Magnetic susceptibility electric field

Fig. 78. Temperature dependence of (a) magnetic susceptibility and (b) electric conductivity (natural logarithm) for a single crystal of nominally FeSi.oo with magnetic and electric fields H, E applied parallel and perpendicular to the c axis. (After Hirahara and Murakami (274, 458).)...

The macroscopic optical responses of a medium are given by its linear and nonlinear susceptibilities that are the expansion coefficients of the material polarization, P, in terms of the Maxwell fields, E. When neglecting magnetic and electric field gradient effects, the defining equation reads [22] ... 

The nematic liquid crystal is orientationally soft, since restoring forces associated with deformation in the director field are very weak. This softness makes alignment of n in bulk samples occur even in very weak external magnetic or electric fields, F s H or E, or by interaction with boundary surfaces and flows in the liquid. This softness also allows for long wavelength thermal fluctuations in the director field. The Leslie viscosity parameters rather than the viscosity coefficients are the more natural quantities of interest for those methods that monitor the viscoelastic response of the nematic to director field modulations. Modulation of n in space and time manifests itself in variations of many bulk properties, e.g. the refractive index [27-37,41-44,48,51,94-106], electric susceptibility [38,39,107-110], or magnetic resonance spectra [40,45-47,111-113]. However, only a limited number of the viscosity parameters/coefficients can be precisely determined by these methods. 

Electric polarization produced by an applied electric field (electric susceptibility) Magnetization produced by an applied magnetic field (magnetic susceptibility) Electric current density produced by an applied electric field (electrical conductivity) Heat flux produced by a temperature gradient (thermal conductivity)... 

The atomic properties satisfy the necessary physical requirement of paralleling the transferability of their charge distributions - atoms that look the same in two molecules contribute identical amounts to all properties in both molecules, including field-induced properties. Thus the atoms of theory recover the experimentally measurable contributions to the volume, heats of formation, electric polarizability, and magnetic susceptibility in those cases where the group contributions are found to be transferable, as well as additive additive [4], The additivity of the atomic properties coupled with the observation that their transferability parallels the transferability of the atom s physical form are unique to QTAIM and are essential for a theory of atoms in molecules that purports to explain the observations of experimental chemistry. 

Analogous quantities to die electric moments can be defined when the external perturbation takes the form of a magnetic field. In this instance die first derivative defines the permanent magnetic moment (always zero for non-degenerate electronic states), the second derivative the magnetizability or magnetic susceptibility, etc. 

The use of an electric field is not the only effective way to influence the LC polymer structure, magnetic fields displays a closely similar effect167 168). It is interesting as a method allowing to orient LC polymers, as well as from the viewpoint of determining some parameters, such as the order parameter, values of magnetic susceptibility, rotational viscosity and others. Some relationships established for LC polymer 1 (Table 15), its blends with low-molecular liquid crystals and partially deuterated polyacrylate (polymer 4, Table 15) specially synthesized for NMR studies can be summarized as follows ... 

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