Magnetic Anisotropy and Magnetization Distribution

French workers have studied the 1H- and 13C-NMR parameters of disubstituted selenophenes.37 38 The proton chemical shifts are discussed in terms of magnetic anisotropy and electric field effects of the substituents in order to study the conformational equilibrium of the carbonyl group. The relationship between the H- and 13C-chemical shifts and 7t-electron distribution calculated by the PPP method are examined. Shifts and coupling constants are discussed in additivity terms. 

Anisotropy in the distribution of orientations of emitters always exists in macroscopic anisotropic media, crystals and media undergoing the effect of orienting external, mechanical, electrical or magnetic fields. Recently, the PL method has been... 

The analysis which we have just given ignores the internal anisotropy of the ferrofluid particle. It is instructive to review a calculation of Shliomis [16-18] which considers the static susceptibility in a monodis-persed colloid taking account of the internal anisotropy of the particles. The direction of the magnetization vector will be represented by r = Ml and the direction of the internal anisotropy axis by n. The equilibrium distribution function of the orientations taking account of the internal anisotropy and the applied DC field is... 

One basic problem (which has already been pointed out in sect. 3.2.2) of the fast fluctuation limit is that a separation of ( B ) and tc is not possible. Furthermore, since the expression (58) for the different directional components i contain diflerent correlation times T, it is incorrect to express the total relaxation simply as ( B Tc in a strongly anisotropic case. Therefore, from a measurement of A and Ax it is not trivial (among other considerations, one must know the muon interstitial site) to determine how much of the anisotropy comes from an anisotropic field distribution and how much relates to anisotropic fluctuation rates. One may hope that not too close to the magnetic transition (i.e., well inside the paramagnetic regime) ( fiu ) shows little anisotropy and that one senses the anisotropy of tc in ZF. But an exact treatment of a p.SR measurement on these terms has not been given to our knowledge. 

When the Fe layer thickness is reduced to 1.3 nm, the Fe Mossbauer spectra change drastically as shown in Fig. 5.5 [9]. The spectra at 4.2 K show a broad line profile, and those at 300 K have more paramagnetic-like features. As in the case of Fe/Mg multilayers already shown in Sect. 5.3.1, thin Fe layers become amorphous with reduced magnetic transition temperature and wide distribution of hyperfine fields. The perpendicular magnetic anisotropy appears at 4.2 K in these multilayers as well, which is clearly evidenced from the intensity ratio of the No. 2 and 5 lines in the spectra. 

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