Observation and modeling of ordered structures of magnetic fluid films under perpendicular magnetic fields

Structures of magnetic columns were observed to investigate the interaction of the magnetic columns under magnetic fields. The magnetic columns shown an ordered hexagonal pattern in the magnetic fluid flim under perpendicular magnetic fields H with various sweep rates dH/dt. At a fixed sweep rate, die distance between two neighboring columns was found to decrease with increasing H. Interactions among the magnetic columns were considered to establish the correlation between the column distance d and the applied magnetic field H. By combining the experimental data with the theoretical results, if was found that the dipole interactions govern the d-H behavior in the region where thermal energy is negligible. In addition, the finite size of the magnetic columns plays a role in the dipole interaction.