I. Abu-Aljarayesh

Transmission of a Gaussian beam through a Fabry–Perot interferometer

The transmission of a Gaussian beam through a Fabry-Perot interferometer (FPI) has been investigated. The equation for the electric field of the transmitted beam was derived and then the transmitted irradiance I(t) was numerically calculated for different selected parameters of both the FPI and the beam. The results show that the energy profile of the transmitted beam has been distorted to different degrees depending on the various parameters of the Gaussian beam and the FPI. Moreover the results show that the positions of the peaks of the transmitted beam are shifted, especially for intermediate waists for which the arctan term is nonlinear. The results also show that for nonnormal incidence successive transmitted beams are spatially separated and are not interfering appreciably with each other.

On the static and time-dependent magnetic properties of Fe3O4 fine particles: effect of oxidation

Abstract In this work, the results of static and time-dependent magnetization measurements on three systems of Fe 3 O 4 fine particles are reported. Measurements of the static magnetization were carried out in the temperature range 293 K ≤ T ≤ 423 K , and of the remanent magnetization in the temperature range 5 K ≤ T ≤ 300 K over the period of time 30 s ≤ t ≤ 300 s . The remanent magnetization was found to obey the relation M = C − S 1 n t . Annealing the sample at 250°C was found to increase its magnetic anisotropy constant. The results were analyzed within the context of Neels theory of magnetic clusters.

The temperature dependence of the optical anisotropy in magnetic fluids: birefringence and dichroism

Abstract The temperature dependence of birefringence, δ, and dichroism, Δ A , in Fe 3 O 4 Isopar-M based magnetic fluids have been investigated in the temperature range 100 T T s , and then both increase with temperature until they reach a maximum at a temperature T m , and then decrease with temperature for T > T m . The values of T m and T s are found to vary with concentration and the applied field. The results also show that δ- H 2 and Δ A-H 2 curves deviate from linearity. This deviation is attributed to interparticle interactions, the orientation of pre-existing clusters, and the field-induced chain formation.

Mössbauer and X-ray diffraction studies of heat-treated Fe3O4 fine particles

Abstract Samples of Fe3O4 fine particles heated at different temperatures have been studied using Mossbauer spectroscopy and X-ray diffraction. The fresh sample and that heated at 160°C both show superparamagnetic behavior. However, the Mossbauer spectra of samples heated at higher temperatures are all magnetically split. The Mossbauer data with and without the application of ∼ 0.4 T magnetic field perpendicular to the direction of propagation of the γ-rays indicate a gradual conversion of Fe3O4 to γ-Fe2O3 and then to α-Fe2O3 with increasing heating temperature, and a complete conversion to α-Fe2O3 in the sample heated at 550°C. The observed increase in the Bhf with heating temperature is attributed to particle growth. Also, X-ray data indicate particle growth with increasing heating temperature, and partial transformation to α-Fe2O3 in the sample heated at 350°C, and a total conversion in the sample heated at 550°C.

On the concentration dependence of Faraday rotation in magnetic fluids

Faraday rotation and magnetization measurements at room temperature were undertaken on Fe/sub 3/O/sub 4/ particle magnetic fluids with different concentrations. The results show that Faraday rotation follows a Langevin-type behavior with the applied magnetic field. The results also show that Faraday rotation increases with the concentration of the sample and tends to saturate at higher fields for higher concentration. By comparing the optical and magnetic data the role of chain formation in Faraday rotation is discussed. From these measurements, the chain length at given field is found to be linear with the concentration of the sample, a result that is in agreement with recent studies on the concentration dependence of chain formation. >

Magneto-dielectric anisotropy in magnetic fluids determined from magneto-optical measurements

Abstract Magneto-optical measurements on magnetic fluids have been utilized to determine the magneto-dielectric anisotropy effect in magnetic fluids. Our results show that the dielectric constant, e| ∗ , seen by light polarized in the direction of the applied magnetic field increases with the field, while e ⊥ ∗ seen by light polarized normal to the field decreases with the field. Moreover, the results also show that e | ∗ exhibits a peak with temperature while e ⊥ ∗ exhibits a minimum. Our calculated results are in good agreement with those obtained using conventional impedance measurement techniques, with the advantage that this method is not affected by the electrode effect, parasitic impedances, skin depth and accuracy-related problems that are typical of conventional impedance measurement techniques.

Oxidation state of the upper mantle beneath the northwestern part of the Arabian lithosphere

Abstract The Fe3+ contents of spinels from upper mantle lherzolite xenoliths occurring in the Pleistocene alkali basalts of northeast Jordan have been determined using 57Fe Mossbauer spectroscopy at room temperature. The determined Fe3+ fractions were used to calculate oxygen fugacity. The calculated ƒ O 2 -T-P conditions are consistent with derivation of the lherzolite samples from a relatively oxidized source region dominated by CO2 and/or H2O fluid species. Calculated ƒ O 2 s range from 0.5 above to 1.1 log-units below the fayalite-magnetite-quartz (FMQ) buffer. Estimated Fe 3+ Fe total - ratios from microprobe analyses are 2–7% more than those determined from Mossbauer spectroscopy and can shift the computed oxygen fugacity by 0.1 to 0.6 log-units. Pressure and/or temperature does not contribute significantly in the calculated Δƒ O 2 . The average Δƒ O 2 (relative to FMQ) is −0.29 ± 0.4 log-units. This is higher than that reported for western Europe (−0.89 ± 0.58), British Columbia (−1.05 ± 0.3), and eastern Australia (−1.78 ± 0.66).

Carrier and chain formation dependence of birefringence in magnetic fluids

Abstract Measurements of the birefringence in Fe 3 O 4 magnetic fluids were undertaken in the temperature range 190–313 K in magnetic fields up to 0.7 kOe. Our results show that the birefringence increases with temperature exhibiting a maximum near the melting point, T m , of the liquid carrier (kerosene, decalin and Isopar M). For T > T m the birefringence follows a generalized Curie-Weiss law yielding positive ordering temperatures for the three samples. Moreover, our results show that the birefringence behaves irreversibly with temperature, in the decalin based sample. The results also show that the magnitude of the birefringence and the shape of the maximum change with the applied magnetic fields.

Temperature dependence of the Faraday rotation and the transmission of light in magnetic fluids

Abstract Measurements of the Faraday rotation and transmission of light in Fe 3 O 4 particle magnetic fluid were undertaken in the temperature range 100–325 K. Our results show that both the transmission and Faraday rotation exhibit a cusp at 225 K. For T T > 225 K following a generalized Curie-Weiss type behaviour.

Thermodynamic assessment in heavy metal migration at El-Akader landfill site, North Jordan.

Thermodynamic analysis of subsoil pore water indicates that Fe, Cu, Zn, and Pb exist as a metal hydroxy complex of the forms [Me OH] + and [Me(OH2)]o, although a complex of [PbCl]+ is also significant, but not predominant. The analysis also demonstrates that the dissolved transition metal concentration of the subsoil pore waters are controlled at carbonate minerals saturation levels, whereas Fe concentration in leachate solutions associated with waters are controlled at FeS2 saturation levels. Thermodynamic calculations and Eh-pH diagrams suggest that Fe(OH)2, Zn(OH)2 and Pb(OH)2 are not stable phases in the solids of the subsoil.