Applying a sufficiently strong magnetic field perpendicular to a ferrofluid interface causes fluid peaks to develop, known as the Cowley–Rosensweig perpendicular magnetic field peaking instability.4 Surface tension can be calculated from the given parameters in the schematic.
Images of the peaking instability for all four tested ferrofluid configurations at magnetic fields above the critical values for incipience of instability.
Measured Langevin magnetization curves for the three tested ferrofluids compared to the theoretical Langevin curve of Eq. (2). The slight deviations between theory and measurements is due to the distribution of particle sizes listed in Table III.
Physical and magnetic properties of the tested ferrotec ferrofluids at room temperature (Ref. 2).
Calculated surface tension values from the measured data and the tensiometer measured surface tension values (Ref. 2).
Internal critical magnetic field and surface tension of ferrofluids estimated from the measured magnetic flux density B and estimated range of the particle diameters from the Langevin curves.
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