Sánchez-Miranda M J, Carrillo-Estrada J L, Donado F
Instituto de Física "Luis Rivera Terrazas", Benemérita Universidad Autónoma de Puebla, Puebla, Puebla, Mexico.
Instituto de Ciencias Básicas e Ingeniería de la Universidad Autónoma del Estado de Hidalgo-AAMF, Pachuca, 42184, Pachuca de Soto, Mexico.
Sci Rep. 2019 Mar 5;9(1):3531. doi: 10.1038/s41598-019-40062-2.
Applying an unsteady magnetic field to a 2D nonvibrating magnetic granular system induces a random motion in the steel beads with characteristics analogous to that of molecules in a fluid. We investigate the structural characteristics of the solid-like structures generated by different quenching conditions. The applied field is generated by the superposition of a constant field and a collinear sinusoidal field. The system reaches a quasi steady state in which the effective temperature is proportional to the amplitude of the applied field. By reducing the effective temperature at different rates, different cooling rates are produced. A slight inclination of the surface allows us to investigate the effects of small particle concentration gradients. The formation of a wide and rich variety of condensed solid structures, from gel-like and glass-like structures up to crystalline structures, is observed and depends on the cooling rate. We focus our attention on the crystallization process and found this process to be a collective phenomenon. We discuss our results in terms of the measured time evolution of the mean squared displacement, the effective diffusion coefficient, and the radial distribution function.
对二维非振动磁性颗粒系统施加不稳定磁场会在钢珠中诱发随机运动，其特性类似于流体中分子的运动。我们研究了不同淬火条件下生成的类固体结构的结构特征。施加的磁场由恒定磁场和共线正弦磁场叠加产生。系统达到准稳态，其中有效温度与施加磁场的振幅成正比。通过以不同速率降低有效温度，可以产生不同的冷却速率。表面的轻微倾斜使我们能够研究小颗粒浓度梯度的影响。观察到形成了从凝胶状和玻璃状结构到晶体结构的广泛而丰富的凝聚固体结构，这取决于冷却速率。我们将注意力集中在结晶过程上，发现这个过程是一种集体现象。我们根据测量的均方位移、有效扩散系数和径向分布函数的时间演化来讨论我们的结果。
