange has been explained as being a p-d double exchange. [ABSTRACT FROM AUTHOR]