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Gavin S. Abo,Yang-Ki Hong,Jeevan Jalli,Jaejin Lee,Jihoon Park,Seok Bae,Seong-Gon Kim,Byoung-Chul Choi,Terumitsu Tanaka 한국자기학회 2012 Journal of Magnetics Vol.17 No.1
The coercivity of a single 27 nm-spherical barium ferrite (S-BaFe) particle was simulated using three models: 1) Gibbs free energy (GFE), 2) Landau-Lifshitz-Gilbert (LLG), and 3) Stoner-Wohlfarth (S-W). Spherically and hexagonally shaped particles were used in the GFE and LLG simulations to investigate coercivity with the different shape anisotropies. The effect of shape was not included in the S-W model. It was found that the models using a spherical shape resulted in a coercivity higher than the models using the hexagonal shape with both shapes having the same diameter. The coercivity estimated with the S-W model was approximately the same as that for the spherical-shape models, which indicates that spherical shape has no significant effect on the particle’s coercivity at nanoscale.
Seok Bae,Yang-Ki Hong,Jaejin Lee,Jihoon Park,Jeevan Jalli,Gavin S. Abo,Hyuck M. Kwon,Chandana K. K. Jayasooriya 한국자기학회 2013 Journal of Magnetics Vol.18 No.1
A pulsed ferrite magnetic field generator (FMFG) was designed for the use in the 1000 m long through-theearth (TTE) communication system for mining disaster situations. To miniaturize the TTE system, a ferrite core having 10,000 of permeability was used for the FMFG. Attenuation of the magnetic field intensity from the FMFG (200-turn and 0.18 m diameter) was calculated to be 89.95 ㏈ at 1000 m depth soil having 0.1 S/m of conductivity. This attenuation was lower than 151.13 dB attenuation of 1 ㎑ electromagnetic wave at the same conditions. Therefore, the magnetic-field was found to be desirable as a signal carrier source for TTE communications as compared to the electromagnetic wave. The designed FMFG generates the magnetic field intensity of 1 × 10?¹? Tesla at 1000 m depth. This magnetic field is detectable by compact magnetic sensors such as flux gate or magnetic tunneling junction sensor. Therefore, the miniature FMFG TTE communication system can replace the conventional electromagnetic wave carrier type TTE system and allow reliable signal transmission between rescuer and trapped miners.
Jalli, Jeevan,Hong, Yang-Ki,Bae, Seok,Lee, Jae-Jin,Abo, Gavin S.,Lyle, Andrew,Gee, Sung-Hoon,Lee, Hwachol,Mewes, Tim,Sur, Jeong-Chul,Lee, Sung-Ik American Institute of Physics 2009 JOURNAL OF APPLIED PHYSICS - Vol.105 No.7
<P>Liquid phase epitaxy technique was used to grow 144 mu m thick barium ferrite (BaFe12O19; BaM) single crystalline films on (111) Gd3Ga5O12 substrate. The growth rate of 72 mu m/h was achieved with a flux system of Fe2O3-BaCO3-Na2CO3. The grown BaM films show single crystalline (000l) orientation that was confirmed by x-ray diffraction and magnetic torque curves. The saturation magnetization (4 pi M-s) and the anisotropy field (H-k) were found to be 4.2 kG and 16.0 kOe, respectively. The ferrimagnetic resonance linewidth (Delta H) at 35 GHz was measured to be 0.1 kOe. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3062824]</P>