Macro-Organized Patterns in Ferrofluid Layer: Experimental Studies

We present some experimental results concerning the conformational instabilities observed in a thin layer made of an immiscible mixture of a magnetic fluid and another liquid submitted to an external magnetic field. We observed macroscopic domains with stripe or bubble shape. The transition between the two morphologies is observed and a coexistence of the two phases is visualized in a variable thickness layer. Furthermore, we give other results about the instabilities of the parallel stripe pattern: by increasing the external field the stripe pattern becomes a chevron structure, which also becomes unstable for higher values of the magnetic field and gives a hairpin pattern. Finally, we present a new system: a magnetic liquid froth in two dimensions which is analogous to soap froths with an additional external control parameter, the magnetic field.