  We report on localized patches of cellular hexagons observed on the surface
of a magnetic fluid in a vertical magnetic field. These patches are
spontaneously generated by jumping into the neighborhood of the unstable branch
of the domain covering hexagons of the Rosensweig instability upon which the
patches equilibrate and stabilise. They are found to co-exist in intervals of
the applied magnetic field strength parameter around this branch. We formulate
a general energy functional for the system and a corresponding Hamiltonian that
provides a pattern selection principle allowing us to compute Maxwell points
(where the energy of a single hexagon cell lies in the same Hamiltonian level
set as the flat state) for general magnetic permeabilities. Using numerical
continuation techniques we investigate the existence of localized hexagons in
the Young-Laplace equation coupled to the Maxwell equations. We find cellular
hexagons possess a Maxwell point providing an energetic explanation for the
multitude of measured hexagon patches. Furthermore, it is found that planar
hexagon fronts and hexagon patches undergo homoclinic snaking corroborating the
experimentally detected intervals. Besides making a contribution to the
specific area of ferrofluids, our work paves the ground for a deeper
understanding of homoclinic snaking of 2D localized patches of cellular
patterns in many physical systems.
