A novel magnetohydrodynamic experiment: Step-rotation of a nematic subjectto a magnetic field

We have studied the time-dependent behavior of the director following the s tep-rotation of a nematic sample subject to a static magnetic field. The di rector orientation has been monitored using ESR spectroscopy, and we have d eveloped a model-independent analysis of the spectra to yield the distribut ion function for the director with respect to the magnetic field. This reve als that immediately following the step-rotation the director is uniformly aligned parallel to the field and then adopts a range of orientations befor e returning to a state of uniform alignment with the director at the step-r otation angle to the field. This unusual behavior of the director is compar ed with the predictions of nematodynamic theory by employing an exact treat ment of the Leslie-Ericksen equations to calculate the time and space depen dence of the director orientation.