Figure 3.

(a) F_z, the z component of the force, on a 2.8-μm magnetic particle with H_x = 50 Oe and H_z = 0. With H_z = 0 the two traps (A and B) are formed at opposite ends of the disk along the x-axis. The lack of complete symmetry of the energy profile of traps A and B arises from the magnetization of the disk being not perfectly symmetric in the OOMMF simulation. (b) Potential energy profiles of traps A and B for H_z = 0. (c) The attractive force from trap A decreases with increasing H_z, with the reverse response for trap B.