Untwisted magnetization

Longitudinal magnetization measurements of an untwisted composite submitted to a constant transverse induction. 

Magnetization measurements were made on untwisted composites at the last stage of the drawing process, just before the twisting process. To ensure that the filaments would be in a metallurgical state as close as possible to the one achieved after twisting, the samples were cold drawn to a final diameter the same as that of filaments in a twisted composite. 

Fig. 7. Azimuthal current density in the filaments of an untwisted 1045-NbTi filament composite calculated from axial magnetization measurements.

As mentioned earlier, the helical structure of the smectic C phase should be untwisted by an electric or magnetic field, or suppressed by a surface effect, to observe ferroelectric properties of the phase. In the first publication on ferroelectric liquid crystals [5] an approach to nontwisted ferroelectric LC materials was suggested. By mixing two individual ferroelectric liquid crystals having opposite signs of P but different absolute values, one can compensate the helical twisting without zeroing the polarization. That has been done for low-molar-mass liquid crystals... 

Physically, the rotational transformation is to untwist the twisted helical structure, so that in the rotating frame the medium now appears to be a simple birefringent material with a dielectric tensor Tj. = R T(2) R independent of z. This technique is analogous to the rotational-transformation technique used in magnetic resonance. After the transformation, Eq. (2) becomes... 

FIGURE 6.14. Schematic representation of the untwisting of a cholesteric helix by a magnetic field. 

Figure 33. Schematic representation of the untwisting of a chiral nematic helix for a magnetic field H normal to the helix axis (z) with A f>0. A denotes regions where the helix becomes distorted and B denotes regions of 180° twist walls. For the helix has...

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