Magnetic coupling internal field

Conversion of magnetic hyperfine coupling constants A into internal fields for Fe When the nuclear spin is decoupled from the electronic spin by application of an external field, the hyperfine coupling, according to (4.76), is defined as... 

The experimental inertial moments may also be affected by mechanisms other than the rovib interaction discussed above e.g., by contributions from large-amplitude internal motions or by the coupling of the molecular angular momentum and spin momenta caused by the presence of internal magnetic or electric fields. We shall assume in this review that these generally much smaller effects have been... 

The differences in the population and depopulation rate constants and the phosphorescence probabilities of the three components of the triplet states form the basis of all the methods for Optical Detection of Magnetic Resonance in triplet states of jr-electron systems. These methods were developed after the discovery of optical spin polarisation and extended to inorganic solids. The essential physical difference from the optical double resonance in atoms developed by Alfred Kastler is to be found in the selection mechanism in optical double resonance, the polarisation of the resonant UV light, i.e. the symmetry of an applied field, is responsible for the selection. In optical spin polarisation, the selection is due to the spin-orbit coupling, and thus to an internal field. 

The magnitude of the spontaneous magnetization M in ordered magnets is temperature dependent due to spin wave excitations. Spin wave frequencies are so fast (THz) that they are fully motional-narrowed in jxSR. All one will observe is the expectation value of the internal field which is coupled (but not necessarily directly proportional) to the expectation value of M T). For this reason one calls the of an ordered magnet a quasistatic field. The spontaneous precession vanishes at a second-order magnetic transition point and reaches a saturation value for T —> 0. An example is shown in fig. 27. 

Displacements Aw of sublattices differ finm zero only in the presence of internal stress, in particular, in magnetic and electric fields. The parameter matrices B T) and B T) represent renormalized coefficients of the linear magnetoelastic coupling ... 

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