A magnetic field-dependent modulation effect tends to stabilize light transmission through binary ferrofluids

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• 作者：Jian Li ; ^{aizhong@swu.edu.cn} ; Yueqiang Lin ; Xiaodong Liu ; Qingmei Zhang ; Hua Miao ; Jun Fu ; Lihua Lin
• 关键词：Ferrofluids ; Transmission light ; Chain ; Motion
• 刊名：Optics Communications
• 出版年：2012
• 出版时间：15 June, 2012
• 年：2012
• 卷：285
• 期：13-14
• 页码：3111-3115
• 全文大小：1075 K

文摘

In binary ferrofluids composed of ferromagnetic ¦Ã?Fe₂O₃/Ni₂O₃ composite nanoparticles (A particles) and noncrystalline Fe₂O₃ nanoparticles (B particles), the A particles alone will form chain-like aggregates upon application of a magnetic field. Due to both the long-range ¡®magnetic convergent force?(F_C) and the short-range ¡®magnetic divergent force?(F_D), the A-particle chains immersed in the B-particle ¡®sea?will move in a manner similar to the process of vibrational damping. The apparent damping of the ferrofluids will vary from weak to overdamping according to the motion of the chains, so that the intensity of light transmitted through a ferrofluid film along the direction of the field would tend to stabilize after a period of rapid decrements and increments. In binary ferrofluids, the B-particle system can produce a modulation effect on both the damping and the driving force, further stabilizing the behavior of the transmitted light. At low fields (e.g., 500 Gs, 900 Gs) only the modulation of the viscosity drag force (F_v) is considerable, so that overdamping increases linearly with B-particle volume fraction (§¶_B), and the variation in the transmitted light is much slower during the process tending towards stability as §¶_B increases. However, at high fields (e.g., 1300 Gs) the polarization of the B-particle ¡®sea?is enhanced, so that F_D is modulated as well as F_v (i.e., both the practical damping and driving forces are modulated simultaneously). Thus, the apparent overdamping of the binary ferrofluids system will vary non-linearly as §¶_B increases, and the transmitted light will tend to stabilize faster for ferrofluids with high ¦µ_B than for those with low §¶_B at an applied magnetic field of 1300 Gs.