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The Ferrum Gadolinium (FeGd) material is considered an important alloy because it can induce a uniaxial anisotropy axis in the plane of the film. The alloy of Fe/Gd bilayer is good for use as a material in the manufacture of HDD because it can be applied as a magnetic storage medium with high density and heat resistance. Micromagnetic simulations were performed on antiferromagnetic Gd material, ferromagnetic Fe and Fe/Gd bilayer to determine the Neel temperature value, Curie temperature and hysteresis curve. Simulations were carried out using Vampire software with variations in the size of the side of the cube used, namely 10 nm, 17.16 nm, and 23 nm. The simulation results show in the Fe/Gd bilayer, the Curie temperature value is smaller than the Curie temperature value for ferromagnetic Fe material because there is an antiferromagnetic Gd material which acts as a pinning direction of magnetization in the ferromagnetic layer above it through anisotropy exchange. The characteristics of the hysteresis curve in the bilayer Fe/Gd material produce a smaller coercivity field value than the ferromagnetic Fe material coercivity field. This is due to the addition of an antiferromagnetic layer which greatly affects the magnetic properties of the material. [ABSTRACT FROM AUTHOR]

We have systematically investigated the ground state domain structure transition on magnetite (Fe3O4) material using micromagnetic simulation. A spherical model of magnetite nanoparticle was simulated with varied diameter size from 40 nm to 100 nm. It is observed that the domain structure transition from single domain to multi-domain occurred between 68 nm and 69 nm. The changing of domain structure is followed by changing the magnetization energy. For a single domain particle, it is observed that the demagnetization energy is dominant to exchange energy while the opposite occurs in multi-domain particle. Then, we have also calculated the critical diameter based on Brown and Kittel formulas. Comparing to the formulas, our micromagnetic results are in the range between Brown and Kittel prediction, which are 62.9 nm and 83 nm, respectively. Therefore, the observed domain structure substitution from single to multi domain structure in this study is related to the critical diameter, which the magnetization energy system changed. [ABSTRACT FROM AUTHOR]

In this work, we have systematically investigated the polarization and distance effect of Ag-NPs double sphere to localized surface plasmon resonance (LSPR) using metallic nanoparticles simulation based on boundary element approximation. Two way polarizations were applied to Ag-NPs double sphere, in parallel and perpendicular polarizations. LSPR profile generally shifted to red-shift as the diameter of Ag-NPs increased both in parallel and perpendicular polarizations. Concerning the polarization direction, we have found that LSPR shifted to blue-shift as the distance of Ag-NPs double sphere increased in parallel polarization, while LSPR shifted to red-shift in perpendicular polarization. The phenomenon can be explained by the dipole-dipole coupling interaction between Ag-NPs double sphere. The results showed that the LPSR profile was not only affected by the diameter size and the distance of Ag-NPs double sphere but also by the polarization direction. [ABSTRACT FROM AUTHOR]

In this work, we have systematically investigated the spectra localized surface plasmon (LSPR) and the plasmonic resonance sensitivity of the silver nanoparticles (Ag-NPs) coated polyvinyl alcohol (PVA) by means of numerical study based on BHMie approximation with respect to the diameter of Ag-NPs, the thickness of PVA and the refractive index of medium variation. Lorentz-Lorentz approximation was used to calculate the refractive index of medium variation. The results showed that the LSPR spectra of Ag-NPs shifted to longer wavelength or red-shift as the diameter of Ag-NPs and the thickness of PVA increased. Then, we calculated the plasmonic resonance sensitivity from the spectra of Ag-NPs coated PVA by changing the refractive index of medium. Interestingly, the plasmonic resonance sensitivity of Ag-NPs coated PVA was exponentially decreased as the thickness of PVA increased. All results showed that the spectra of Ag-NPs was affected not only by the size of Ag-NPs and the thickness of PVA but also by the medium properties. [ABSTRACT FROM AUTHOR]

We have investigated the domain wall dynamic around the Walker breakdown field in ferromagnetic nanowires by means of micromagnetic simulation. The simulation is driven by short magnetic pulse 1-ns length with a systematic variation of applied magnetic strength. Interestingly, it is found that the domain wall structure exhibits transverse domain wall structure before the Walker breakdown field while the vortex/antivortex domain wall structure after the Walker breakdown field. The domain wall velocity increases as the applied field strength increases before the Walker breakdown field and decreases after the Walker breakdown field. The Walker breakdown field decreases as the width and the thickness of nanowires increases. We also analyzed the energy magnetization density system around the Walker breakdown field. It is revealed that the magnetostatic energy dominates of the energy system and the exchange energy tendency increases as the vortex/antivortex structures is formed in ferromagnetic nanowires. [ABSTRACT FROM AUTHOR]

We have investigated dynamics susceptibility spectrum in diamond-shaped ferromagnetics Cobalt and Permalloy by means of micromagnetic simulation based on Landau-Lifshitz-Gilbert equation. Interesting, it is found that the susceptibility spectrum exhibits similar peak frequency as the diagonal of diamond-shaped increases and tends to deceases as the thickness increases. We have also examined the susceptibility spectrum of diamondshaped ferromagnetics using the Kittel's formula for frequency resonance. Our simulation results show agree well to the formula. [ABSTRACT FROM AUTHOR]

We have systematically investigated the ground state domain structure transition on magnetite (Fe3O4) material using micromagnetic simulation. A spherical model of magnetite nanoparticle was simulated with varied diameter size from 40 nm to 100 nm. It is observed that the domain structure transition from single domain to multi-domain occurred between 68 nm and 69 nm. The changing of domain structure is followed by changing the magnetization energy. For a single domain particle, it is observed that the demagnetization energy is dominant to exchange energy while the opposite occurs in multi-domain particle. Then, we have also calculated the critical diameter based on Brown and Kittel formulas. Comparing to the formulas, our micromagnetic results are in the range between Brown and Kittel prediction, which are 62.9 nm and 83 nm, respectively. Therefore, the observed domain structure substitution from single to multi domain structure in this study is related to the critical diameter, which the magnetization energy system changed. [ABSTRACT FROM AUTHOR]