Onyekachi Oparaku - Academia.edu (original) (raw)

Papers by Onyekachi Oparaku

Research paper thumbnail of Theoretical evaluation of the temperature dependence of magnetic anisotropy constants of Nd 2 Fe 14 B: Effects of exchange field and crystal field strength

Applied Physics Express, 2015

To identify the possible mechanism of coercivity (H c) degradation of Nd-Fe-B sintered magnets, w... more To identify the possible mechanism of coercivity (H c) degradation of Nd-Fe-B sintered magnets, we study the roles of the exchange field acting on the 4f electrons in Nd ions and theoretically investigate how the variation of the exchange field affects the values of the magnetic anisotropy constants K 1 and K 2. We find that, with decreasing exchange field strength, both values decrease as a result of the lower asphericity of the 4f electron cloud, indicating that the local anisotropy constants might become small around the grain boundaries where the exchange fields are decreased owing to the smaller coordination number. wave function of the 4f electrons, and N R is the density of RE ions. Note that the CEF parameter

Research paper thumbnail of Effect Temperature On Fluorine Doped Tin Oxide Via Spray Pyrolysis Technique

International Journal of Scientific & Engineering Research, 2019

s. The synthesis of fluorine doped tin oxide thin films were successfully deposited onto well cle... more s. The synthesis of fluorine doped tin oxide thin films were successfully deposited onto well cleared glass substrate by varying the deposition temperature. The XRD patterns of the films showed that the deposited films are polycrystalline in nature having the characteristic peaks of tetragonal structure of SnO2.The peaks observed are (110), (101), (200), (211) and the preferential growth along the (110) direction. The current versus voltage plots of the material deposited with 380 0 C, 390 0 C and 400 o C, which represent sample FT4-FT6 showed a non-linear plot. It was observed to be non Ohmic semiconducting material. It was also noticed that as the temperature of the depositing material increases the thickness of the films increases. The resistivity of the material deposited decreases as the temperature and thickness of the films increases. It was observed that as the optical absorbance and reflectance decreases the wavelength of the incident radiation increases and transmittance increases as the wavelength of the incident radiation increases. The films deposited at 380 0 C, 390 0 C and 400 o C recorded energy gap of 2.6eV-3.0eV.

Research paper thumbnail of Corrected Conference Paper

The Temperature dependence of semiconductor energy gap has been theoretically investigated using ... more The Temperature dependence of semiconductor energy gap has been theoretically investigated using the Varshni Model. This involved a theoretical simulation of variation in fundamental energy gaps for aluminum (Al), galium (Ga) and gallium arsenide (GaAs) using MATLAB programme at temperature ranges of 0-300 K. The result showed that, as temperature increased the top of the valence band and the bottom of the conduction band increased, while the energy band gap decreased.

Conference Presentations by Onyekachi Oparaku

Research paper thumbnail of Theoretical Evaluation of Temperature Dependence of Energy Gap for Aluminum, Gallium and Gallium Arsenide

The Temperature dependence of semiconductor energy gap has been theoretically investigated using ... more The Temperature dependence of semiconductor energy gap has been theoretically investigated using the
Varshni Model. This involved a theoretical simulation of variation in fundamental energy gaps for
aluminum (Al), galium (Ga) and gallium arsenide (GaAs) using MATLAB programme at temperature
ranges of 0-300 K. The result showed that, as temperature increased the top of the valence band and the
bottom of the conduction band increased, while the energy band gap decreased.

Research paper thumbnail of Theoretical evaluation of the temperature dependence of magnetic anisotropy constants of Nd 2 Fe 14 B: Effects of exchange field and crystal field strength

Applied Physics Express, 2015

To identify the possible mechanism of coercivity (H c) degradation of Nd-Fe-B sintered magnets, w... more To identify the possible mechanism of coercivity (H c) degradation of Nd-Fe-B sintered magnets, we study the roles of the exchange field acting on the 4f electrons in Nd ions and theoretically investigate how the variation of the exchange field affects the values of the magnetic anisotropy constants K 1 and K 2. We find that, with decreasing exchange field strength, both values decrease as a result of the lower asphericity of the 4f electron cloud, indicating that the local anisotropy constants might become small around the grain boundaries where the exchange fields are decreased owing to the smaller coordination number. wave function of the 4f electrons, and N R is the density of RE ions. Note that the CEF parameter

Research paper thumbnail of Effect Temperature On Fluorine Doped Tin Oxide Via Spray Pyrolysis Technique

International Journal of Scientific & Engineering Research, 2019

s. The synthesis of fluorine doped tin oxide thin films were successfully deposited onto well cle... more s. The synthesis of fluorine doped tin oxide thin films were successfully deposited onto well cleared glass substrate by varying the deposition temperature. The XRD patterns of the films showed that the deposited films are polycrystalline in nature having the characteristic peaks of tetragonal structure of SnO2.The peaks observed are (110), (101), (200), (211) and the preferential growth along the (110) direction. The current versus voltage plots of the material deposited with 380 0 C, 390 0 C and 400 o C, which represent sample FT4-FT6 showed a non-linear plot. It was observed to be non Ohmic semiconducting material. It was also noticed that as the temperature of the depositing material increases the thickness of the films increases. The resistivity of the material deposited decreases as the temperature and thickness of the films increases. It was observed that as the optical absorbance and reflectance decreases the wavelength of the incident radiation increases and transmittance increases as the wavelength of the incident radiation increases. The films deposited at 380 0 C, 390 0 C and 400 o C recorded energy gap of 2.6eV-3.0eV.

Research paper thumbnail of Corrected Conference Paper

The Temperature dependence of semiconductor energy gap has been theoretically investigated using ... more The Temperature dependence of semiconductor energy gap has been theoretically investigated using the Varshni Model. This involved a theoretical simulation of variation in fundamental energy gaps for aluminum (Al), galium (Ga) and gallium arsenide (GaAs) using MATLAB programme at temperature ranges of 0-300 K. The result showed that, as temperature increased the top of the valence band and the bottom of the conduction band increased, while the energy band gap decreased.

Research paper thumbnail of Theoretical Evaluation of Temperature Dependence of Energy Gap for Aluminum, Gallium and Gallium Arsenide

The Temperature dependence of semiconductor energy gap has been theoretically investigated using ... more The Temperature dependence of semiconductor energy gap has been theoretically investigated using the
Varshni Model. This involved a theoretical simulation of variation in fundamental energy gaps for
aluminum (Al), galium (Ga) and gallium arsenide (GaAs) using MATLAB programme at temperature
ranges of 0-300 K. The result showed that, as temperature increased the top of the valence band and the
bottom of the conduction band increased, while the energy band gap decreased.