Zero-temperature Monte Carlo simulations are used to investigate the hysteresis of a magnetic particle ina dipolarIsing model. The magnetic particle is described in a system of permanent dipoles, and the dipoles are l...Zero-temperature Monte Carlo simulations are used to investigate the hysteresis of a magnetic particle ina dipolarIsing model. The magnetic particle is described in a system of permanent dipoles, and the dipoles are locatedin a cubic lattice site. The effects of the shape and the size of the particle on the hysteresis loop at zero temperatureare obtained. For strong exchange interactions, the shapes of magnetic hysteresis loops approach rectangle. For weakexchange interactions, the effects of the size and the shape of the particle on the loops are more remarkable than thoseof strong exchange interactions case. The slope of the hysteresis loop decreases with the increase of the ratio of thesemi major axis to the semi minor axis of the ellipsoidal magnetic particle, and there is an increase of the slope of thehysteresis with the decrease of the size of the magnetic particle. The effects of the shape and size of the particle on thecoercive force at zero temperature are also investigated.展开更多
We report on a forest-like-to-desert-like pattern evolution in the growth of an organic thin film observed by using an atomic force microscope. We use a modified diffusion limited aggregation model to simulate the gro...We report on a forest-like-to-desert-like pattern evolution in the growth of an organic thin film observed by using an atomic force microscope. We use a modified diffusion limited aggregation model to simulate the growth process and are able to reproduce the experimental patterns. The energy of electric dipole interaction is calculated and determined to be the driving force for the pattern formation and evolution. Based on these results, single crystalline films are obtained by enhancing the electric dipole interaction while limiting effects of other growth parameters.展开更多
This paper proposes a simple model for studying ferroelectricity by introducing a screened dipole dipole interaction Hamiltonian. By minimizing the total energy, the body centered tetragonal lattice structure is sho...This paper proposes a simple model for studying ferroelectricity by introducing a screened dipole dipole interaction Hamiltonian. By minimizing the total energy, the body centered tetragonal lattice structure is shown to be stable under the screened dipole dipole interaction, while the cubic structure is not. The effectiveness of this model is estimated by simplifying the model to the nearest neighbor Ising model for evaluating the physical quantities. The results are in qualitative agreement with experimental data. A method is also suggested to verify the results. In addition, the critical temperature of the 3D Ising model for body centered tetragonal crystals is obtained using the Monte Carlo method.展开更多
文摘Zero-temperature Monte Carlo simulations are used to investigate the hysteresis of a magnetic particle ina dipolarIsing model. The magnetic particle is described in a system of permanent dipoles, and the dipoles are locatedin a cubic lattice site. The effects of the shape and the size of the particle on the hysteresis loop at zero temperatureare obtained. For strong exchange interactions, the shapes of magnetic hysteresis loops approach rectangle. For weakexchange interactions, the effects of the size and the shape of the particle on the loops are more remarkable than thoseof strong exchange interactions case. The slope of the hysteresis loop decreases with the increase of the ratio of thesemi major axis to the semi minor axis of the ellipsoidal magnetic particle, and there is an increase of the slope of thehysteresis with the decrease of the size of the magnetic particle. The effects of the shape and size of the particle on thecoercive force at zero temperature are also investigated.
基金Project supported by the National Natural Science Foundation of China (Grant No.10774176)the National Basic Research Program of China (Grant No.2006CB806202)
文摘We report on a forest-like-to-desert-like pattern evolution in the growth of an organic thin film observed by using an atomic force microscope. We use a modified diffusion limited aggregation model to simulate the growth process and are able to reproduce the experimental patterns. The energy of electric dipole interaction is calculated and determined to be the driving force for the pattern formation and evolution. Based on these results, single crystalline films are obtained by enhancing the electric dipole interaction while limiting effects of other growth parameters.
文摘This paper proposes a simple model for studying ferroelectricity by introducing a screened dipole dipole interaction Hamiltonian. By minimizing the total energy, the body centered tetragonal lattice structure is shown to be stable under the screened dipole dipole interaction, while the cubic structure is not. The effectiveness of this model is estimated by simplifying the model to the nearest neighbor Ising model for evaluating the physical quantities. The results are in qualitative agreement with experimental data. A method is also suggested to verify the results. In addition, the critical temperature of the 3D Ising model for body centered tetragonal crystals is obtained using the Monte Carlo method.
