Supply of rotational energy to a levitated magnet by applying alternating transverse magnetic field

This research investigates generation of spin torque acting on a permanent magnet, freely levitated above a high-T_c superconductor, under alternating transverse magnetic field. Numerical results of 6-d.o.f. motion show that the magnet increases its velocity of rotation around its cylindrical axis and finally obtains steady-state rotation. This velocity depends on the frequency of the input coil current. A simplified 2-d.o.f. system with only essential terms was introduced in order to discuss the mechanism of nonlinear coupling which generates spinning in alternating magnetic field. Experimental results were in good agreement with numerical ones. These results show possibility of supplying rotational energy to a levitating magnet by applying alternating magnetic field.