Formation of magnetic particle chains in ultra high magnetic field

Magnetic particles form chain-like clusters in a magnetic field. These chains are used to supply toner particles on a photoreceptor drum in the two-component magnetic brush development system used for high-speed and/or color laser printers. Characteristics of chains influence image quality of the printer. Although experiments had been performed in low magnetic field, characteristics in the high magnetic field are necessary to investigate actual performance of the system and thus an experiment on the chain formation has been performed in the ultra high magnetic field created by a superconducting magnet. It has been clarified that the chain length first increased and then decreased in accordance with the increase of the magnetic field. The result has been confirmed by a numerical calculation with the Distinct Element Method that included the contact force between particles, the gravitational force, and the magnetic force due to the field created by the coil and adjacent magnetized particles. Lastly, it has been discussed that the static stability of chain was determined by a minimization principle of the potential energy that consists of the gravitational and magnetic potential energy.