  Embedding magnetic colloidal particles in an elastic polymer matrix leads to
smart soft materials that can reversibly be addressed from outside by external
magnetic fields. We discover a pronounced nonlinear superelastic stress-strain
behavior of such materials using numerical simulations. This behavior results
from a combination of two stress-induced mechanisms: a detachment mechanism of
embedded particle aggregates as well as a reorientation mechanism of magnetic
moments. The superelastic regime can be reversibly tuned or even be switched on
and off by external magnetic fields and thus be tailored during operation.
Similarities to the superelastic behavior of shape-memory alloys suggest
analogous applications, with the additional benefit of reversible switchability
and a higher biocompatibility of soft materials.
