  Using Langevin dynamics simulations, we investigate the self-assembly of
magnetic nanogels in the presence of applied magneticfields of moderate
strength. We find that even weak fields lead to drastic changes in the
structure factors of both, the embeddedmagnetic nanoparticles and of whole
nanogel particles. Nanogels assemble by uniting magnetic particle clusters
forming inter-gelbridges. At zero field the average amount of such bridges for
a pair of nanogels is close to one, whereas even for weak fields itfastly
doubles. Rapid growth of cluster size at low values of the applied field is
followed by a broad region of slow increase, causedby the mechanical
constraints imposed the polymer matrix. The influence of the latter manifests
itself in both, the slow growth ofthe magnetisation curve at intermediate
fields and the slow decay of the total Zeeman energy.
