Magnetic media diamagnetic

The tendency of the magnetic lines of force to pass through a medium relative to their tendency to pass through a vacuum is the magnetic permeability, p. This is one of the parameters that distinguishes a diamagnetic material from a paramagnetic substance. Permeability is defined as. 

In contrast to diamagnetism where the magnetic interactions between molecules can be neglected, the polarization field in the medium becomes important when discussing dielectric anisotropy (see, e.g., Bottcher< >). Maier and Meier > took this into account by applying the Onsager theory.The effective induced dipole moments per molecule along and... 

In low MW nematic liquids, the application of a magnetic field H leads to uniform alignment of the molecules owing to the diamagnetic anisotropy of the volume elements and the free mobility of the molecules. The anisotropy of the magnetic susceptibility Ax is the difference between the susceptibilities parallel and pe rpendicu-lar to the main axis of the uniaxial medium (the director n) ... 

The value of the term which arises because the medium has a finite bulk magnetic susceptibility, depends on the physical shape of the sample. For diamagnetic liquids the term is reasonably constant and small - certainly much less than the experimental error in studies of chlorine shielding values in covalent compounds. This term may thus be neglected. 

In general, when an external field is applied to a nonpolar or polar liquid crystal, a quadratic- or linear-in-field term, respectively, must be added to the expression for the free energy density of the medium. The quadratic-in-field energy terms describe the interaction of the electric or magnetic field with the dielectric or diamagnetic anisotropy of susceptibility ... 

Reorientation of director L (or the optical axis) of the macroscopic volume of a liquid crystal under the effect of a field or flow of a liquid is Ae basis of most of the Imown electro- and magneto-optical effects. The anisotropy of the electrical and magnetic properties of the medium (dielectric constant Ae, diamagnetic susceptibility A%, electrical conductivity Aa) is the direct cause of orientation. The rearrangement processes are a function of the initial mientation of the molecules of the liquid crystal and its viscoelastic properties. The change in the c tical properties as a result of reorientation is the consequence of the optical anisotropy of liquid crystals. 

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