Parameter dependence of two-dimensional ordered structures in magnetic fluid thin films subjected to perpendicular fields

Chin-Yih Hong¹ - C. H. Ho¹ - H. E. Horng² - Chun-Hui Chen² - S. Y. Yang³ - Y. P. Chiu² - H. C. Yang³

¹ Department of Mechanical Engineering, Da-Yeh University, Chang-Hwa 515, Taiwan
² Department of Physics, National Taiwan Normal University, Taipei 117, Taiwan
³ Department of Physics, National Taiwan University, Taipei 106, Taiwan

Abstract
When a magnetic fluid thin film is subjected to a magnetic field perpendicular to the plane of the film, a portion of magnetic particles is condensed out from the initially mono-dispersed magnetic fluid and form magnetic columns. These columns evolve from a disordered column phase to a two-dimensional ordered structural pattern as the field strength increases further. The ordered structural pattern can be characterized by the distance between columns occupying the vertices of the structural lattice. The character distance can be affected by several parameters, such as the applied magnetic field strength, the sweep rate of the field, the thickness of the magnetic fluid thin film, the concentration of magnetic fluids, and the fluid temperature. In this work, we will demonstrate the character distance of the ordered structures as functions of these control parameters. The results show that an increase of the field strength, the sweep rate and of the concentration of the magnetic fluid reduces the character distance. On the other hand, the thickness of the thin film and the temperature of the fluid tend to increase the distance. Figs 6, Refs 8.