Casimir torque and force in anisotropic saturated ferrite three-layer structure.

Based on the scattering formalism and transfer matrix method, we calculate the Casimir energy in multilayer system containing general anisotropic media and apply the result to the anisotropic saturated ferrite three-layer structure. We investigate the stable equilibrium resulting from repulsive Casimir force in the three-layer anisotropic ferrite structure, focusing on the control of the equilibrium position by means of the external magnetic field, which might provide possibility for Casimir actuation under external manipulation. Furthermore, we propose a Casimir torque switch where the torque acting on the intermediate layer can be switched on and off by tuning the relative orientation between the external magnetic fields applied on the outer ferrite layers. The relation between the feature of torque-off/torque-on state and the weak/strong anisotropy of the ferrite is studied. These findings suggest potential application of Casimir torque in, e.g., cooling the rotation of a thin slab in micromachining process via external magnetic field.