Hexagons become the secondary pattern if symmetry is broken.

Pattern formation on the free surface of a magnetic fluid subjected to a magnetic field is investigated experimentally. By tilting the magnetic field, the symmetry can be broken in a controllable manner. When increasing the amplitude of the tilted field, the flat surface gives way to liquid ridges. A further increase results in a hysteretic transition to a pattern of stretched hexagons. The instabilities are detected by means of a linear array of magnetic Hall sensors and compared with theoretical predictions.

Glasslike relaxation of labyrinthine domain patterns.

A spatial analysis of globally disordered (labyrinthine) stripe domain patterns in thin ferrimagnetic garnet films is applied to investigate the pattern evolution. After demagnetization of the sample we obtain a branched (fernlike) structure. By periodic modulation of the magnetic field the number of the branches diminishes and a labyrinthine pattern develops. We describe the evolution of the pattern by a measure extracted from the curvature of the border line of the magnetic domains. The relaxation of this measure is found to be nonexponential and can be described by the Kohlrausch-Williams-Watts law.

Oscillatory decay at the Rosensweig instability: experiment and theory.

Transient patterns of the Rosensweig instability are accessed with a pulse sequence. The critical scaling behavior of the oscillation frequency and of the propagation velocity of these patterns is experimentally investigated by switching the magnetic induction to subcritical values. The experimental findings are in good agreement with the linear theory, if the low viscosity and the finite thickness of the magnetic liquid layer are taken into account. In this way we elucidate the subcritical branch of the underlying steady state bifurcation, which is situated in the immediate vicinity of a splitting type bifurcation.