  We combine experiments and theory to investigate the dynamics and
orientational fluctuations of ferromagnetic microellipsoids that form a
ribbon-like structure due to attractive dipolar forces. When assembled in the
ribbon, the ellipsoids displays orientational thermal uctuations with an
amplitude that can be controlled via application of an in-plane magnetic field.
We use video microscopy to investigate the orientational dynamics in real
time/space. Theoretical arguments are used to derive an analytical expression
that describes how the distribution of the different angular configurations
depends on the strength of the applied field. The experimental data are in good
agreement with the developed model for all the range of field parameters
explored. Understanding the role of uctuations in chains composed of dipolar
particles is important not only from a fundamental point of view, but it may
also help understanding the stability of such structures against thermal noise,
which is relevant in micro uidics and lab-on-a-chip applications.
