Papers by Keyword: Micromagnetic

Abstract: In this paper, the magnetization reversal of sphere-shaped ferromagnetic nanoparticles has been investigated by means of micromagnetic simulation. Some ferromagnetic particles such as Cobalt, Iron, Nickel, and Permalloy were modeled with size variation from 50 nm to 100 nm. The discretization of the ferromagnetic model was used a cell size of 2.5×2.5×2.5 nm³ considering the exchange length (l_ex) of the materials. The quasi-static magnetic field was induced into the nanosphere to observe the magnetization response under time dependence. It is found that the coercivity values are decreased as the sphere size increased, which was conformed the experimental results. It is also observed that the domain structure of a single particle in remanent and ground-state condition are identical. Therefore, the specific understanding of magnetization process and domain structures in ferromagnetic nanoparticles could be an important step in the development of nanopatterned magnetic memory storage.

Abstract: We have systematically investigated the dynamic susceptibility spectra of square-patterned ferromagnets in the mesoscopic scale from 100 nm to 500 nm by means of a micromagnetic simulation. The dynamic susceptibility spectra are obtained from the magnetization response under the applied field using Fourier transforms technique. We have observed that the frequency peak of the susceptibility spectra slightly increases as the length of the square-patterned increases. Interestingly, the frequency peak shows similar behavior compared to the frequency resonance from Kittel’s formula. We have also analyzed the magnetic energies, where the demagnetization energy is larger than the exchange energy. It can be explained that the polar interaction primarily contributes to the resonance mode of the square-patterned ferromagnets

Abstract: The magnetic hysteresis loops of Nd₂Fe₁₄B/α-Fe/Nd₂Fe₁₄B exchange-coupling trilayer film are simulated by micromagnetic theory, and the relationship between remanence, coercivity, energy products and soft magnetic thickness are discussed in detail. The results show that the hysteresis loops is rectangle and the trilayer films are in complete exchange-coupling region when the soft magnetic thickness is below the critical point(5nm); With the increase of the soft magnetic thickness, the coercivity of the trilayer films decreases monotonically. Maximum energy products are obtained when the soft magnetic thickness is 5nm.

Abstract: The coupling between the strain gradient and electric polarization is known as flexoelectricity in dielectrics materials. In case of magnetic media it takes the form of electric polarization induced by spin modulation and vice versa. This spin flexoelectricity causes new physical phenomena of micromagnetism such as electric field driven magnetic domain wall motion and electrical control of magnetic vortices in magnets as well as clamping of the magnetic domain walls at the ferroelectric ones in multiferroics.

Abstract: Micromagnetic simulation was carried out to investigate the behavior of ferromagnetic materials at a very small length scale, at which the materials usually exhibit different properties compared with those of the corresponding bulk materials. By solving the time and spatial dependent Landau-Lifshitz-Gilbert (LLG) equation in reciprocal space using fast Fourier transformation (FFT) technique, the equilibrium magnetization state was, thus, achieved. The hysteresis loops were also simulated, from which the relation of coercivity and characteristic length was established. Besides, the effect of external stress on coercivity was also taken into consideration. The results showed that at such length scales the external stress strongly affected the magnetic behavior of ferromagnetic materials.