Via hexagons to squares in ferrofluids: experiments on hysteretic surface transformations under variation of the normal magnetic field

Gollwitzer, Christian; Rehberg, Ingo; Richter, R.

doi:10.1088/0953-8984/18/38/s08

Cited by 23 publications

(24 citation statements)

References 34 publications

(53 reference statements)

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“…For higher inductions a transition from hexagonal to square symmetry is predicted [6,7] and found experimentally [14]. Figure 7 shows the final state.…”

Section: Squaresmentioning

confidence: 56%

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Mag(net)ic Liquid Mountains

Richter

2011

Europhysics News

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“…For higher inductions a transition from hexagonal to square symmetry is predicted [6,7] and found experimentally [14]. Figure 7 shows the final state.…”

Section: Squaresmentioning

confidence: 56%

“…With this coding we unveil that the squares appear in patches. is block-wise transformation may be again a consequence of a wave front locking [14].…”

Section: " "mentioning

confidence: 99%

Mag(net)ic Liquid Mountains

Richter

2011

Europhysics News

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“…(Gollwitzer et al, 2006). For sake of simplicity, we assume that the cell has a circular shape of radius a inscribed to a hexagonal cell of the pattern, see Fig.…”

Section: Numerical Methods and Toolsmentioning

confidence: 99%

Numerical Study of Diffusion of Interacting Particles in a Magnetic Fluid Layer

Lavrova¹,

Полевиков²,

Tobiska³

2012

Numerical Modelling

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“…To distinguish between them, we used a criterion formulated in Ref. [20]. We perform a Voronoi-like analysis for each particle position and measure the average area hai and perimeter h Q i of the Voronoi cells for all particles in the cluster.…”

Section: Prl 100 148304 (2008) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

Colloidal Assembly on Magnetically Vibrated Stripes

et al. 2008

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We investigate the collective organization of paramagnetic colloidal particles externally driven above the periodic stripes of a uniaxial ferrimagnetic garnet film. An external field modulation induces vibration of the stripe walls and produces random motion of the particles. Defects in the stripe pattern break the symmetry of the potential and favor particle nucleation into large clusters above a critical density. Mismatch between particle size and pattern wavelength generates assemblies with different morphological order. At even higher field strengths, repulsive dipolar interactions between the particles induce cluster melting. We propose a novel approach to generate and externally control a variety of colloidal assemblies. DOI: 10.1103/PhysRevLett.100.148304 PACS numbers: 82.70.Dd, 64.60.Qÿ Application of an electric, magnetic, or vibrating drive to a collection of interacting particles in two dimensions (2D) leads to a rich variety of aggregated phases [1,2]. Such studies provide means to understand more general problems in condensed matter like crystal formation, atomic diffusion, or phase transitions. Significant examples include colloidal particles under ac electric fields [3,4], magnetic particles under external modulations [5,6], and vibrating granular media [7,8]. While an external homogeneous field imposed on the particle ensemble elicits global responses, spatially periodic potentials can act individually on the particles allowing a more precise control over their mutual interactions. Optical tweezers [9] or structured magnetic substrates [10] can be used to generate heterogeneous potentials on the colloidal length scale. In the latter case, a ferrimagnetic garnet film with stripe domains provides a 1D periodic pinning landscape on which one can trap [10] or move [11] arrays of paramagnetic particles. In the last case, the interplay between magnetic interactions and viscous damping is the crucial factor of the particle behavior. By further reducing the spatial length scale of the confining potential, we here demonstrate that a time periodic magnetic driving force leads to an ordered aggregation of colloidal particles. This aggregation thermally relaxes after turning off the applied field. Moreover, controlled reversibility (assembly or disassembly) is gained by externally varying the amplitude of the imposed magnetic modulation.We study the induced aggregation of paramagnetic colloids deposited on a garnet film having alternating ferromagnetic domains with wavelength smaller and incommensurate with respect to the particle size. Externally induced vibration of the domain walls (DWs) causes random particle motion on the surface. By increasing the particle concentration, we observe cluster formation around regions where high stripe curvature or point defects break the symmetry of the periodic potential. By varying the intensity and frequency of the external magnetic field, we observe a variety of morphological assemblies and report on the system full phase diagram. At higher field strengths, cluste...

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Via hexagons to squares in ferrofluids: experiments on hysteretic surface transformations under variation of the normal magnetic field

Cited by 23 publications

References 34 publications

Mag(net)ic Liquid Mountains

Mag(net)ic Liquid Mountains

Numerical Study of Diffusion of Interacting Particles in a Magnetic Fluid Layer

Colloidal Assembly on Magnetically Vibrated Stripes

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