Magnetic field induced deformations

It has been shown that the magnetic field induced deformations the macroorder... 

Recently, there has been considerable interest in soft materials with uniform magnetic field-induced deformation (Bacri et al., 1982,1983 Dean et al, 2011 Patel et ai, 2008). 

S.3.4.3 Magnetic field-induced deformation of magnetic fluid-fixed gels... 

Here nd are elastic constants. The first, is associated with a splay deformation, K2 is associated with a twist deformation and with bend (figure C2.2.11). These three elastic constants are termed the Frank elastic constants of a nematic phase. Since they control the variation of the director orientation, they influence the scattering of light by a nematic and so can be determined from light-scattering experiments. Other techniques exploit electric or magnetic field-induced transitions in well-defined geometries (Freedericksz transitions, see section (C2.2.4.1I [20, M]. 

A second possible cause of spurious ringing which is limited only to some solids is piezoelectric resonance of the sample. (Of course the cause need not be limited to a sample. More on this later.) A piezoelectric crystal has the property that a mechanical deformation of the material takes place in the presence of an electric field. Therefore, an acoustic ringing can be induced in a piezoelectric material located within an NMR probe by the rf electric field associated with the rf magnetic field. Such a ringing due to piezoelectricity has the distinguishing property that it is independent of the applied magnetic field intensity in contrast with the magnetic field induced effect described in the first part of this section. 

Magnetic field induced large deformation. By turning the magnetic field (H) on and off, the gel deforms instantly. 

It is convenient to change the variable z in Eq. (72) to one involving the director deformation 0, and for a magnetic field-induced Freedericksz transition, Eq. (57) can be... 

The magnetic field-induced director deformations involving bend or splay are illustrated in Figure 7.5b. 

The two principle modes of the magnetostriction (A -° and As or Xy-2) introduced above are illustrated in fig. 2. With respect to the non-magnetic fictitious state, a spherical, isotropic sample exhibits a relative volume change AV/V = A" 0, when it becomes magnetic. In addition, when one forces the moments to be directed along an applied magnetic field B, an anisotropic deformation is induced, which transfers the sphere into an ellipsoid with the same volume. 

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