Safia Anjum

Role of vacancies in transport and magnetic properties of nickel ferrite thin films

Nickel ferrite thin films were synthesized by pulsed laser deposition. It was determined that the monotonic increase in saturation magnetization and the non-monotonic increase in electrical conductivity depend on the oxygen partial pressure during the growth of the thin films. A substantial reduction in magnetization was found which ranged between 0.4% and 40% of the bulk value as the oxygen partial pressure increased from 0.2 × 10−6 Torr to 500 mTorr during the deposition of the films. There was a three orders of magnitude increase in conductivity for the sample prepared under the most oxygen deficient environment (partial pressure of oxygen 0.2 × 10−6 Torr). These variations in saturation magnetization and conductivity are described within the framework of cation/oxygen vacancies in an inverse spinel nickel ferrite structure. The changes in the electronic structure due to the presence of the vacancies were investigated using x-ray photoelectron spectroscopy, which confirmed the formation of lower valent Ni for the samples prepared in an oxygen deficient atmosphere.

Effect of Cu-Doped Nickel Ferrites on Structural, Magnetic, and Dielectric Properties

NiCu ferrites with the general formula Ni1-xCuxFe2O4, where x=0, 0.2, 0.4, 0.6, 0.8 have been synthesized by double sintering method. The single- phase spinel structure is confirmed by X-ray Diffractometer. This analysis showed the increasing behavior of lattice parameter due to the larger ionic radii of the Cu ion. Fourier transform infrared spectra confirmed the two prominent bands of spinel ferrites in the range (1000-400) cm-1. Magnetic properties are studied using Vibrating Sample Magnetometer. It is investigated that the saturation magnetization decreases linearly as the copper concentration increases. The surface morphology is carried out using Scanning Electron Microscopy. The dielectric properties have been investigated as a function of frequency. The dielectric constant is decreased and AC conductivity is increased at higher frequency.

Effects of Cr and Fe co-doping on structural, optical, electrical and magnetic properties of titanium dioxide (TiO2)

Abstract A series of Ti0.9Fe0.1-xCrxO2 (where x = 0.0, 0.02, 0.04, 0.6, 0.08, 0.10) was synthesized using the powder metallurgy route. The structural, morphological, magnetic, optical and electrical properties were investigated by X-ray diffractometry (XRD), Raman spectroscopy, scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), UV-Vis spectroscopy and four probe technique, respectively. The rutile phase was confirmed by XRD analysis which was also verified by Raman spectroscopy. It was observed that the grain size increased as the concentration of Cr increased. M-H loops extracted from VSM analysis revealed anti-ferromagnetic, weak ferromagnetic and paramagnetic behaviors at room temperature. The band gap energy and resistivity measurements exhibited the semiconducting nature of Ti0.9Fe0.1-xCrxO2 based diluted magnetic semiconductors.

Optical emission spectroscopy of magnetically confined laser induced vanadium pentoxide (V2O5) plasma

Optical emission spectra of a laser induced plasma of vanadium pentoxide (V2O5) using a Nd:YAG laser (1064 nm, 10 ns) in the presence and absence of the magnetic field of 0.45 T have been investigated. The effect of the magnetic field (B) on the V2O5 plasma at various laser irradiances ranging from 0.64 GW cm−2 to 2.56 GW cm−2 is investigated while keeping the pressure of environmental gases of Ar and Ne constant at 100 Torr. The magnetic field effect on plasma parameters of V2O5 is also explored at different delay times ranging from 0 μs to 10 μs for both environmental gases of Ar and Ne at the laser irradiance of 1.28 GW cm−2. It is revealed that both the emission intensity and electron temperature of the vanadium pentoxide plasma initially increase with increasing irradiance due to the enhanced energy deposition and mass ablation rate. After achieving a certain maximum, both exhibit a decreasing trend or saturation which is attributable to the plasma shielding effect. However, the electron density shows a decreasing trend with increasing laser irradiance. This trend remains the same for both cases, i.e., in the presence and in the absence of magnetic field and for both background gases of Ar and Ne. However, it is revealed that both the electron temperature and electron density of the V2O5 plasma are significantly enhanced in the presence of the magnetic field for both environments at all laser irradiances and delay times, and more pronounced effects are observed at higher irradiances. The enhancement in plasma parameters is attributed to the confinement as well as Joule heating effects caused by magnetic field employment. The confinement of the plasma is also confirmed by the analytically calculated value of magnetic pressure β, which is smaller than plasma pressure at all irradiances and delay times, and therefore confirms the validity of magnetic confinement of the V2O5 plasma.Optical emission spectra of a laser induced plasma of vanadium pentoxide (V2O5) using a Nd:YAG laser (1064 nm, 10 ns) in the presence and absence of the magnetic field of 0.45 T have been investigated. The effect of the magnetic field (B) on the V2O5 plasma at various laser irradiances ranging from 0.64 GW cm−2 to 2.56 GW cm−2 is investigated while keeping the pressure of environmental gases of Ar and Ne constant at 100 Torr. The magnetic field effect on plasma parameters of V2O5 is also explored at different delay times ranging from 0 μs to 10 μs for both environmental gases of Ar and Ne at the laser irradiance of 1.28 GW cm−2. It is revealed that both the emission intensity and electron temperature of the vanadium pentoxide plasma initially increase with increasing irradiance due to the enhanced energy deposition and mass ablation rate. After achieving a certain maximum, both exhibit a decreasing trend or saturation which is attributable to the plasma shielding effect. However, the electron density show...

Investigation of Structural, Magnetic, and Optical Properties of ZnO Codoped with Co and Cd

Co and Cd have been codoped in ZnO using a simple solid state reaction technique to synthesize dilute magnetic oxide semiconductors of composition Zn0.9Co0.1−xCdxO ( with an increment of 0.02). Hexagonal wurtzite structure has been obtained for samples up to , using X-ray diffractometry. However, at and 0.1, secondary peak of CdO is observed. Raman spectra of the samples have been obtained in 200–800 cm−1 range. UV-VIS spectrophotometer is used to study the optical properties, which shows that band gap energy decreases with the increase in Cd concentration. A weak ferromagnetic behavior was evident which decreased further by adding Cd in the series. Room temperature resistivity measurements performed using four-point probe technique showed that their values lie in the semiconductor range. Structural morphology of the samples has been investigated by a scanning electron microscope and grain size has been determined. Raman spectra and Fourier transform infrared spectroscopy revealed the successful incorporation of Co and Cd ions into the host ZnO lattice.

Synthesis, characterization of CaF2 doped silicate glass-ceramics

This paper reports the fabrication and characterization of silicate glass-ceramics doped with (0-12mol%) CaF2. TGA-DSC analysis was carried out to determine the crystallization temperature and stability of glass measured by two glass parameters; Hruby parameter KH=(Tx-Tg)/(TL-Tx) and Weinberg parameter KW=(Tc-Tg)/TL. It was found that with CaF2 doping improved sinterability at low temperature and provided stability to the glass. The XRD pattern exhibits a single phase of combeite and doping of CaF2 cause increase in crystallite size. Microstructure of samples was also improved with CaF2 addition, pores were significantly reduced. After 15days immersion in simulated body fluid all samples developed apatite layer onto its surface. Hence, the addition of CaF2 provided bioactive glass-ceramic material having a low processing temperature.

Substitutional effect of copper on the cation distribution in cobalt chromium ferrites and their structural and magnetic properties

Abstract A series of copper substituted cobalt chromium ferrites, CuxCo1 - xCr0.5Fe1.5O4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) has been synthesized, by employing powder metallurgy method. Calcination of the samples has been carried out for 24 hours at 1100 °C. The resultant materials have been investigated by using a variety of techniques, including X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM)), scanning electron microscopy (SEM), and ultraviolet visible spectroscopy (UV-Vis). The XRD patterns confirmed that all compositions had a cubic spinel structure with a single phase and the lattice parameter was found to increase with increasing copper concentration. FT-IR spectroscopy has been used for studying the chemical bonds in the spinel ferrite. Shifting of the bands ν1 and ν2 has been observed. It has been revealed from VSM analysis that saturation magnetization and coercivity decrease with rising the Cu+2 doping. Magnetic properties have been explained on the basis of cation distribution. Scanning electron microscopy (SEM) has been used to study the surface morphology of prepared samples. UV-Vis analysis revealed the optical absorption of the samples. An increase in band gaps has been observed with increasing copper concentration in the sample.

Surface modification of platinum by laser-produced X-rays

Laser-induced plasma is used as an X-ray source for the growth of hillocks like nanostructures on platinum surface. To generate X-rays, plasma is produced by Nd:YAG laser, which is operated at second harmonics (λ = 532 nm, E = 400 mJ). Analytical grade 5 N pure Al, Cu and W are used as laser targets for X-rays production. X-rays produced from Al, Cu and W plasmas are used to irradiate three analytical grade (5 N pure) platinum substrates, respectively, under the vacuum ∼10−4 torr. XRD analysis shows considerable structural changes in the exposed platinum. The decrement in reflection intensities, increment in dislocation line density, change in d-spacing and disturbance in the periodicity of planes evidently prove these structural changes. Atomic force microscope AFM topographic analysis of the platinum exposed to X-rays emitted from Al, Cu and W targets showed that nanometer-size hillocks are produced on the platinum surface irrespective of the source. It has also been observed that due to these hillocks, the roughness of the surface has increased. Conductivity of hillocks produced from X-rays produced by Al, Cu and W targets is compared and it is shown that the hillocks produced by Al target X-rays have better conductivity compared to the hillocks produced by X-rays from Cu and W targets.