The temperature behaviour of a ferroelectric smectic mixture and the detection of ferroelectric switching by NMR

The orientational order of a ferroelectric mixture has been measured by proton NMR. The alignment of the mesogenic units is reflected in the splitting of the NMR signal into a doublet. Up to a cell thickness of 200 μm, it was possible to produce well-oriented layers in the bookshelf geometry by magnetic orientation of the substances in the B₀-field. The angular dependences of the line width of the NMR signal on the tilt angle of the director have been calculated. A ferroelectric switching was detected by measuring the angular dependence of the line width in the switched state. The tilt angle and the orientational order parameter S of the bookshelf samples were estimated at various temperatures.