Magnetic dipolar interaction, effect

In solids, the averaging due to fast movement will not occur, or even if it does, occurs partially then, the effects of direct dipolar couplings can be observed [72,73], The direct magnetic dipolar interaction between nuclear spins causes a nucleus with spin projection, ml5 to produce a magnetic field in the z-axis, Bimc, at a distance, R, given by the following expression [12]... 

Hiraoka etal. [10] discuss the zero point effect of the magnetic dipolar interaction described by Holstein, Primakoff [11] as a possible mechanism of the reduction in the ferromagnetic moment at 0 K (see pp. 214, 216). The estimated high dipolar interaction suggests that it has an appreciable influence on the low temperature spin wave spectrum and in pressure-induced ferromagnetic EuSe, probably also causes a deviation of the NMR-v(T) dependence from the law at T/Tc< 1. This is expected to occur somewhere below 1.7 K [10]. 

This example shows that dipolar interactions can produce unexpected effects in systems containing polynuclear clusters, so that their complete quantitative description requires a model in which the dipolar interactions between all the paramagnetic sites of the system are explicitly taken into account. Local spin models of this kind can provide a description of the relative arrangement of the interacting centers at atomic resolution and have been worked out for systems containing [2Fe-2S] and [4Fe-4S] clusters (112, 192). In the latter case, an additional complication arises due to the delocalized character of the [Fe(III), Fe(II)] mixed-valence pair, so that the magnetic moments carried by the two sites A and B of Fig. 8B must be written... 

Figure 5.9. Effect of spin-spin dipolar interaction and an external magnetic field on triplet levels.

Under MAS the quadrupole splitting becomes time dependent, Qg = Qg (f) (see Sect. 2.3.4). This influences both the spin-locking behavior [223] and the polarization transfer [224], with the latter being further affected by the periodic modulation of the IS dipolar interaction. The effect of MAS on spin-locking of the S magnetization depends on the magnitude of the so-called adiabaticity parameter ... 

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