Magnetoelastic interaction

Here k denotes the Boltzmann constant. In our first order approach the trace in (10) is calculated using the states of the unperturbed system, i.e. without taking into account the magnetoelastic interactions, by putting e= 0 in (3)-(6). In practice, these eigenstates of the... 

In the case, that the magnetoelastic interaction is dominated by the isotropic contribution... 

Contributions to the magnetoelastic interaction that contain the rotational tensor are important only in an external magnetic field. This will be considered separately in sect. 2.6. For the moment we consider only pure strain contributions. In cubic crystals the components of e can be grouped to form irreducible representations of the cubic point group (Thalmeier and Fulde 1975, du Tremolet de Lacheisserie et al. 1978) ... 

Fig. 24. Magnetic field dependence of the three C44 modes for T= 4.3 K in CeAlj. Full lines are strain susceptibilities for ( , k ) and (Uj, k ) modes. Broken lines indicate rota-tionally invariant magnetoelastic interaction (Liithi and Lingner 1979).

As mentioned previously this mixing of phonons and quadrupolar excitons due to magnetoelastic interactions has so far been found only in insulators but not in intermetallic R compounds. 

Fig. 33. (a) Dyson equation for the pseudofermion propagators of CEF states n, m (broken lines). Phonons are indicated by wavy lines. Open circles represent the magnetoelastic interaction vertex, (b) Bubble diagram for the dynamical magnetic susceptibility using renormalized propagators. Open squares represent the dipolar operator J. 

The lattice deformation due to two-particle magnetoelastic interactions is determined by the equations... 

---