  Magnetic tweezers are crucial for single-molecule and atomic
characterization, and biomedical isolation of microparticle carriers. The
trapping component of magnetic tweezing can be relying on a magnetic potential
well that can confine the relevant species to a localized region. Here, we
report that magnetic microparticles with tailored anisotropy can transition
from localized off-axis gyration to large-area locomotion in a rotating
magnetic trap. The microparticles, consisting of assemblies of magnetic cores,
are observed to either rotate about its structural geometric center or gyrate
about one of the magnetic cores, the switching of which can be modulated by the
external field. Raising the magnetic field strength above a threshold, the
particles can go beyond the traditional synchronous-rotation and
asynchronous-oscillation modes, and into a scenario of large-area circular
motion. This results in peculiar retrograde locomotion related to the
magnetization maxima of the microparticle. Our finding suggests the important
role of the microparticle's magnetic morphology in the controlled transport of
microparticles and developing smart micro-actuators and micro-robot devices.
