Analysis of uniaxial alignment behavior of nonmagnetic materials under static magnetic field with sample rotation

A high magnetic field is a useful tool to control the crystal alignment of nonmagnetic materials such as metals, ceramics and polymers. However, the uniaxial alignment of hexagonal crystals with a magnetic susceptibility of chi(c) < chi(a) cannot be achieved under a static magnetic field, because the c-axis could lie along any arbitrary direction in the plane perpendicular to the direction of the magnetic field. For the uniaxial alignment of these materials, the imposition of a rotating magnetic field during a slip casting process has been proposed. In this study, both theoretical analysis and model experiment have been conducted for the elucidation of the crystal alignment phenomena under a rotating magnetic field and for the quantitative clarification of the optimum operating parameters such as magnetic field strength and viscosity of the medium surrounding the crystals. It has been found that the alignment time decreased with the magnetic field strength and/or with an increase in the viscosity of the surrounding medium. This relation is in contrary to the case of the crystal alignment under the static magnetic field. The result of the model experiment agrees well with that obtained by the theoretical analysis.