International Journal of Physics | Vol. 2, No. 5, May 2011 | pp. 35–42
DOI: 10.46882/2011/IJP/000017
Article Type: Original Research Paper
Title: Microstructural and Magnetic Modifications of Iron Oxide Thin Films Fabricated via Pulsed Laser Deposition
Names of Authors: S. O. Adebayo¹, R. J. Green²
Authors’ Affiliations: ¹Department of Physics, Landmark University, Omu-Aran, Nigeria; ²Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, UK
Abstract: Epitaxial iron oxide thin films, particularly magnetite (Fe₃O₄) and maghemite (gamma-Fe₂O₃), are highly attractive for high-density magnetic recording media and spintronic devices due to their high Curie temperatures and high spin polarization. This paper details the structural and magnetic variations observed in iron oxide thin films grown on magnesium oxide (MgO) substrates via pulsed laser deposition (PLD). The growth parameters, including oxygen background pressure (10⁻⁵ Pa to 10 Pa) and substrate temperature (500 K to 850 K), were varied systematically to alter the iron oxidation states. X-ray diffraction and high-resolution transmission electron microscopy confirmed the growth of single-phase Fe₃O₄ thin films with a cubic inverse spinel structure under an optimal pressure of 10⁻³ Pa. Vibrating sample magnetometry (VSM) revealed a saturation magnetization of 410 emu/cm³ at room temperature, which approaches the bulk value. We observed a clear Verwey transition at 120 K in electrical resistivity plots, which served as a sensitive indicator of oxygen stoichiometry. Films grown at higher oxygen pressures transitioned into the alpha-Fe₂O₃ phase, showing an abrupt drop in magnetic remanence. These results demonstrate that adjusting the PLD ambient environment allows precise phase control for magnetic thin-film optimization.
Keywords: Pulsed laser deposition; Iron oxide thin films; Magnetite; Saturation magnetization; Verwey transition; X-ray diffraction; Inverse spinel structure; Spintronics.
Manuscript Timeline: Received: February 15, 2011; Revised: March 24, 2011; Accepted: April 18, 2011; Published: May 11, 2011.
Citation: Adebayo, S. O., & Green, R. J. (2011). Microstructural and Magnetic Modifications of Iron Oxide Thin Films Fabricated via Pulsed Laser Deposition. International Journal of Physics, 2(5), 35–42.
International Journal of Physics | Vol. 2, No. 6, June 2011 | pp. 43–51
DOI: 10.46882/2011/IJP/000018
Article Type: Original Research Paper
Title: Theoretical Exploration of Non-Linear Optical Properties in Organic Dye Derivatives Using Density Functional Theory
Names of Authors: Y. A. Bello¹, H. M. Al-Qahtani²
Authors’ Affiliations: ¹Department of Physics, University of Ilorin, Ilorin, Nigeria; ²Department of Physics, King Saud University, Riyadh, Saudi Arabia
Abstract: Organic molecules featuring strong donor-acceptor configurations exhibit large non-linear optical (NLO) responses, making them ideal for high-speed electro-optic modulators and optical switches. This paper provides a theoretical investigation into the electronic configurations, frontier molecular orbital gap, and non-linear optical parameters of a series of novel azobenzene dye derivatives. The quantum chemical computations were executed using density functional theory (DFT) at the B3LYP/6-311G(d,p) level. The electric dipole moment, molecular polarizability, and first-order hyperpolarizability (beta) were computed for each derivative. Our results indicate that introducing strong electron-withdrawing nitro (-NO₂) and cyano (-CN) groups at the para-position narrows the HOMO-LUMO energy gap from 3.42 eV to 2.15 eV. This modification accelerates internal charge transfer across the conjugated pi-linker system. Consequently, the calculated first-order hyperpolarizability of the nitro-substituted derivative reached 4.5 x 10⁻³⁰ esu, which is approximately 25 times larger than that of standard urea references. The frequency-dependent NLO responses were also modeled, highlighting strong dispersion effects near resonance frequencies. These quantitative variations indicate that optimizing substituent electron affinities can enhance the efficiency of organic non-linear optical devices.
Keywords: Non-linear optics; Density functional theory; Azobenzene dyes; Hyperpolarizability; HOMO-LUMO gap; Charge transfer; Quantum chemical calculation; Electro-optic modulator.
Manuscript Timeline: Received: March 20, 2011; Revised: April 28, 2011; Accepted: May 20, 2011; Published: June 15, 2011.
Citation: Bello, Y. A., & Al-Qahtani, H. M. (2011). Theoretical Exploration of Non-Linear Optical Properties in Organic Dye Derivatives Using Density Functional Theory. International Journal of Physics, 2(6), 43–51.
International Journal of Physics | Vol. 2, No. 12, December 2011 | pp. 92–100
DOI: 10.46882/2011/IJP/000024
Article Type: Original Research Paper
Title: Gravity Anomalies and Structural Interpretation of the Benue Trough Basins Using High-Resolution Satellite GOCE Data
Names of Authors: M. N. Obi¹, H. J. Fischer²
Authors’ Affiliations: ¹Department of Physics and Astronomy, University of Nigeria, Nsukka, Nigeria; ²Department of Geosciences, University of Kiel, Kiel, Germany
Abstract: The Benue Trough of Nigeria is a major geological structure whose tectonic evolution and sedimentary thickness are critical for regional mineral and hydrocarbon prospecting. This study presents a structural interpretation of the Upper Benue Trough using high-resolution gravity field gradients gathered by the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite. The raw gravity markers were processed to generate Bouguer and residual gravity anomaly maps of the basin. Forward and inverse modeling configurations were executed along three transverse profiles to estimate the basement depth and trace hidden fault networks. The Bouguer anomaly values ranged from -45 mGal to +25 mGal, outlining a series of prominent sub-basins. Our structural models indicate that the sedimentary thickness peaks at 5.8 km within the Lau Basin, decreasing towards the structural flanks. The residual gravity field highlighted a network of parallel lineaments oriented in an NE-SW direction, consistent with a strike-slip tectonic origin. Spectral analysis confirmed a two-tier depth model, with deep crustal anomalies seated around 18 km and shallower volcanic intrusions at 2.4 km. This satellite-derived structural frame enhances our understanding of rift dynamics across West Africa.
Keywords: Gravity anomalies; Benue Trough; GOCE satellite; Bouguer anomaly; Sedimentary basin; Structural modeling; Tectonic lineaments; Hydrocarbon exploration.
Manuscript Timeline: Received: September 12, 2011; Revised: October 24, 2011; Accepted: November 18, 2011; Published: December 11, 2011.
Citation: Obi, M. N., & Fischer, H. J. (2011). Gravity Anomalies and Structural Interpretation of the Benue Trough Basins Using High-Resolution Satellite GOCE Data. International Journal of Physics, 2(12), 92–100.
International Journal of Physics | Vol. 2, No. 10, October 2011 | pp. 76–83
DOI: 10.46882/2011/IJP/000022
Article Type: Original Research Paper
Title: Soliton Solutions and Pulse Compression Dynamics in Highly Non-Linear Photonic Crystal Fibers
Names of Authors: A. E. Egbe¹, J. M. Harrison²
Authors’ Affiliations: ¹Department of Physics, University of Uyo, Uyo, Nigeria; ²School of Physics and Astronomy, University of Southampton, Southampton, UK
Abstract: Photonic crystal fibers (PCFs) offer unprecedented control over chromatic dispersion and non-linear optical interactions, making them ideal media for generating ultra-short optical pulses and supercontinuum fields. This paper presents an analytical and numerical investigation into the propagation of higher-order optical solitons and adiabatic pulse compression within a tailored silica PCF. The pulse dynamics are modeled by solving the generalized non-linear Schrodinger equation (GNLSE) using the split-step Fourier method. The simulation tracks 100-femtosecond pulses at a central operating wavelength of 1550 nm propagating through a fiber with a zero-dispersion wavelength designed at 1420 nm. Our numerical results show that tailoring the air-hole diameter over a fiber length of 2.5 meters triggers clean compression, reducing the pulse duration from 100 fs to a compressed minimum of 12 fs. This compression is accompanied by a twelve-fold increase in peak optical power without generating significant pedestal noise. We evaluate the disruptive impacts of higher-order Raman scattering and self-steepening, which induce a soliton self-frequency shift of 45 nm. These findings offer practical design equations for developing compact, fiber-based femtosecond laser sources for multi-photon biological imaging applications.
Keywords: Photonic crystal fibers; Optical solitons; Pulse compression; Non-linear Schrodinger equation; Split-step Fourier method; Raman scattering; Soliton self-frequency shift; Femtosecond lasers.
Manuscript Timeline: Received: July 08, 2011; Revised: August 19, 2011; Accepted: September 12, 2011; Published: October 03, 2011.
Citation: Egbe, A. E., & Harrison, J. M. (2011). Soliton Solutions and Pulse Compression Dynamics in Highly Non-Linear Photonic Crystal Fibers. International Journal of Physics, 2(10), 76–83.
International Journal of Physics | Vol. 2, No. 4, April 2011 | pp. 26–34
DOI: 10.46882/2011/IJP/000016
Article Type: Review Paper
Title: Progress in Metamaterial Cloaking Mechanisms: From Transformation Optics to Plasmonic Cloaks
Names of Authors: L. A. Cooper¹, A. O. Babalola²
Authors’ Affiliations: ¹Department of Electrical and Electronic Engineering, Imperial College London, London, UK; ²Department of Physics, Federal University of Technology, Akure, Nigeria
Abstract: Electromagnetic metamaterials have revolutionized the field of optics by enabling unusual material responses, such as negative refractive indices and artificial anisotropy. This review provides an analytical overview of the primary cloaking strategies developed over the past decade to render objects undetectable to incident radiation fields. We contrast the foundational framework of transformation optics, which routes electromagnetic fields around a hidden volume via spatially varying permittivity and permeability profiles, with alternative approaches including scattering cancellation and plasmonic cloaking. The technical challenges of implementing these models in experimental configurations are discussed, focusing on the trade-offs between operational bandwidth, structural loss, and device dimensions. While transformation-based cloaks are fundamentally constrained by causality to narrow operating frequencies, scattering cancellation systems offer a broader operational band for sub-wavelength objects. We examine recent advances in coordinate transformation equations that reduce the necessity for extreme, non-local material parameters, making fabrication via standard lithographic methods more achievable. The review concludes by highlighting the emerging application of metasurfaces for planar, low-profile illusion optics and skin cloaks operating across visible light frequencies.
Keywords: Electromagnetic metamaterials; Transformation optics; Cloaking mechanisms; Scattering cancellation; Plasmonic structures; Refractive index; Spatial permittivity; Metasurfaces.
Manuscript Timeline: Received: January 10, 2011; Revised: February 22, 2011; Accepted: March 14, 2011; Published: April 05, 2011.
Citation: Cooper, L. A., & Babalola, A. O. (2011). Progress in Metamaterial Cloaking Mechanisms: From Transformation Optics to Plasmonic Cloaks. International Journal of Physics, 2(4), 26–34.
International Journal of Physics | Vol. 2, No. 3, March 2011 | pp. 18–25
DOI: 10.46882/2011/IJP/000015
Article Type: Original Research Paper
Title: Assessment of Natural Radioactivity Levels and Radiation Hazards in Soil Profiles of Coal Mining Areas in Enugu, Nigeria
Names of Authors: J. C. Nwachukwu¹, M. S. Al-Hassan²
Authors’ Affiliations: ¹Department of Physics, University of Nigeria, Nsukka, Nigeria; ²Department of Physics, Ahmadu Bello University, Zaria, Nigeria
Abstract: Mining activities often elevate environmental radiation levels by bringing naturally occurring radioactive materials (NORM) to the surface, posing potential health hazards to surrounding populations. This study evaluates the activity concentrations of primordial radionuclides Uranium-238, Thorium-232, and Potassium-40 in soil profiles collected around historical coal mining fields in Enugu, Nigeria. A high-purity germanium (HPGe) gamma-ray spectrometer was utilized to analyze 50 topsoil and core soil samples. The mean activity concentrations were determined to be 28.4 ± 4.2 Bq/kg for Uranium-238, 42.1 ± 5.6 Bq/kg for Thorium-232, and 315.8 ± 24.1 Bq/kg for Potassium-40. These baseline radio-analytical data were utilized to calculate standard radiological hazard parameters, including the radium equivalent activity (Ra_eq), the external hazard index (H_ex), and the absorbed gamma dose rate in the air. The mean radium equivalent activity was 112.9 Bq/kg, which falls well below the internationally recommended safety limit of 370 Bq/kg. The corresponding annual effective dose equivalent received by the local population was estimated at 0.07 mSv, confirming that the radiation risk remains within safe operational limits. These evaluations provide an essential environmental reference frame for future radiological monitoring programs in the region.
Keywords: Gamma spectrometry; Natural radioactivity; Coal mining; Radiological hazards; Radium equivalent activity; Absorbed dose rate; Environmental monitoring; Soil profiles.
Manuscript Timeline: Received: December 01, 2010; Revised: January 18, 2011; Accepted: February 09, 2011; Published: March 01, 2011.
Citation: Nwachukwu, J. C., & Al-Hassan, M. S. (2011). Assessment of Natural Radioactivity Levels and Radiation Hazards in Soil Profiles of Coal Mining Areas in Enugu, Nigeria. International Journal of Physics, 2(3), 18–25.