DOI: 10.1051/jp1:1997186
J. Phys. I France 7 (1997) 711-728

Macro-Organized Patterns in Ferrofluid Layer: Experimental Studies

Florence Elias^{1, 2}, Cyrille Flament^{1, 2}, Jean-Claude Bacri^{1, 2} and S. Neveu<sup>3

1</sup>  Université Paris 7 - Denis Diderot, Unité de Formation et de Recherche de Physique, case 70.08, 2 place Jussieu, 75251 Paris Cedex 05, France
²  Laboratoire d'Acoustique et d'Optique de la Matière Condensée, case 78 URA 800 associée au CNRS et à l'Université Paris 6, 4 place Jussieu, 75252 Paris Cedex 05, France
³  Laboratoire de Physico-Chimie Inorganique, case 63 URA associée au CNRS et à l'Université Paris 6, 4 place Jussieu, 75252 Paris Cedex 05, France

(Received 26 September 1996, received in final form 20 January 1997, accepted 23 January 1997)

Abstract
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.

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